{"task_id": "2012_q1g", "description": "Consider the function f shown in the Karnaugh map below. Implement this function.\n// x[1]x[2]\n// x[3]x[4] 00 01 11 10\n// 00 | 1 | 0 | 0 | 1 |\n// 01 | 0 | 0 | 0 | 0 |\n// 11 | 1 | 1 | 1 | 0 |\n// 10 | 1 | 1 | 0 | 1 |", "module_header": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n", "original_code": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n always @(*) begin\n case ({x4, x3, x2, x1})\n 4'b0000: f = 1'b0;\n 4'b0001: f = 1'b0;\n 4'b0011: f = 1'b1;\n 4'b0010: f = 1'b1;\n 4'b0110: f = 1'b1;\n 4'b0111: f = 1'b1;\n 4'b0101: f = 1'b0;\n 4'b0100: f = 1'b0;\n 4'b1100: f = 1'b1;\n 4'b1101: f = 1'b1;\n 4'b1111: f = 1'b1;\n 4'b1110: f = 1'b0;\n 4'b1010: f = 1'b1;\n 4'b1011: f = 1'b0;\n 4'b1001: f = 1'b0;\n 4'b1000: f = 1'b1;\n endcase\n end\n\nendmodule", "error": "6: error: Unable to bind wire/reg/memory `x1' in `top_module'\n6: error: Unable to bind wire/reg/memory `x2' in `top_module'\n6: error: Unable to bind wire/reg/memory `x3' in `top_module'\n6: error: Unable to bind wire/reg/memory `x4' in `top_module'\n6: error: Unable to elaborate this case expression.\n6: error: Concatenation/replication may not have zero width in this context.\n"} {"task_id": "2012_q1g", "description": "Consider the function f shown in the Karnaugh map below. Implement this function.\n// x[1]x[2]\n// x[3]x[4] 00 01 11 10\n// 00 | 1 | 0 | 0 | 1 |\n// 01 | 0 | 0 | 0 | 0 |\n// 11 | 1 | 1 | 1 | 0 |\n// 10 | 1 | 1 | 0 | 1 |", "module_header": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n", "original_code": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n logic [1:0] x21;\n logic [1:0] x12;\n logic [1:0] x20;\n logic [1:0] x10;\n\n assign x21 = {x[2], x[1]};\n assign x12 = {x[1], x[2]};\n assign x20 = {x[2], x[0]};\n assign x10 = {x[1], x[0]};\n\n always_comb begin\n case (x21)\n 2'b00: f = 1;\n 2'b01: f = 0;\n 2'b10: f = 0;\n 2'b11: f = 1;\n endcase\n end\n\nendmodule", "error": "13: warning: Constant bit select [0] is before vector x[4:1].\n13: : Replacing select with a constant 1'bx.\n12: : Replacing select with a constant 1'bx.\n12: warning: Constant bit select [0] is before vector x[4:1].\n"} {"task_id": "2012_q2b", "description": "\n// Consider the state machine shown below:\n\n// A (0) --1--> B\n// A (0) --0--> A\n// B (0) --1--> C\n// B (0) --0--> D\n// C (0) --1--> E\n// C (0) --0--> D\n// D (0) --1--> F\n// D (0) --0--> A\n// E (1) --1--> E\n// E (1) --0--> D\n// F (1) --1--> C\n// F (1) --0--> D\n\n// Assume that a one-hot code is used with the state assignment y[5:0] = 000001(A), 000010(B), 000100(C), 001000(D), 010000(E), 100000(F)\n\n// Write a Verilog for the signal Y1, which is the input of state flip-flop y[1], for the signal Y3, which is the input of state flip-flop y[3]. Derive the Verilog by inspection assuming a one-hot encoding.\n", "module_header": "module top_module (\n\tinput [5:0] y,\n\tinput w,\n\toutput Y1,\n\toutput Y3\n);\n", "original_code": "module top_module (\n\tinput [5:0] y,\n\tinput w,\n\toutput Y1,\n\toutput Y3\n);\n reg Y1;\n reg Y3;\n\n always @(posedge w)\n begin\n case (y)\n 6'b000001: Y1 <= 1'b0;\n 6'b000010: Y1 <= 1'b1;\n 6'b000100: Y3 <= 1'b1;\n 6'b001000: Y3 <= 1'b0;\n 6'b010000: Y3 <= 1'b0;\n 6'b100000: Y3 <= 1'b1;\n endcase\n end\n\n assign Y1 = y[1];\n assign Y3 = y[3];\n\nendmodule", "error": "4: : It was declared here as a net.\n8: error: 'Y3' has already been declared in this scope.\n5: : It was declared here as a net.\n7: error: 'Y1' has already been declared in this scope.\n"} {"task_id": "2012_q2b", "description": "\n// Consider the state machine shown below:\n\n// A (0) --1--> B\n// A (0) --0--> A\n// B (0) --1--> C\n// B (0) --0--> D\n// C (0) --1--> E\n// C (0) --0--> D\n// D (0) --1--> F\n// D (0) --0--> A\n// E (1) --1--> E\n// E (1) --0--> D\n// F (1) --1--> C\n// F (1) --0--> D\n\n// Assume that a one-hot code is used with the state assignment y[5:0] = 000001(A), 000010(B), 000100(C), 001000(D), 010000(E), 100000(F)\n\n// Write a Verilog for the signal Y1, which is the input of state flip-flop y[1], for the signal Y3, which is the input of state flip-flop y[3]. Derive the Verilog by inspection assuming a one-hot encoding.\n", "module_header": "module top_module (\n\tinput [5:0] y,\n\tinput w,\n\toutput Y1,\n\toutput Y3\n);\n", "original_code": "module top_module (\n\tinput [5:0] y,\n\tinput w,\n\toutput Y1,\n\toutput Y3\n);\n\n // Y1 is the input of state flip-flop y[1]\n assign Y1 = y1;\n\n // Y3 is the input of state flip-flop y[3]\n assign Y3 = y3;\n\nendmodule", "error": "12: error: Unable to elaborate r-value: y3\n12: error: Unable to bind wire/reg/memory `y3' in `top_module'\n9: error: Unable to bind wire/reg/memory `y1' in `top_module'\n9: error: Unable to elaborate r-value: y1\n"} {"task_id": "2012_q2fsm", "description": "Consider the state machine shown below:\n\n// A (0) --1--> B\n// A (0) --0--> A\n// B (0) --1--> C\n// B (0) --0--> D\n// C (0) --1--> E\n// C (0) --0--> D\n// D (0) --1--> F\n// D (0) --0--> A\n// E (1) --1--> E\n// E (1) --0--> D\n// F (1) --1--> C\n// F (1) --0--> D\n\n// Reset resets into state A and is synchronous active-high. \n\n// Write complete Verilog code that represents this FSM. Use separate **always** blocks for the state table and the state flip-flops. Describe the FSM output, which is called _z_, using either continuous assignment statement(s) or an **always** block (at your discretion). Assign any state codes that you wish to use.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n // Define state codes\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b01;\n parameter F = 2'b10;\n\n // Define state flip-flops\n reg [1:0] state;\n always @(posedge clk) begin\n if (reset) begin\n state <= A;\n end else begin\n case (state)\n A: begin\n if (w) begin\n state <= B;\n end else begin\n state <= A;\n end\n end\n B: begin\n if (w) begin\n state <= C;\n end else begin\n state <= D;\n end\n end\n C: begin\n if (w) begin\n state <= E;\n end else begin\n state <= D;\n end\n end\n D: begin\n if (w) begin\n state <= F;\n end else begin\n state <= A;\n end\n end\n E: begin\n if (w) begin\n state <= E;\n end else begin\n state <= D;\n end\n end\n F: begin\n if (w) begin\n state <= C;\n end else begin\n state <= D;\n end\n end\n endcase\n end\n end\n\n // Define state table\n always @(*) begin\n case (state)\n A: z = 1'b0;\n B: z = 1'b0;\n C: z = 1'b0;\n D: z = 1'b0;\n E: z = 1'b1;\n F: z = 1'b0;\n endcase\n end\n\nendmodule", "error": "71: error: 'z' is not a valid l-value for a procedural assignment.\n76: error: 'z' is not a valid l-value for a procedural assignment.\n72: error: 'z' is not a valid l-value for a procedural assignment.\n5: : 'z' is declared here as a wire.\n73: error: 'z' is not a valid l-value for a procedural assignment.\n75: error: 'z' is not a valid l-value for a procedural assignment.\n74: error: 'z' is not a valid l-value for a procedural assignment.\n"} {"task_id": "2012_q2fsm", "description": "Consider the state machine shown below:\n\n// A (0) --1--> B\n// A (0) --0--> A\n// B (0) --1--> C\n// B (0) --0--> D\n// C (0) --1--> E\n// C (0) --0--> D\n// D (0) --1--> F\n// D (0) --0--> A\n// E (1) --1--> E\n// E (1) --0--> D\n// F (1) --1--> C\n// F (1) --0--> D\n\n// Reset resets into state A and is synchronous active-high. \n\n// Write complete Verilog code that represents this FSM. Use separate **always** blocks for the state table and the state flip-flops. Describe the FSM output, which is called _z_, using either continuous assignment statement(s) or an **always** block (at your discretion). Assign any state codes that you wish to use.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n // Define state codes\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n parameter F = 2'b101;\n\n // Define state flip-flops\n reg [2:0] state;\n\n // Define state table\n always @(posedge clk) begin\n // always block triggered on positive edge of clock signal.\n if (reset) begin\n // If reset signal is high.\n state <= A; // Set state to A.\n end else begin\n // If reset signal is low.\n case (state)\n // Switching between states.\n A: if (w) state <= B; else state <= A; // Transition based on input w.\n B: if (w) state <= C; else state <= D; // Transition based on input w.\n C: if (w) state <= E; else state <= D; // Transition based on input w.\n D: if (w) state <= F; else state <= A; // Transition based on input w.\n E: if (w) state <= E; else state <= D; // Transition based on input w.\n F: if (w) state <= C; else state <= D; // Transition based on input w.\n endcase\n end\n end\n\n // Define output\n assign z = (state == E); // Output z is high when state is E.\n\nendmodule", "error": "13: warning: Numeric constant truncated to 2 bits.\n13: warning: Extra digits given for sized binary constant.\n12: warning: Numeric constant truncated to 2 bits.\n12: warning: Extra digits given for sized binary constant.\n"} {"task_id": "2013_q2afsm", "description": "Consider the FSM described by the state diagram shown below:\n\n// A --r1=0,r2=0,r3=0--> A\n// A --r1=1--> B\n// A --r1=0,r2=1--> C\n// A --r1=0,r2=0,r3=0--> D\n// B (g1=1) --r1=1--> B\n// B (g1=1) --r1=0--> A\n// C (g2=1) --r2=1--> C\n// C (g2=1) --r2=0--> A\n\n// Resetn is an active-low synchronous reset that resets into state A. This FSM acts as an arbiter circuit, which controls access to some type of resource by three requesting devices. Each device makes its request for the resource by setting a signal _r[i]_ = 1, where _r[i]_ is either _r[1]_, _r[2]_, or _r[3]_. Each r[i] is an input signal to the FSM, and represents one of the three devices. The FSM stays in state _A_ as long as there are no requests. When one or more request occurs, then the FSM decides which device receives a grant to use the resource and changes to a state that sets that device's _g[i]_ signal to 1. Each _g[i]_ is an output from the FSM. There is a priority system, in that device 1 has a higher priority than device 2, and device 3 has the lowest priority. Hence, for example, device 3 will only receive a grant if it is the only device making a request when the FSM is in state _A_. Once a device, _i_, is given a grant by the FSM, that device continues to receive the grant as long as its request, _r[i]_ = 1.\n\n// Write complete Verilog code that represents this FSM. Use separate always blocks for the state table and the state flip-flops, as done in lectures. Describe the FSM outputs, _g[i]_, using either continuous assignment statement(s) or an always block (at your discretion). Assign any state codes that you wish to use.", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput [3:1] r,\n\toutput [3:1] g\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput [3:1] r,\n\toutput [3:1] g\n);\n // Define state codes\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n\n // Define state flip-flops\n reg [1:0] state;\n always @(posedge clk or negedge resetn) begin\n // always block triggered on positive edge of clock signal or negative edge of reset signal.\n if (!resetn) begin\n // If reset signal is active low.\n state <= A; // Set state to A.\n end else begin\n // If reset signal is not active low.\n case (state)\n // Switching between states.\n A: begin\n if (r[1] && !r[2] && !r[3]) begin\n // If condition for state transition from A to B.\n state <= B; // Move to state B.\n end else if (!r[1] && r[2] && !r[3]) begin\n // If condition for state transition from A to C.\n state <= C; // Move to state C.\n end else if (!r[1] && !r[2] && r[3]) begin\n // If condition for state transition from A to D.\n state <= D; // Move to state D.\n end\n end\n B: begin\n if (r[1]) begin\n // If condition for state transition from B to B.\n state <= B; // Stay in state B.\n end else begin\n // If condition for state transition from B to A.\n state <= A; // Move to state A.\n end\n end\n C: begin\n if (r[2]) begin\n // If condition for state transition from C to C.\n state <= C; // Stay in state C.\n end else begin\n // If condition for state transition from C to A.\n state <= A; // Move to state A.\n end\n end\n D: begin\n if (r[3]) begin\n // If condition for state transition from D to D.\n state <= D; // Stay in state D.\n end else begin\n // If condition for state transition from D to A.\n state <= A; // Move to state A.\n end\n end\n endcase\n end\n end\n\n // Define state table\n always @(*) begin\n // Combinational logic based on current state.\n case (state)\n // Switching between states.\n A: begin\n g[1] = 0; // Grant to device 1.\n g[2] = 0; // Grant to device 2.\n g[3] = 0; // Grant to device 3.\n end\n B: begin\n g[1] = 1; // Grant to device 1.\n g[2] = 0; // Grant to device 2.\n g[3] = 0; // Grant to device 3.\n end\n C: begin\n g[1] = 0; // Grant to device 1.\n g[2] = 1; // Grant to device 2.\n g[3] = 0; // Grant to device 3.\n end\n D: begin\n g[1] = 0; // Grant to device 1.\n g[2] = 0; // Grant to device 2.\n g[3] = 1; // Grant to device 3.\n end\n endcase\n end\n\nendmodule", "error": "73: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n80: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd1]' is declared here as a wire.\n79: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n83: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n85: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd2]' is declared here as a wire.\n75: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n78: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n88: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n84: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n74: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n89: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n90: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd3]' is declared here as a wire.\n"} {"task_id": "2013_q2afsm", "description": "Consider the FSM described by the state diagram shown below:\n\n// A --r1=0,r2=0,r3=0--> A\n// A --r1=1--> B\n// A --r1=0,r2=1--> C\n// A --r1=0,r2=0,r3=0--> D\n// B (g1=1) --r1=1--> B\n// B (g1=1) --r1=0--> A\n// C (g2=1) --r2=1--> C\n// C (g2=1) --r2=0--> A\n\n// Resetn is an active-low synchronous reset that resets into state A. This FSM acts as an arbiter circuit, which controls access to some type of resource by three requesting devices. Each device makes its request for the resource by setting a signal _r[i]_ = 1, where _r[i]_ is either _r[1]_, _r[2]_, or _r[3]_. Each r[i] is an input signal to the FSM, and represents one of the three devices. The FSM stays in state _A_ as long as there are no requests. When one or more request occurs, then the FSM decides which device receives a grant to use the resource and changes to a state that sets that device's _g[i]_ signal to 1. Each _g[i]_ is an output from the FSM. There is a priority system, in that device 1 has a higher priority than device 2, and device 3 has the lowest priority. Hence, for example, device 3 will only receive a grant if it is the only device making a request when the FSM is in state _A_. Once a device, _i_, is given a grant by the FSM, that device continues to receive the grant as long as its request, _r[i]_ = 1.\n\n// Write complete Verilog code that represents this FSM. Use separate always blocks for the state table and the state flip-flops, as done in lectures. Describe the FSM outputs, _g[i]_, using either continuous assignment statement(s) or an always block (at your discretion). Assign any state codes that you wish to use.", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput [3:1] r,\n\toutput [3:1] g\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput [3:1] r,\n\toutput [3:1] g\n);\n // State codes\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n\n // State flip-flops\n reg [1:0] state;\n always @(posedge clk, negedge resetn) begin\n if (!resetn) begin\n state <= A;\n end else begin\n case (state)\n A: begin\n if (r[1] || r[2] || r[3]) begin\n if (r[1] && !r[2] && !r[3]) begin\n state <= B;\n end else if (!r[1] && r[2] && !r[3]) begin\n state <= C;\n end else if (!r[1] && !r[2] && r[3]) begin\n state <= D;\n end\n end\n end\n B: begin\n if (r[1] || r[2] || r[3]) begin\n if (r[1] && !r[2] && !r[3]) begin\n state <= B;\n end else if (!r[1] && r[2] && !r[3]) begin\n state <= C;\n end else if (!r[1] && !r[2] && r[3]) begin\n state <= D;\n end\n end else begin\n state <= A;\n end\n end\n C: begin\n if (r[1] || r[2] || r[3]) begin\n if (r[1] && !r[2] && !r[3]) begin\n state <= B;\n end else if (!r[1] && r[2] && !r[3]) begin\n state <= C;\n end else if (!r[1] && !r[2] && r[3]) begin\n state <= D;\n end\n end else begin\n state <= A;\n end\n end\n D: begin\n if (r[1] || r[2] || r[3]) begin\n if (r[1] && !r[2] && !r[3]) begin\n state <= B;\n end else if (!r[1] && r[2] && !r[3]) begin\n state <= C;\n end else if (!r[1] && !r[2] && r[3]) begin\n state <= D;\n end\n end else begin\n state <= A;\n end\n end\n endcase\n end\n end\n\n // State table\n always @(*) begin\n case (state)\n A: begin\n g[1] = 0;\n g[2] = 0;\n g[3] = 0;\n end\n B: begin\n g[1] = 1;\n g[2] = 0;\n g[3] = 0;\n end\n C: begin\n g[1] = 0;\n g[2] = 1;\n g[3] = 0;\n end\n D: begin\n g[1] = 0;\n g[2] = 0;\n g[3] = 1;\n end\n endcase\n end\n\nendmodule", "error": "80: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n79: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd1]' is declared here as a wire.\n83: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n85: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd2]' is declared here as a wire.\n78: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n88: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n84: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n89: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n90: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n94: error: 'g['sd2]' is not a valid l-value for a procedural assignment.\n95: error: 'g['sd3]' is not a valid l-value for a procedural assignment.\n5: : 'g['sd3]' is declared here as a wire.\n93: error: 'g['sd1]' is not a valid l-value for a procedural assignment.\n"} {"task_id": "2013_q2bfsm", "description": "Consider a finite state machine that is used to control some type of motor. The FSM has inputs x and y, which come from the motor, and produces outputs f and g, which control the motor. There is also a clock input called clk and a reset input (synchronous, active low) called resetn. The FSM has to work as follows. As long as the reset input is asserted, the FSM stays in a beginning state, called state A. When the reset signal is de-asserted, then after the next clock edge the FSM has to set the output f to 1 for one clock cycle. Then, the FSM has to monitor the x input. When x has produced the values 1, 0, 1 in three successive clock cycles, then g should be set to 1 on the following clock cycle. While maintaining g = 1 the FSM has to monitor the y input. If y has the value 1 within at most two clock cycles, then the FSM should maintain g = 1 permanently (that is, until reset). But if y does not become 1 within two clock cycles, then the FSM should set g = 0 permanently (until reset).", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput x,\n\tinput y,\n\toutput f,\n\toutput g\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput x,\n\tinput y,\n\toutput f,\n\toutput g\n);\n parameter A = 2'b00, B = 2'b01, C = 2'b10, D = 2'b11;\n reg [1:0] state, next_state;\n reg [1:0] x_prev, y_prev;\n reg [1:0] x_prev_prev, y_prev_prev;\n reg [1:0] count;\n reg g_prev;\n wire g;\n assign g = g_prev;\n reg f_prev;\n wire f;\n assign f = f_prev;\n\n always @(posedge clk or negedge resetn) begin\n if (!resetn) begin\n state <= A;\n x_prev <= 2'b00;\n y_prev <= 2'b00;\n x_prev_prev <= 2'b00;\n y_prev_prev <= 2'b00;\n count <= 2'b00;\n g_prev <= 1'b0;\n f_prev <= 1'b0;\n end else begin\n state <= next_state;\n x_prev_prev <= x_prev;\n x_prev <= x;\n y_prev_prev <= y_prev;\n y_prev <= y;\n count <= count + 1;\n if (x == 1) begin\n count <= 2'b01;\n end else if (x != x_prev) begin\n count <= 2'b00;\n end\n if (y == 1 && count <= 2) begin\n g_prev <= 1'b1;\n end else begin\n g_prev <= 1'b0;\n end\n if (state == C) begin\n f_prev <= 1'b1;\n end else begin\n f_prev <= 1'b0;\n end\n end\n end\n\n always @(*) begin\n case (state)\n A: begin\n next_state = B;\n f_prev = 1'b0;\n end\n B: begin\n next_state = C;\n f_prev = 1'b1;\n end\n C: begin\n next_state = D;\n f_prev = 1'b0;\n end\n D: begin\n next_state = A;\n f_prev = 1'b0;\n end\n endcase\n end\n\nendmodule", "error": "15: error: 'g' has already been declared in this scope.\n18: error: 'f' has already been declared in this scope.\n7: : It was declared here as a net.\n6: : It was declared here as a net.\n"} {"task_id": "2013_q2bfsm", "description": "Consider a finite state machine that is used to control some type of motor. The FSM has inputs x and y, which come from the motor, and produces outputs f and g, which control the motor. There is also a clock input called clk and a reset input (synchronous, active low) called resetn. The FSM has to work as follows. As long as the reset input is asserted, the FSM stays in a beginning state, called state A. When the reset signal is de-asserted, then after the next clock edge the FSM has to set the output f to 1 for one clock cycle. Then, the FSM has to monitor the x input. When x has produced the values 1, 0, 1 in three successive clock cycles, then g should be set to 1 on the following clock cycle. While maintaining g = 1 the FSM has to monitor the y input. If y has the value 1 within at most two clock cycles, then the FSM should maintain g = 1 permanently (that is, until reset). But if y does not become 1 within two clock cycles, then the FSM should set g = 0 permanently (until reset).", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput x,\n\tinput y,\n\toutput f,\n\toutput g\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput x,\n\tinput y,\n\toutput f,\n\toutput g\n);\n parameter A = 2'b00, B = 2'b01, C = 2'b10, D = 2'b11;\n reg [1:0] state, next_state;\n\n reg [1:0] count;\n reg [1:0] next_count;\n\n reg f_reg, g_reg;\n\n always @(posedge clk) begin\n if (!resetn) begin\n state <= A;\n count <= 2'b00;\n f_reg <= 1'b0;\n g_reg <= 1'b0;\n end\n else begin\n state <= next_state;\n count <= next_count;\n f_reg <= f;\n g_reg <= g;\n end\n end\n\n always @(*) begin\n case (state)\n A: begin\n f = 1'b0;\n g = 1'b0;\n next_state = B;\n next_count = 2'b00;\n end\n B: begin\n f = 1'b1;\n g = 1'b0;\n next_state = C;\n next_count = 2'b00;\n end\n C: begin\n f = 1'b0;\n g = 1'b0;\n next_state = D;\n next_count = 2'b00;\n end\n D: begin\n f = 1'b0;\n g = 1'b0;\n if (x == 1) begin\n next_state = D;\n next_count = count + 1;\n end\n else begin\n next_state = A;\n next_count = 2'b00;\n end\n end\n endcase\n end\n\n always @(*) begin\n if (y == 1) begin\n g = 1'b1;\n end\n else begin\n g = 1'b0;\n end\n end\n\n always @(*) begin\n if (count == 2'b11) begin\n f = 1'b1;\n end\n else begin\n f = 1'b0;\n end\n end\n\nendmodule", "error": "69: error: 'g' is not a valid l-value for a procedural assignment.\n7: : 'g' is declared here as a wire.\n78: error: 'f' is not a valid l-value for a procedural assignment.\n72: error: 'g' is not a valid l-value for a procedural assignment.\n42: error: 'g' is not a valid l-value for a procedural assignment.\n47: error: 'f' is not a valid l-value for a procedural assignment.\n81: error: 'f' is not a valid l-value for a procedural assignment.\n6: : 'f' is declared here as a wire.\n36: error: 'g' is not a valid l-value for a procedural assignment.\n41: error: 'f' is not a valid l-value for a procedural assignment.\n48: error: 'g' is not a valid l-value for a procedural assignment.\n54: error: 'g' is not a valid l-value for a procedural assignment.\n53: error: 'f' is not a valid l-value for a procedural assignment.\n35: error: 'f' is not a valid l-value for a procedural assignment.\n"} {"task_id": "2014_q3c", "description": "Given the state-assigned table shown below, implement the logic functions Y[0] and z.\n// Present state y[2:0] | Next state Y[2:0] x=0, Next state Y[2:0] x=1 | Output z\n// 000 | 000, 001 | 0\n// 001 | 001, 100 | 0\n// 010 | 010, 001 | 0\n// 011 | 001, 010 | 1\n// 100 | 011, 100 | 1\n", "module_header": "module top_module (\n\tinput clk,\n\tinput x,\n\tinput [2:0] y,\n\toutput reg Y0,\n\toutput reg z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput x,\n\tinput [2:0] y,\n\toutput reg Y0,\n\toutput reg z\n);\n wire [2:0] next_state_x0;\n wire [2:0] next_state_x1;\n wire [2:0] current_state;\n\n // Mapping to next state Y[2:0] x=0\n always @(*) begin\n case (y)\n 3'b000: next_state_x0 = 3'b000;\n 3'b001: next_state_x0 = 3'b001;\n 3'b010: next_state_x0 = 3'b001;\n 3'b011: next_state_x0 = 3'b010;\n 3'b100: next_state_x0 = 3'b011;\n default: next_state_x0 = 3'b000;\n endcase\n end\n\n // Mapping to next state Y[2:0] x=1\n always @(*) begin\n case (y)\n 3'b000: next_state_x1 = 3'b001;\n 3'b001: next_state_x1 = 3'b100;\n 3'b010: next_state_x1 = 3'b001;\n 3'b011: next_state_x1 = 3'b010;\n 3'b100: next_state_x1 = 3'b100;\n default: next_state_x1 = 3'b000;\n endcase\n end\n\n // Current state\n always @(posedge clk) begin\n current_state <= y;\n end\n\n // Output Y0\n always @(*) begin\n case (current_state)\n 3'b000: Y0 = next_state_x0[0];\n 3'b001: Y0 = next_state_x0[1];\n 3'b010: Y0 = next_state_x0[0];\n 3'b011: Y0 = next_state_x0[1];\n 3'b100: Y0 = next_state_x0[1];\n default: Y0 = 1'b0;\n endcase\n end\n\n // Output z\n always @(*) begin\n case (current_state)\n 3'b000: z = next_state_x1[0];\n 3'b001: z = next_state_x1[1];\n 3'b010: z = next_state_x1[0];\n 3'b011: z = next_state_x1[1];\n 3'b100: z = next_state_x1[1];\n default: z = 1'b0;\n endcase\n end\n\nendmodule", "error": "30: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n18: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n19: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n20: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n8: : 'next_state_x0' is declared here as a wire.\n16: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n27: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n9: : 'next_state_x1' is declared here as a wire.\n29: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n32: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n38: error: 'current_state' is not a valid l-value for a procedural assignment.\n10: : 'current_state' is declared here as a wire.\n17: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n28: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n31: error: 'next_state_x1' is not a valid l-value for a procedural assignment.\n15: error: 'next_state_x0' is not a valid l-value for a procedural assignment.\n"} {"task_id": "2014_q3c", "description": "Given the state-assigned table shown below, implement the logic functions Y[0] and z.\n// Present state y[2:0] | Next state Y[2:0] x=0, Next state Y[2:0] x=1 | Output z\n// 000 | 000, 001 | 0\n// 001 | 001, 100 | 0\n// 010 | 010, 001 | 0\n// 011 | 001, 010 | 1\n// 100 | 011, 100 | 1\n", "module_header": "module top_module (\n\tinput clk,\n\tinput x,\n\tinput [2:0] y,\n\toutput reg Y0,\n\toutput reg z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput x,\n\tinput [2:0] y,\n\toutput reg Y0,\n\toutput reg z\n);\n\n reg [3:0] prev_state, next_state;\n reg [2:0] curr_state;\n reg [2:0] next_state_y2;\n reg [2:0] next_state_y1;\n reg [2:0] next_state_y0;\n reg [2:0] Y0_next;\n reg [2:0] Y1_next;\n reg [2:0] Y2_next;\n reg [2:0] z_next;\n reg [1:0] y_prev;\n reg [1:0] y_next;\n reg [1:0] x_prev;\n reg [1:0] x_next;\n\n always @(posedge clk) begin\n if (prev_state == 4'b0000) begin\n curr_state <= 3'b000;\n end else begin\n curr_state <= prev_state[3:1];\n end\n if (y[2:1] == 2'b00) begin\n next_state_y2 <= 3'b000;\n next_state_y1 <= 3'b001;\n next_state_y0 <= 3'b000;\n end else if (y[2:1] == 2'b01) begin\n next_state_y2 <= 3'b001;\n next_state_y1 <= 3'b100;\n next_state_y0 <= 3'b000;\n end else if (y[2:1] == 2'b10) begin\n next_state_y2 <= 3'b010;\n next_state_y1 <= 3'b001;\n next_state_y0 <= 3'b000;\n end else begin // y[2:1] == 2'b11\n next_state_y2 <= 3'b001;\n next_state_y1 <= 3'b010;\n next_state_y0 <= 3'b001;\n end\n Y0_next <= curr_state[2];\n Y1_next <= next_state_y1[2];\n Y2_next <= next_state_y2[2];\n z_next <= next_state_y0[2];\n if (x == 1'b0) begin\n Y0 <= Y0_next;\n Y1 <= Y1_next;\n Y2 <= Y2_next;\n z <= z_next;\n end else begin // x == 1'b1\n Y0 <= y[2];\n Y1 <= y[1];\n Y2 <= y[0];\n z <= 1'b1;\n end\n x_next <= x;\n y_next <= y;\n prev_state <= {x_prev, y_prev, curr_state[2:0], z};\n x_prev <= x_next;\n y_prev <= y_next;\n end\nendmodule", "error": "57: error: Could not find variable ``Y1'' in ``top_module''\n53: error: Could not find variable ``Y2'' in ``top_module''\n58: error: Could not find variable ``Y2'' in ``top_module''\n52: error: Could not find variable ``Y1'' in ``top_module''\n"} {"task_id": "2014_q3fsm", "description": "Consider a finite state machine with inputs s and w. Assume that the FSM begins in a reset state called A, as depicted below. The FSM remains in state A as long as s = 0, and it moves to state B when s = 1. Once in state B the FSM examines the value of the input w in the next three clock cycles. If w = 1 in exactly two of these clock cycles, then the FSM has to set an output z to 1 in the following clock cycle. Otherwise z has to be 0. The FSM continues checking w for the next three clock cycles, and so on. Use as few states as possible. Note that the s input is used only in state A, so you need to consider just the w input. Assume reset is active high synchronous.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput s,\n\tinput w,\n\toutput reg z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput s,\n\tinput w,\n\toutput reg z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n parameter F = 2'b101;\n parameter G = 2'b110;\n parameter H = 2'b111;\n parameter I = 2'b1000;\n parameter J = 2'b1001;\n parameter K = 2'b1010;\n parameter L = 2'b1011;\n parameter M = 2'b1100;\n parameter N = 2'b1101;\n parameter O = 2'b1110;\n parameter P = 2'b1111;\n\n reg [3:0] state, next_state;\n\n always @ (posedge clk or posedge reset) begin\n if (reset) begin\n state <= A;\n z <= 0;\n end else begin\n state <= next_state;\n case (state)\n A: begin\n if (s == 1) begin\n next_state <= B;\n end else begin\n next_state <= A;\n end\n end\n B: begin\n if (w == 1) begin\n next_state <= C;\n end else begin\n next_state <= B;\n end\n end\n C: begin\n if (w == 1) begin\n next_state <= D;\n end else begin\n next_state <= B;\n end\n end\n D: begin\n if (w == 1) begin\n next_state <= E;\n end else begin\n next_state <= B;\n end\n end\n E: begin\n if (w == 1) begin\n next_state <= F;\n end else begin\n next_state <= B;\n end\n end\n F: begin\n if (w == 1) begin\n next_state <= G;\n end else begin\n next_state <= B;\n end\n end\n G: begin\n if (w == 1) begin\n next_state <= H;\n end else begin\n next_state <= B;\n end\n end\n H: begin\n if (w == 1) begin\n next_state <= I;\n end else begin\n next_state <= B;\n end\n end\n I: begin\n if (w == 1) begin\n next_state <= J;\n end else begin\n next_state <= B;\n end\n end\n J: begin\n if (w == 1) begin\n next_state <= K;\n end else begin\n next_state <= B;\n end\n end\n K: begin\n if (w == 1) begin\n next_state <= L;\n end else begin\n next_state <= B;\n end\n end\n L: begin\n if (w == 1) begin\n next_state <= M;\n end else begin\n next_state <= B;\n end\n end\n M: begin\n if (w == 1) begin\n next_state <= N;\n end else begin\n next_state <= B;\n end\n end\n N: begin\n if (w == 1) begin\n next_state <= O;\n end else begin\n next_state <= B;\n end\n end\n O: begin\n if (w == 1) begin\n next_state <= P;\n end else begin\n next_state <= B;\n end\n end\n P: begin\n if (w == 1) begin\n next_state <= B;\n end else begin\n next_state <= A;\n end\n end\n endcase\n end\n end\n\n always @ (posedge clk or posedge reset) begin\n if (reset) begin\n z <= 0;\n end else begin\n case (state)\n B: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n C: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n D: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n E: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n F: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n G: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n H: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n I: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n J: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n K: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n L: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n M: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n N: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n O: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n P: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "16: warning: Extra digits given for sized binary constant.\n12: warning: Numeric constant truncated to 2 bits.\n19: warning: Extra digits given for sized binary constant.\n13: warning: Extra digits given for sized binary constant.\n18: warning: Extra digits given for sized binary constant.\n21: warning: Numeric constant truncated to 2 bits.\n19: warning: Numeric constant truncated to 2 bits.\n15: warning: Numeric constant truncated to 2 bits.\n17: warning: Numeric constant truncated to 2 bits.\n12: warning: Extra digits given for sized binary constant.\n22: warning: Numeric constant truncated to 2 bits.\n15: warning: Extra digits given for sized binary constant.\n13: warning: Numeric constant truncated to 2 bits.\n23: warning: Numeric constant truncated to 2 bits.\n20: warning: Extra digits given for sized binary constant.\n14: warning: Numeric constant truncated to 2 bits.\n14: warning: Extra digits given for sized binary constant.\n16: warning: Numeric constant truncated to 2 bits.\n22: warning: Extra digits given for sized binary constant.\n21: warning: Extra digits given for sized binary constant.\n18: warning: Numeric constant truncated to 2 bits.\n20: warning: Numeric constant truncated to 2 bits.\n23: warning: Extra digits given for sized binary constant.\n17: warning: Extra digits given for sized binary constant.\n"} {"task_id": "2014_q3fsm", "description": "Consider a finite state machine with inputs s and w. Assume that the FSM begins in a reset state called A, as depicted below. The FSM remains in state A as long as s = 0, and it moves to state B when s = 1. Once in state B the FSM examines the value of the input w in the next three clock cycles. If w = 1 in exactly two of these clock cycles, then the FSM has to set an output z to 1 in the following clock cycle. Otherwise z has to be 0. The FSM continues checking w for the next three clock cycles, and so on. Use as few states as possible. Note that the s input is used only in state A, so you need to consider just the w input. Assume reset is active high synchronous.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput s,\n\tinput w,\n\toutput reg z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput s,\n\tinput w,\n\toutput reg z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n\n reg [2:0] currentState;\n\n always @(posedge clk) begin\n if (reset) begin\n currentState <= A;\n z <= 0;\n end else begin\n case (currentState)\n A: begin\n if (s) begin\n currentState <= B;\n end\n end\n B: begin\n currentState <= C;\n end\n C: begin\n currentState <= D;\n end\n D: begin\n if (w == 1) begin\n currentState <= E;\n end else begin\n currentState <= B;\n end\n end\n E: begin\n if (w == 1) begin\n z <= 1;\n end else begin\n z <= 0;\n end\n currentState <= B;\n end\n endcase\n end\n end\n\nendmodule", "error": "12: warning: Numeric constant truncated to 2 bits.\n12: warning: Extra digits given for sized binary constant.\n"} {"task_id": "2014_q4a", "description": "Consider an n-bit shift register circuit. Inputs E are for enabling shift, R for value to load, L is asserted when it should load, and w is the input to the first stage of the shift register. Write a Verilog module named top_module for one stage of this circuit, including both the flip-flop and multiplexers.", "module_header": "module top_module (\n\tinput clk,\n\tinput w,\n\tinput R,\n\tinput E,\n\tinput L,\n\toutput reg Q\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput w,\n\tinput R,\n\tinput E,\n\tinput L,\n\toutput reg Q\n);\n always @(posedge clk) begin\n if (E) begin\n Q <= {Q[0], w};\n end else if (L) begin\n Q <= R;\n end\n end\n\nendmodule", "error": "11: error: can not select part of scalar: Q\n"} {"task_id": "2014_q4a", "description": "Consider an n-bit shift register circuit. Inputs E are for enabling shift, R for value to load, L is asserted when it should load, and w is the input to the first stage of the shift register. Write a Verilog module named top_module for one stage of this circuit, including both the flip-flop and multiplexers.", "module_header": "module top_module (\n\tinput clk,\n\tinput w,\n\tinput R,\n\tinput E,\n\tinput L,\n\toutput reg Q\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput w,\n\tinput R,\n\tinput E,\n\tinput L,\n\toutput reg Q\n);\n flip_flop ff(clk, E, w, Q);\n mux_2to1 mux(Q, R, L, Q);\n\nendmodule", "error": "10: error: Unknown module type: mux_2to1\n9: error: Unknown module type: flip_flop\n"} {"task_id": "7420", "description": "The 7400-series integrated circuits are a series of digital chips with a few gates each. The 7420 is a chip with two 4-input NAND gates.\n\n// Create a module with the same functionality as the 7420 chip. It has 8 inputs and 2 outputs.", "module_header": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d, \n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\n", "original_code": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d, \n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\n sky130_fd_sc_hdll__nand2_1 nand1 (\n .A(p1a),\n .B(p1b),\n .Y(p1y)\n );\n\n sky130_fd_sc_hdll__nand2_1 nand2 (\n .A(p2a),\n .B(p2b),\n .Y(p2y)\n );\n\n sky130_fd_sc_hdll__not_1 not1 (\n .A(p1y),\n .Y(p1y)\n );\n\n sky130_fd_sc_hdll__not_1 not2 (\n .A(p2y),\n .Y(p2y)\n );\n\nendmodule", "error": "19: error: Unknown module type: sky130_fd_sc_hdll__nand2_1\n30: error: Unknown module type: sky130_fd_sc_hdll__not_1\n13: error: Unknown module type: sky130_fd_sc_hdll__nand2_1\n25: error: Unknown module type: sky130_fd_sc_hdll__not_1\n"} {"task_id": "7420", "description": "The 7400-series integrated circuits are a series of digital chips with a few gates each. The 7420 is a chip with two 4-input NAND gates.\n\n// Create a module with the same functionality as the 7420 chip. It has 8 inputs and 2 outputs.", "module_header": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d, \n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\n", "original_code": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d, \n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\n wire nand1_out;\n wire nand2_out;\n\n sky130_fd_sc_hd__nand2_1 nand1 (nand1_out, p1a, p1b);\n sky130_fd_sc_hd__nand2_1 nand2 (nand2_out, p2a, p2b);\n sky130_fd_sc_hd__nand2_1 nand3 (p1y, nand1_out, p1c, p1d);\n sky130_fd_sc_hd__nand2_1 nand4 (p2y, nand2_out, p2c, p2d);\nendmodule", "error": "18: error: Unknown module type: sky130_fd_sc_hd__nand2_1\n19: error: Unknown module type: sky130_fd_sc_hd__nand2_1\n16: error: Unknown module type: sky130_fd_sc_hd__nand2_1\n17: error: Unknown module type: sky130_fd_sc_hd__nand2_1\n"} {"task_id": "7458", "description": "The 7458 is a chip with four AND gates and two OR gates. Create a module in Verilog with the same functionality as the 7458 chip. It has 10 inputs and 2 outputs. You may choose to use an `assign` statement to drive each of the output wires, or you may choose to declare (four) wires for use as intermediate signals, where each internal wire is driven by the output of one of the AND gates.\n\n// In this circuit, p1y should be the OR of two 3-input AND gates: one that ANDs p1a, p1b, and p1c, and the second that ANDs p1d, p1e, and p1f. The output p2y is the OR of two 2-input AND gates: one that ANDs p2a and p2b, and the second that ANDs p2c and p2d.", "module_header": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d,\n\tinput p1e,\n\tinput p1f,\n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\n", "original_code": "module top_module(\n\tinput p1a, \n\tinput p1b, \n\tinput p1c, \n\tinput p1d,\n\tinput p1e,\n\tinput p1f,\n\toutput p1y, \n\tinput p2a, \n\tinput p2b, \n\tinput p2c, \n\tinput p2d, \n\toutput p2y\n);\nwire p1y_temp;\n assign p1y = p1y_temp;\n always @(p1a or p1b or p1c or p1d or p1e or p1f) begin\n \tp1y_temp = (p1a & p1b & p1c) | (p1d & p1e & p1f);\n end\n\n wire p2y_temp;\n assign p2y = p2y_temp;\n always @(p2a or p2b or p2c or p2d) begin\n \tp2y_temp = (p2a & p2b) | (p2c & p2d);\n end\n\nendmodule\n", "error": "24: error: 'p2y_temp' is not a valid l-value for a procedural assignment.\n18: error: 'p1y_temp' is not a valid l-value for a procedural assignment.\n21: : 'p2y_temp' is declared here as a wire.\n15: : 'p1y_temp' is declared here as a wire.\n"} {"task_id": "always_case", "description": "Create a 6-to-1 multiplexer. When sel is between 0 and 5, choose the corresponding data input. Otherwise, output 0. The data inputs and outputs are all 4 bits wide.", "module_header": "module top_module (\n\tinput [2:0] sel,\n\tinput [3:0] data0,\n\tinput [3:0] data1,\n\tinput [3:0] data2,\n\tinput [3:0] data3,\n\tinput [3:0] data4,\n\tinput [3:0] data5,\n\toutput reg [3:0] out\n);\n", "original_code": "module top_module (\n\tinput [2:0] sel,\n\tinput [3:0] data0,\n\tinput [3:0] data1,\n\tinput [3:0] data2,\n\tinput [3:0] data3,\n\tinput [3:0] data4,\n\tinput [3:0] data5,\n\toutput reg [3:0] out\n);\n parameter DATA_WIDTH = 4;\n parameter SEL_WIDTH = 3;\n parameter NUM_DATA_INPUTS = 6;\n\n wire [DATA_WIDTH-1:0] data_inputs [0:NUM_DATA_INPUTS-1];\n wire [SEL_WIDTH-1:0] sel_input;\n assign sel_input = sel;\n\n // Assign data inputs to data_inputs array\n assign data_inputs[0] = data0;\n assign data_inputs[1] = data1;\n assign data_inputs[2] = data2;\n assign data_inputs[3] = data3;\n assign data_inputs[4] = data4;\n assign data_inputs[5] = data5;\n\n // Assign out to data_inputs[sel_input] if sel_input is within bounds, otherwise assign out to 0\n always @(*) begin\n if (sel_input >= 0 && sel_input <= NUM_DATA_INPUTS-1) begin\n out = data_inputs[sel_input];\n end else begin\n out = 0;\n end\n end\n\nendmodule", "error": "30: warning: @* is sensitive to all 6 words in array 'data_inputs'.\n"} {"task_id": "always_casez", "description": "Build a priority encoder for 8-bit inputs. Given an 8-bit vector, the output should report the first (least significant) bit in the vector that is 1. Report zero if the input vector has no bits that are high. For example, the input 8'b10010000 should output 3'd4, because bit[4] is first bit that is high.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput reg [2:0] pos\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput reg [2:0] pos\n);\n always @ (in) begin\n pos = 0;\n for (i = 0; i < 8; i = i + 1) begin\n if (in[i] == 1) begin\n pos = i;\n break;\n end\n end\n end\n\nendmodule", "error": "7: register ``i'' unknown in top_module.\n"} {"task_id": "always_casez", "description": "Build a priority encoder for 8-bit inputs. Given an 8-bit vector, the output should report the first (least significant) bit in the vector that is 1. Report zero if the input vector has no bits that are high. For example, the input 8'b10010000 should output 3'd4, because bit[4] is first bit that is high.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput reg [2:0] pos\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput reg [2:0] pos\n);\n always @ (posedge clk) begin\n if (in[0]) pos <= 0;\n else if (in[1]) pos <= 1;\n else if (in[2]) pos <= 2;\n else if (in[3]) pos <= 3;\n else if (in[4]) pos <= 4;\n else if (in[5]) pos <= 5;\n else if (in[6]) pos <= 6;\n else if (in[7]) pos <= 7;\n else pos <= 0;\n end\n\nendmodule", "error": "5: error: Failed to evaluate event expression 'posedge clk'.\n5: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "always_if", "description": "Build a 2-to-1 mux that chooses between a and b. Choose b if both sel_b1 and sel_b2 are true. Otherwise, choose a. Do the same twice, once using assign statements and once using a procedural if statement.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput sel_b1,\n\tinput sel_b2,\n\toutput out_assign,\n\toutput reg out_always\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput sel_b1,\n\tinput sel_b2,\n\toutput out_assign,\n\toutput reg out_always\n);\n assign out_assign = (sel_b1 && sel_b2) ? b : a;\n\n always @(posedge clk) begin\n if (sel_b1 && sel_b2) begin\n out_always <= b;\n end else begin\n out_always <= a;\n end\n end\n\nendmodule", "error": "11: error: Failed to evaluate event expression 'posedge clk'.\n11: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "always_if2", "description": "Fix any and all bugs in this code:\n\n// module top_module (\n// input cpu_overheated,\n// output reg shut_off_computer,\n// input arrived,\n// input gas_tank_empty,\n// output reg keep_driving ); //\n\n// always @(*) begin\n// if (cpu_overheated)\n// shut_off_computer = 1;\n// end\n\n// always @(*) begin\n// if (~arrived)\n// keep_driving = ~gas_tank_empty;\n// end\n\n// endmodule\n", "module_header": "module top_module (\n\tinput cpu_overheated,\n\toutput reg shut_off_computer,\n\tinput arrived,\n\tinput gas_tank_empty,\n\toutput reg keep_driving\n);\n", "original_code": "module top_module (\n\tinput cpu_overheated,\n\toutput reg shut_off_computer,\n\tinput arrived,\n\tinput gas_tank_empty,\n\toutput reg keep_driving\n);\n parameter C_RESET_ACTIVE = 1'b1;\n\n // synthesis attribute async_register then_port=\"*\"\n reg reset_r; \n always @ (posedge clk) begin\n if (rst) begin \n reset_r <= C_RESET_ACTIVE;\n end else begin \n reset_r <= 1'b0; \n end\n end\n\n always @ (*) begin\n if (cpu_overheated)\n shut_off_computer = 1;\n else\n shut_off_computer = reset_r;\n end\n\n always @ (*) begin\n if (~arrived)\n keep_driving = ~gas_tank_empty;\n else\n keep_driving = 1'b0;\n end\n\nendmodule", "error": "13: error: Unable to bind wire/reg/memory `rst' in `top_module'\n13: error: Unable to elaborate condition expression.\n"} {"task_id": "always_if2", "description": "Fix any and all bugs in this code:\n\n// module top_module (\n// input cpu_overheated,\n// output reg shut_off_computer,\n// input arrived,\n// input gas_tank_empty,\n// output reg keep_driving ); //\n\n// always @(*) begin\n// if (cpu_overheated)\n// shut_off_computer = 1;\n// end\n\n// always @(*) begin\n// if (~arrived)\n// keep_driving = ~gas_tank_empty;\n// end\n\n// endmodule\n", "module_header": "module top_module (\n\tinput cpu_overheated,\n\toutput reg shut_off_computer,\n\tinput arrived,\n\tinput gas_tank_empty,\n\toutput reg keep_driving\n);\n", "original_code": "module top_module (\n\tinput cpu_overheated,\n\toutput reg shut_off_computer,\n\tinput arrived,\n\tinput gas_tank_empty,\n\toutput reg keep_driving\n);\n parameter cpu_overheated = 1'b0;\n parameter arrived = 1'b0;\n parameter gas_tank_empty = 1'b0;\n\n always @(cpu_overheated) begin\n if (cpu_overheated) begin\n shut_off_computer <= 1'b1;\n end else begin\n shut_off_computer <= 1'b0;\n end\n end\n\n always @(arrived or gas_tank_empty) begin\n if (~arrived) begin\n keep_driving <= ~gas_tank_empty;\n end else begin\n keep_driving <= 1'b0;\n end\n end\n\nendmodule", "error": "4: : It was declared here as a net.\n2: : It was declared here as a net.\n5: : It was declared here as a net.\n10: error: 'gas_tank_empty' has already been declared in this scope.\n8: error: 'cpu_overheated' has already been declared in this scope.\n9: error: 'arrived' has already been declared in this scope.\n"} {"task_id": "always_nolatches", "description": "Suppose you're building a circuit to process scancodes from a PS/2 keyboard for a game. Given the last two bytes of scancodes received, you need to indicate whether one of the arrow keys on the keyboard have been pressed. This involves a fairly simple mapping, which can be implemented as a case statement (or if-elseif) with four cases.\n// Scancode[15:0] | Arrow key\n// 16'he06b | left arrow\n// 16'he072 | down arrow\n// 16'he074 | right arrow\n// 16'he075 | up arrow\n// Anything else | none\n// Your circuit has one 16-bit input, and four outputs. Build this circuit that recognizes these four scancodes and asserts the correct output.\n\n", "module_header": "module top_module (\n\tinput [15:0] scancode,\n\toutput reg left,\n\toutput reg down,\n\toutput reg right,\n\toutput reg up\n);\n", "original_code": "module top_module (\n\tinput [15:0] scancode,\n\toutput reg left,\n\toutput reg down,\n\toutput reg right,\n\toutput reg up\n);\n always @(posedge clk) begin\n\t\tcase (scancode)\n\t\t\t16'h004B: left <= 1;\n\t\t\t16'h0050: down <= 1;\n\t\t\t16'h004D: right <= 1;\n\t\t\t16'h0052: up <= 1;\n\t\t\tdefault: begin\n\t\t\t\tleft <= 0;\n\t\t\t\tdown <= 0;\n\t\t\t\tright <= 0;\n\t\t\t\tup <= 0;\n\t\t\tend\n\t\tendcase\n end\nendmodule", "error": "8: error: Failed to evaluate event expression 'posedge clk'.\n8: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "andgate", "description": "Create a module that implements an AND gate.", "module_header": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n", "original_code": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n and_gate and_inst(\n .a(a),\n .b(b),\n .out(out)\n );\n\nendmodule", "error": "6: error: Unknown module type: and_gate\n"} {"task_id": "bugs_case", "description": "This combinational circuit is supposed to recognize 8-bit keyboard scancodes for keys 0 through 9. It should indicate whether one of the 10 cases were recognized (valid), and if so, which key was detected. If the 8-bit input is 8'h45, 8'h16, 8'h1e, 8'h26, 8'h25, 8'h2e, 8'h36, 8'h3d, 8'h3e, or 8'h46, the 4-bit output will be set to 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9 respectively, the 1-bit valid would be set to 1. If the input does not match any of the cases, both output signals would be set to 0.", "module_header": "module top_module (\n\tinput [7:0] code,\n\toutput reg [3:0] out,\n\toutput reg valid\n);\n", "original_code": "module top_module (\n\tinput [7:0] code,\n\toutput reg [3:0] out,\n\toutput reg valid\n);\n\n wire [7:0] code_i = code;\n wire [3:0] out_i = out;\n wire valid_i = valid;\n\n assign valid = valid_i;\n assign out = out_i;\n\n always @* begin\n case (code_i)\n 8'h45: out_i = 0;\n 8'h16: out_i = 1;\n 8'h1e: out_i = 2;\n 8'h26: out_i = 3;\n 8'h25: out_i = 4;\n 8'h2e: out_i = 5;\n 8'h36: out_i = 6;\n 8'h3d: out_i = 7;\n 8'h3e: out_i = 8;\n 8'h46: out_i = 9;\n default: begin\n out_i = 0;\n valid_i = 0;\n end\n endcase\n end\nendmodule", "error": "17: error: 'out_i' is not a valid l-value for a procedural assignment.\n19: error: 'out_i' is not a valid l-value for a procedural assignment.\n20: error: 'out_i' is not a valid l-value for a procedural assignment.\n22: error: 'out_i' is not a valid l-value for a procedural assignment.\n23: error: 'out_i' is not a valid l-value for a procedural assignment.\n24: error: 'out_i' is not a valid l-value for a procedural assignment.\n16: error: 'out_i' is not a valid l-value for a procedural assignment.\n9: : 'valid_i' is declared here as a wire.\n8: : 'out_i' is declared here as a wire.\n25: error: 'out_i' is not a valid l-value for a procedural assignment.\n18: error: 'out_i' is not a valid l-value for a procedural assignment.\n21: error: 'out_i' is not a valid l-value for a procedural assignment.\n27: error: 'out_i' is not a valid l-value for a procedural assignment.\n28: error: 'valid_i' is not a valid l-value for a procedural assignment.\n"} {"task_id": "bugs_mux2", "description": "Find the bug and fix this 8-bit wide 2-to-1 mux.\n\n// module top_module (\n// input sel,\n// input [7:0] a,\n// input [7:0] b,\n// output out );\n\n// assign out = (~sel & a) | (sel & b);\n\n// endmodule", "module_header": "module top_module (\n\tinput sel,\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput reg [7:0] out\n);\n", "original_code": "module top_module (\n\tinput sel,\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput reg [7:0] out\n);\n assign out = {out[0], out[1], out[2], out[3], out[4], out[5], out[6], out[7]} & {sel, sel, sel, sel, sel, sel, sel, sel};\n\n always @(*) begin\n\t\tif (sel == 1'b0)\n\t\t\tout = a;\n\t\telse\n\t\t\tout = b;\n end\n\nendmodule", "error": "13: error: Cannot perform procedural assignment to variable 'out' because it is also continuously assigned.\n11: error: Cannot perform procedural assignment to variable 'out' because it is also continuously assigned.\n"} {"task_id": "circuit1", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b q \n// 0ns 0 0 0 \n// 5ns 0 0 0 \n// 10ns 0 0 0 \n// 15ns 0 0 0 \n// 20ns 0 0 0 \n// 25ns 0 1 0 \n// 30ns 0 1 0 \n// 35ns 1 0 0 \n// 40ns 1 0 0 \n// 45ns 1 1 1 \n// 50ns 1 1 1 \n// 55ns 0 0 0 \n// 60ns 0 0 0 \n// 65ns 0 1 0 \n// 70ns 0 1 0 \n// 75ns 1 0 0 \n// 80ns 1 0 0 \n// 85ns 1 1 1 \n// 90ns 1 1 1 \n", "module_header": "module top_module (\n\tinput a, \n\tinput b, \n\toutput q\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b, \n\toutput q\n);\nalways @(*)\nbegin\n\tq = (a & b) | (a & ~b) | (~a & b);\nend\n\nendmodule\n", "error": "4: : 'q' is declared here as a wire.\n8: error: 'q' is not a valid l-value for a procedural assignment.\n"} {"task_id": "circuit10", "description": "This is a sequential circuit. The circuit consists of combinational logic and one bit of memory (i.e., one flip-flop). The output of the flip-flop has been made observable through the output state.\n\n// Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time clk a b state q \n// 0ns 0 1 x x x \n// 5ns 1 1 x x x \n// 10ns 0 0 0 x x \n// 15ns 1 0 0 0 0 \n// 20ns 0 0 0 0 0 \n// 25ns 1 0 0 0 0 \n// 30ns 0 0 0 0 0 \n// 35ns 1 0 0 0 0 \n// 40ns 0 0 0 0 0 \n// 45ns 1 0 1 0 1 \n// 50ns 0 0 1 0 1 \n// 55ns 1 1 0 0 1 \n// 60ns 0 1 0 0 1 \n// 65ns 1 1 1 0 0 \n// 70ns 0 1 1 0 0 \n// 75ns 1 0 0 1 1 \n// 80ns 0 0 0 1 1 \n// 85ns 1 1 1 0 0 \n// 90ns 0 1 1 0 0 \n// 95ns 1 1 1 1 1 \n// 100ns 0 1 1 1 1 \n// 105ns 1 1 1 1 1 \n// 110ns 0 1 1 1 1 \n// 115ns 1 1 0 1 0 \n// 120ns 0 1 0 1 0 \n// 125ns 1 0 1 1 0 \n// 130ns 0 0 1 1 0 \n// 135ns 1 0 0 1 1 \n// 140ns 0 0 0 1 1 \n// 145ns 1 0 0 0 0 \n// 150ns 0 0 0 0 0 \n// 155ns 1 0 0 0 0 \n// 160ns 0 0 0 0 0 \n// 165ns 1 0 0 0 0 \n// 170ns 0 0 0 0 0 \n// 175ns 1 0 0 0 0 \n// 180ns 0 0 0 0 0 \n// 185ns 1 0 0 0 0 \n// 190ns 0 0 0 0 0 ", "module_header": "module top_module (\n\tinput clk,\n\tinput a,\n\tinput b,\n\toutput q,\n\toutput state\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput a,\n\tinput b,\n\toutput q,\n\toutput state\n);\n assign state = (a) ? 1'b1 : ((b) ? 1'b1 : 1'b0);\n always @(posedge clk)\n q <= state;\n\nendmodule", "error": "10: error: 'q' is not a valid l-value for a procedural assignment.\n5: : 'q' is declared here as a wire.\n"} {"task_id": "circuit10", "description": "This is a sequential circuit. The circuit consists of combinational logic and one bit of memory (i.e., one flip-flop). The output of the flip-flop has been made observable through the output state.\n\n// Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time clk a b state q \n// 0ns 0 1 x x x \n// 5ns 1 1 x x x \n// 10ns 0 0 0 x x \n// 15ns 1 0 0 0 0 \n// 20ns 0 0 0 0 0 \n// 25ns 1 0 0 0 0 \n// 30ns 0 0 0 0 0 \n// 35ns 1 0 0 0 0 \n// 40ns 0 0 0 0 0 \n// 45ns 1 0 1 0 1 \n// 50ns 0 0 1 0 1 \n// 55ns 1 1 0 0 1 \n// 60ns 0 1 0 0 1 \n// 65ns 1 1 1 0 0 \n// 70ns 0 1 1 0 0 \n// 75ns 1 0 0 1 1 \n// 80ns 0 0 0 1 1 \n// 85ns 1 1 1 0 0 \n// 90ns 0 1 1 0 0 \n// 95ns 1 1 1 1 1 \n// 100ns 0 1 1 1 1 \n// 105ns 1 1 1 1 1 \n// 110ns 0 1 1 1 1 \n// 115ns 1 1 0 1 0 \n// 120ns 0 1 0 1 0 \n// 125ns 1 0 1 1 0 \n// 130ns 0 0 1 1 0 \n// 135ns 1 0 0 1 1 \n// 140ns 0 0 0 1 1 \n// 145ns 1 0 0 0 0 \n// 150ns 0 0 0 0 0 \n// 155ns 1 0 0 0 0 \n// 160ns 0 0 0 0 0 \n// 165ns 1 0 0 0 0 \n// 170ns 0 0 0 0 0 \n// 175ns 1 0 0 0 0 \n// 180ns 0 0 0 0 0 \n// 185ns 1 0 0 0 0 \n// 190ns 0 0 0 0 0 ", "module_header": "module top_module (\n\tinput clk,\n\tinput a,\n\tinput b,\n\toutput q,\n\toutput state\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput a,\n\tinput b,\n\toutput q,\n\toutput state\n);\n parameter [0:0] STATE_INIT = 1'b0;\n parameter [0:0] STATE_A = 1'b1;\n\n reg [0:0] state_reg;\n wire [0:0] state_next;\n\n assign state = state_reg;\n\n always @* begin\n state_next = state_reg;\n case (state_reg)\n STATE_INIT: begin\n if (a) begin\n state_next = STATE_A;\n end\n end\n STATE_A: begin\n if (!a) begin\n state_next = STATE_INIT;\n end\n end\n endcase\n end\n\n always @(posedge clk) begin\n state_reg <= state_next;\n end\n\n assign q = (state_reg == STATE_A) ? 1'b1 : 1'b0;\n\nendmodule", "error": "21: error: 'state_next' is not a valid l-value for a procedural assignment.\n12: : 'state_next' is declared here as a wire.\n26: error: 'state_next' is not a valid l-value for a procedural assignment.\n17: error: 'state_next' is not a valid l-value for a procedural assignment.\n"} {"task_id": "circuit3", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b c d q \n// 0ns 0 0 0 0 0 \n// 5ns 0 0 0 0 0 \n// 10ns 0 0 0 0 0 \n// 15ns 0 0 0 0 0 \n// 20ns 0 0 0 1 0 \n// 25ns 0 0 1 0 0 \n// 30ns 0 0 1 1 0 \n// 35ns 0 1 0 0 0 \n// 40ns 0 1 0 1 1 \n// 45ns 0 1 1 0 1 \n// 50ns 0 1 1 1 1 \n// 55ns 1 0 0 0 0 \n// 60ns 1 0 0 1 1 \n// 65ns 1 0 1 0 1 \n// 70ns 1 0 1 1 1 \n// 75ns 1 1 0 0 0 \n// 80ns 1 1 0 1 1 \n// 85ns 1 1 1 0 1 \n// 90ns 1 1 1 1 1 ", "module_header": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n reg q_reg;\n\n always @(posedge clk) begin\n if (c && !d) begin\n q_reg <= 0;\n end else if (!c && d) begin\n q_reg <= 1;\n end else if (c && d) begin\n q_reg <= a;\n end else begin\n q_reg <= b;\n end\n end\n\n assign q = q_reg;\n\nendmodule", "error": "10: error: Failed to evaluate event expression 'posedge clk'.\n10: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "circuit4", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b c d q \n// 0ns 0 0 0 0 0 \n// 5ns 0 0 0 0 0 \n// 10ns 0 0 0 0 0 \n// 15ns 0 0 0 0 0 \n// 20ns 0 0 0 1 0 \n// 25ns 0 0 1 0 1 \n// 30ns 0 0 1 1 1 \n// 35ns 0 1 0 0 1 \n// 40ns 0 1 0 1 1 \n// 45ns 0 1 1 0 1 \n// 50ns 0 1 1 1 1 \n// 55ns 1 0 0 0 0 \n// 60ns 1 0 0 1 0 \n// 65ns 1 0 1 0 1 \n// 70ns 1 0 1 1 1 \n// 75ns 1 1 0 0 1 \n// 80ns 1 1 0 1 1 \n// 85ns 1 1 1 0 1 \n// 90ns 1 1 1 1 1 ", "module_header": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n reg q_reg;\n always @(posedge clk) begin\n if (c && !d) begin\n q_reg <= 0;\n end else if (!c && d) begin\n q_reg <= 1;\n end else if (c && d) begin\n q_reg <= a;\n end else begin\n q_reg <= b;\n end\n end\n assign q = q_reg;\n\nendmodule", "error": "9: error: Failed to evaluate event expression 'posedge clk'.\n9: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "circuit4", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b c d q \n// 0ns 0 0 0 0 0 \n// 5ns 0 0 0 0 0 \n// 10ns 0 0 0 0 0 \n// 15ns 0 0 0 0 0 \n// 20ns 0 0 0 1 0 \n// 25ns 0 0 1 0 1 \n// 30ns 0 0 1 1 1 \n// 35ns 0 1 0 0 1 \n// 40ns 0 1 0 1 1 \n// 45ns 0 1 1 0 1 \n// 50ns 0 1 1 1 1 \n// 55ns 1 0 0 0 0 \n// 60ns 1 0 0 1 0 \n// 65ns 1 0 1 0 1 \n// 70ns 1 0 1 1 1 \n// 75ns 1 1 0 0 1 \n// 80ns 1 1 0 1 1 \n// 85ns 1 1 1 0 1 \n// 90ns 1 1 1 1 1 ", "module_header": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b, \n\tinput c, \n\tinput d,\n\toutput q\n);\n\n parameter logic [0:0] q_default = 1'b0;\n assign q = (a & b & ~c & d) | (~a & ~b & c & d) | (a & ~b & ~c & ~d) | (~a & b & c & ~d) | (a & b & c & d) | (~a & ~b & ~c & d) | (~a & b & ~c & ~d) | (a & ~b & c & ~d);\n initial begin\n q = q_default;\n end\n always @(a or b or c or d) begin\n q = (a & b & ~c & d) | (~a & ~b & c & d) | (a & ~b & ~c & ~d) | (~a & b & c & ~d) | (a & b & c & d) | (~a & ~b & ~c & d) | (~a & b & ~c & ~d) | (a & ~b & c & ~d);\n end\n\nendmodule", "error": "15: error: 'q' is not a valid l-value for a procedural assignment.\n12: error: 'q' is not a valid l-value for a procedural assignment.\n6: : 'q' is declared here as a wire.\n"} {"task_id": "circuit5", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b c d e q \n// 0ns x x x x x x \n// 5ns x x x x x x \n// 10ns x x x x x x \n// 15ns a b 0 d e b \n// 20ns a b 1 d e e \n// 25ns a b 2 d e a \n// 30ns a b 3 d e d \n// 35ns a b 4 d e f \n// 40ns a b 5 d e f \n// 45ns a b 6 d e f \n// 50ns a b 7 d e f \n// 55ns a b 8 d e f \n// 60ns a b 9 d e f \n// 65ns a b a d e f \n// 70ns a b b d e f \n// 75ns a b c d e f \n// 80ns a b d d e f \n// 85ns a b e d e f \n// 90ns a b f d e f ", "module_header": "module top_module (\n\tinput [3:0] a, \n\tinput [3:0] b, \n\tinput [3:0] c, \n\tinput [3:0] d,\n\tinput [3:0] e,\n\toutput reg [3:0] q\n);\n", "original_code": "module top_module (\n\tinput [3:0] a, \n\tinput [3:0] b, \n\tinput [3:0] c, \n\tinput [3:0] d,\n\tinput [3:0] e,\n\toutput reg [3:0] q\n);\n always @(*) begin\n case (d)\n 4'b0000: q = b;\n 4'b0001: q = e;\n 4'b0010: q = a;\n 4'b0011: q = d;\n 4'b0100: q = f;\n 4'b0101: q = f;\n 4'b0110: q = f;\n 4'b0111: q = f;\n 4'b1000: q = f;\n 4'b1001: q = f;\n 4'b1010: q = f;\n 4'b1011: q = f;\n 4'b1100: q = f;\n 4'b1101: q = f;\n 4'b1110: q = f;\n 4'b1111: q = f;\n endcase\n end\n\nendmodule", "error": "26: error: Unable to bind wire/reg/memory `f' in `top_module'\n21: error: Unable to bind wire/reg/memory `f' in `top_module'\n22: error: Unable to bind wire/reg/memory `f' in `top_module'\n16: error: Unable to bind wire/reg/memory `f' in `top_module'\n18: error: Unable to bind wire/reg/memory `f' in `top_module'\n23: error: Unable to bind wire/reg/memory `f' in `top_module'\n25: error: Unable to bind wire/reg/memory `f' in `top_module'\n24: error: Unable to bind wire/reg/memory `f' in `top_module'\n20: error: Unable to bind wire/reg/memory `f' in `top_module'\n17: error: Unable to bind wire/reg/memory `f' in `top_module'\n15: error: Unable to bind wire/reg/memory `f' in `top_module'\n19: error: Unable to bind wire/reg/memory `f' in `top_module'\n"} {"task_id": "circuit5", "description": "This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.\n\n// time a b c d e q \n// 0ns x x x x x x \n// 5ns x x x x x x \n// 10ns x x x x x x \n// 15ns a b 0 d e b \n// 20ns a b 1 d e e \n// 25ns a b 2 d e a \n// 30ns a b 3 d e d \n// 35ns a b 4 d e f \n// 40ns a b 5 d e f \n// 45ns a b 6 d e f \n// 50ns a b 7 d e f \n// 55ns a b 8 d e f \n// 60ns a b 9 d e f \n// 65ns a b a d e f \n// 70ns a b b d e f \n// 75ns a b c d e f \n// 80ns a b d d e f \n// 85ns a b e d e f \n// 90ns a b f d e f ", "module_header": "module top_module (\n\tinput [3:0] a, \n\tinput [3:0] b, \n\tinput [3:0] c, \n\tinput [3:0] d,\n\tinput [3:0] e,\n\toutput reg [3:0] q\n);\n", "original_code": "module top_module (\n\tinput [3:0] a, \n\tinput [3:0] b, \n\tinput [3:0] c, \n\tinput [3:0] d,\n\tinput [3:0] e,\n\toutput reg [3:0] q\n);\n always @(*) begin\n case ({a,b,c,d,e})\n 5'b00000: q = b;\n 5'b00001: q = e;\n 5'b00010: q = a;\n 5'b00011: q = d;\n 5'b00100: q = f;\n 5'b00101: q = f;\n 5'b00110: q = f;\n 5'b00111: q = f;\n 5'b01000: q = f;\n 5'b01001: q = f;\n 5'b01010: q = f;\n 5'b01011: q = f;\n 5'b01100: q = f;\n 5'b01101: q = f;\n 5'b01110: q = f;\n 5'b01111: q = f;\n 5'b10000: q = f;\n 5'b10001: q = f;\n 5'b10010: q = f;\n 5'b10011: q = f;\n 5'b10100: q = f;\n 5'b10101: q = f;\n 5'b10110: q = f;\n 5'b10111: q = f;\n 5'b11000: q = f;\n 5'b11001: q = f;\n 5'b11010: q = f;\n 5'b11011: q = f;\n 5'b11100: q = f;\n 5'b11101: q = f;\n 5'b11110: q = f;\n 5'b11111: q = f;\n default: q = f;\n endcase\n end\n\nendmodule", "error": "43: error: Unable to bind wire/reg/memory `f' in `top_module'\n41: error: Unable to bind wire/reg/memory `f' in `top_module'\n22: error: Unable to bind wire/reg/memory `f' in `top_module'\n16: error: Unable to bind wire/reg/memory `f' in `top_module'\n18: error: Unable to bind wire/reg/memory `f' in `top_module'\n40: error: Unable to bind wire/reg/memory `f' in `top_module'\n38: error: Unable to bind wire/reg/memory `f' in `top_module'\n21: error: Unable to bind wire/reg/memory `f' in `top_module'\n33: error: Unable to bind wire/reg/memory `f' in `top_module'\n23: error: Unable to bind wire/reg/memory `f' in `top_module'\n32: error: Unable to bind wire/reg/memory `f' in `top_module'\n25: error: Unable to bind wire/reg/memory `f' in `top_module'\n35: error: Unable to bind wire/reg/memory `f' in `top_module'\n15: error: Unable to bind wire/reg/memory `f' in `top_module'\n26: error: Unable to bind wire/reg/memory `f' in `top_module'\n28: error: Unable to bind wire/reg/memory `f' in `top_module'\n42: error: Unable to bind wire/reg/memory `f' in `top_module'\n24: error: Unable to bind wire/reg/memory `f' in `top_module'\n36: error: Unable to bind wire/reg/memory `f' in `top_module'\n17: error: Unable to bind wire/reg/memory `f' in `top_module'\n19: error: Unable to bind wire/reg/memory `f' in `top_module'\n27: error: Unable to bind wire/reg/memory `f' in `top_module'\n37: error: Unable to bind wire/reg/memory `f' in `top_module'\n29: error: Unable to bind wire/reg/memory `f' in `top_module'\n39: error: Unable to bind wire/reg/memory `f' in `top_module'\n30: error: Unable to bind wire/reg/memory `f' in `top_module'\n20: error: Unable to bind wire/reg/memory `f' in `top_module'\n34: error: Unable to bind wire/reg/memory `f' in `top_module'\n31: error: Unable to bind wire/reg/memory `f' in `top_module'\n"} {"task_id": "conwaylife", "description": "The \"game\" is played on a two-dimensional grid of cells, where each cell is either 1 (alive) or 0 (dead). At each time step, each cell changes state depending on how many neighbours it has:\n// (1) 0-1 neighbour: Cell becomes 0.\n// (2) 2 neighbours: Cell state does not change.\n// (3) 3 neighbours: Cell becomes 1.\n// (4) 4+ neighbours: Cell becomes 0.\n// The game is formulated for an infinite grid. In this circuit, we will use a 16x16 grid. To make things more interesting, we will use a 16x16 toroid, where the sides wrap around to the other side of the grid. For example, the corner cell (0,0) has 8 neighbours: (15,1), (15,0), (15,15), (0,1), (0,15), (1,1), (1,0), and (1,15). The 16x16 grid is represented by a length 256 vector, where each row of 16 cells is represented by a sub-vector: q[15:0] is row 0, q[31:16] is row 1, etc. \n// (1) load: Loads data into q at the next clock edge, for loading initial state. Active high synchronous.\n// (2) q: The 16x16 current state of the game, updated every clock cycle.\n// The game state should advance by one timestep every clock cycle.", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [255:0] data,\n\toutput reg [255:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [255:0] data,\n\toutput reg [255:0] q);\n reg [15:0] row;\n reg [15:0] col;\n reg [15:0] neighbours;\n reg [15:0] new_state;\n\n always @(posedge clk) begin\n if (load) begin\n q <= data;\n row <= 0;\n col <= 0;\n end else begin\n if (col == 15) begin\n col <= 0;\n row <= row + 1;\n end else begin\n col <= col + 1;\n end\n\n neighbours <= (q[row][col-1:0] + q[row][col+1:0] + q[(row-1)&15][col] + q[(row+1)&15][col] + q[(row-1)&15][col-1:0] + q[(row-1)&15][col+1:0] + q[(row+1)&15][col-1:0] + q[(row+1)&15][col+1:0]) % 2;\n\n if (neighbours == 2) begin\n new_state <= q[row][col];\n end else if (neighbours == 3) begin\n new_state <= 1;\n end else begin\n new_state <= 0;\n end\n\n q[row][col] <= new_state;\n end\n end\n\n always @(posedge clk) begin\n if (load) begin\n row <= 0;\n col <= 0;\n end else begin\n if (col == 15) begin\n col <= 0;\n row <= row + 1;\n end else begin\n col <= col + 1;\n end\n\n neighbours <= (q[row][col-1:0] + q[row][col+1:0] + q[(row-1)&15][col] + q[(row+1)&15][col] + q[(row-1)&15][col-1:0] + q[(row-1)&15][col+1:0] + q[(row+1)&15][col-1:0] + q[(row+1)&15][col+1:0]) % 2;\n\n if (neighbours == 2) begin\n new_state <= q[row][col];\n end else if (neighbours == 3) begin\n new_state <= 1;\n end else begin\n new_state <= 0;\n end\n\n q[row][col] <= new_state;\n end\n end\nendmodule", "error": "50: error: A reference to a net or variable (`row') is not allowed in a constant expression.\n50: error: A reference to a net or variable (`col') is not allowed in a constant expression.\n34: error: the number of indices (2) is greater than the number of dimensions (1).\n27: error: Array index expressions must be constant here.\n53: error: A reference to a net or variable (`row') is not allowed in a constant expression.\n24: error: A reference to a net or variable (`col') is not allowed in a constant expression.\n60: error: the number of indices (2) is greater than the number of dimensions (1).\n50: : The msb expression violates that rule: (col)+('sd1)\n53: error: Array index expressions must be constant here.\n24: error: A reference to a net or variable (`row') is not allowed in a constant expression.\n24: : The msb expression violates that rule: (col)-('sd1)\n50: error: Part select expressions must be constant integral values.\n24: error: Part select expressions must be constant integral values.\n24: : The msb expression violates that rule: (col)+('sd1)\n27: error: A reference to a net or variable (`row') is not allowed in a constant expression.\n50: : The msb expression violates that rule: (col)-('sd1)\n24: error: Array index expressions must be constant here.\n50: error: Array index expressions must be constant here.\n"} {"task_id": "conwaylife", "description": "The \"game\" is played on a two-dimensional grid of cells, where each cell is either 1 (alive) or 0 (dead). At each time step, each cell changes state depending on how many neighbours it has:\n// (1) 0-1 neighbour: Cell becomes 0.\n// (2) 2 neighbours: Cell state does not change.\n// (3) 3 neighbours: Cell becomes 1.\n// (4) 4+ neighbours: Cell becomes 0.\n// The game is formulated for an infinite grid. In this circuit, we will use a 16x16 grid. To make things more interesting, we will use a 16x16 toroid, where the sides wrap around to the other side of the grid. For example, the corner cell (0,0) has 8 neighbours: (15,1), (15,0), (15,15), (0,1), (0,15), (1,1), (1,0), and (1,15). The 16x16 grid is represented by a length 256 vector, where each row of 16 cells is represented by a sub-vector: q[15:0] is row 0, q[31:16] is row 1, etc. \n// (1) load: Loads data into q at the next clock edge, for loading initial state. Active high synchronous.\n// (2) q: The 16x16 current state of the game, updated every clock cycle.\n// The game state should advance by one timestep every clock cycle.", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [255:0] data,\n\toutput reg [255:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [255:0] data,\n\toutput reg [255:0] q);\n reg [255:0] q_next;\n reg [255:0] neighbours;\n reg [7:0] x, y;\n integer i, j, k, l;\n\n always @ (posedge clk) begin\n if (load) begin\n q <= data;\n end else begin\n q_next <= q;\n for (i = 0; i < 256; i = i + 1) begin\n x = i % 16;\n y = i / 16;\n neighbours = 0;\n for (k = -1; k <= 1; k = k + 1) begin\n for (l = -1; l <= 1; l = l + 1) begin\n if (k == 0 && l == 0) begin\n continue;\n end else begin\n j = (y + k + 16) % 16;\n j = (x + l + 16) % 16;\n neighbours = neighbours | (q[j + 16 * j] << (k + 1) * 4 + (l + 1) * 4);\n end\n end\n end\n if (neighbours[0:1] == 0 || neighbours[0:1] == 2 || neighbours[0:1] == 4) begin\n q_next[i] = 0;\n end else if (neighbours[0:1] == 1 || neighbours[0:1] == 3 || neighbours[0:1] == 5) begin\n q_next[i] = 1;\n end\n end\n q <= q_next;\n end\n end\n endmodule", "error": "33: error: part select neighbours[0:1] is out of order.\n31: error: part select neighbours[0:1] is out of order.\n"} {"task_id": "count15", "description": "Build a 4-bit binary counter that counts from 0 through 15, inclusive, with a period of 16. The reset input is active high synchronous, and should reset the counter to 0.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [3:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [3:0] q);\n counter counter_inst(\n .clk(clk),\n .reset(reset),\n .q(q));\n\nendmodule", "error": "5: error: Unknown module type: counter\n"} {"task_id": "count1to10", "description": "Make a decade counter that counts 1 through 10, inclusive. The reset input is active high synchronous, and should reset the counter to 1.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [3:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [3:0] q);\n\n always @(posedge clk) begin\n if (reset) begin\n q <= 4'b0001;\n end else if (q == 4'b1010) begin\n q <= 4'b0001;\n end else begin\n q <= q + 1;\n end\n end\n\n assign q_out = q;\n\n endmodule", "error": "16: warning: implicit definition of wire 'q_out'.\n"} {"task_id": "count_clock", "description": "Create a set of counters suitable for use as a 12-hour clock (with am/pm indicator). Your counters are clocked by a fast-running clk, with a pulse on ena whenever your clock should increment (i.e., once per second, while \"clk\" is much faster than once per second). The signal \"pm\" is asserted if the clock is PM, or is otherwise AM. hh, mm, and ss are two BCD (Binary-Coded Decimal) digits each for hours (01-12), minutes (00-59), and seconds (00-59). Reset is the active high synchronous signal that resets the clock to \"12:00 AM.\" Reset has higher priority than enable and can occur even when not enabled.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput ena,\n\toutput reg pm,\n\toutput reg [7:0] hh,\n\toutput reg [7:0] mm,\n\toutput reg [7:0] ss);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput ena,\n\toutput reg pm,\n\toutput reg [7:0] hh,\n\toutput reg [7:0] mm,\n\toutput reg [7:0] ss);\n reg [5:0] counter;\n reg [5:0] counter_100;\n reg [5:0] counter_1000;\n\n always @(posedge clk) begin\n if (reset) begin\n counter <= 6'd0;\n counter_100 <= 6'd0;\n counter_1000 <= 6'd0;\n pm <= 1'b0;\n hh <= 8'd12;\n mm <= 8'd0;\n ss <= 8'd0;\n end\n else if (ena) begin\n counter <= counter + 6'd1;\n if (counter == 6'd99) begin\n counter <= 6'd0;\n counter_100 <= counter_100 + 6'd1;\n end\n if (counter_100 == 6'd99) begin\n counter_100 <= 6'd0;\n counter_1000 <= counter_1000 + 6'd1;\n end\n if (counter_1000 == 6'd5) begin\n counter_1000 <= 6'd0;\n if (pm) begin\n if (hh == 8'd12) begin\n hh <= 8'd1;\n end\n else begin\n hh <= hh + 8'd1;\n end\n pm <= 1'b0;\n end\n else begin\n if (hh == 8'd12) begin\n hh <= 8'd1;\n pm <= 1'b1;\n end\n else begin\n hh <= hh + 8'd1;\n end\n end\n end\n if (ss == 8'd59) begin\n ss <= 8'd0;\n if (mm == 8'd59) begin\n mm <= 8'd0;\n end\n else begin\n mm <= mm + 8'd1;\n end\n end\n else begin\n ss <= ss + 8'd1;\n end\n end\n end\n endmodule", "error": "29: warning: Numeric constant truncated to 6 bits.\n25: warning: Numeric constant truncated to 6 bits.\n"} {"task_id": "count_clock", "description": "Create a set of counters suitable for use as a 12-hour clock (with am/pm indicator). Your counters are clocked by a fast-running clk, with a pulse on ena whenever your clock should increment (i.e., once per second, while \"clk\" is much faster than once per second). The signal \"pm\" is asserted if the clock is PM, or is otherwise AM. hh, mm, and ss are two BCD (Binary-Coded Decimal) digits each for hours (01-12), minutes (00-59), and seconds (00-59). Reset is the active high synchronous signal that resets the clock to \"12:00 AM.\" Reset has higher priority than enable and can occur even when not enabled.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput ena,\n\toutput reg pm,\n\toutput reg [7:0] hh,\n\toutput reg [7:0] mm,\n\toutput reg [7:0] ss);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput ena,\n\toutput reg pm,\n\toutput reg [7:0] hh,\n\toutput reg [7:0] mm,\n\toutput reg [7:0] ss);\n\n reg [5:0] count_ss;\n reg [5:0] count_mm;\n reg [4:0] count_hh;\n reg [1:0] count_pm;\n\n always @(posedge clk) begin\n if (reset) begin\n count_ss <= 0;\n count_mm <= 0;\n count_hh <= 0;\n count_pm <= 0;\n pm <= 0;\n hh <= 8'b00001010; // 10 in BCD\n mm <= 8'b00000000; // 00 in BCD\n ss <= 8'b00000000; // 00 in BCD\n end else if (ena) begin\n if (count_ss == 59) begin\n count_ss <= 0;\n if (count_mm == 59) begin\n count_mm <= 0;\n if (count_hh == 11) begin\n count_hh <= 0;\n count_pm <= 1;\n end else begin\n count_hh <= count_hh + 1;\n count_pm <= 0;\n end\n end else begin\n count_mm <= count_mm + 1;\n end\n end else begin\n count_ss <= count_ss + 1;\n end\n pm <= count_pm;\n hh <= (count_hh == 0) ? 8'b00001010 : // 10 in BCD\n (count_hh == 1) ? 8'b00001100 : // 12 in BCD\n (count_hh == 2) ? 8'b00001101 : // 13 in BCD\n (count_hh == 3) ? 8'b00001110 : // 14 in BCD\n (count_hh == 4) ? 8'b00001111 : // 15 in BCD\n (count_hh == 5) ? 8'b00010000 : // 16 in BCD\n (count_hh == 6) ? 8'b00010001 : // 17 in BCD\n (count_hh == 7) ? 8'b00010010 : // 18 in BCD\n (count_hh == 8) ? 8'b00010011 : // 19 in BCD\n (count_hh == 9) ? 8'b00010100 : // 20 in BCD\n (count_hh == 10) ? 8'b00010101 : // 21 in BCD\n (count_hh == 11) ? 8'b00010110 : // 22 in BCD\n 8'b00000000; // 00 in BCD\n mm <= (count_mm < 10) ? {1'b0, count_mm} : // 00-09 in BCD\n (count_mm < 20) ? {1'b1, count_mm - 10} : // 10-19 in BCD\n (count_mm < 30) ? {1'b1, count_mm - 20} : // 20-29 in BCD\n (count_mm < 40) ? {1'b1, count_mm - 30} : // 30-39 in BCD\n (count_mm < 50) ? {1'b1, count_mm - 40} : // 40-49 in BCD\n (count_mm < 59) ? {1'b1, count_mm - 50} : // 50-59 in BCD\n 8'b00000000; // 00 in BCD\n ss <= (count_ss < 10) ? {1'b0, count_ss} : // 00-09 in BCD\n (count_ss < 20) ? {1'b1, count_ss - 10} : // 10-19 in BCD\n (count_ss < 30) ? {1'b1, count_ss - 20} : // 20-29 in BCD\n (count_ss < 40) ? {1'b1, count_ss - 30} : // 30-39 in BCD\n (count_ss < 50) ? {1'b1, count_ss - 40} : // 40-49 in BCD\n (count_ss < 59) ? {1'b1, count_ss - 50} : // 50-59 in BCD\n 8'b00000000; // 00 in BCD\n end\n end\n endmodule", "error": "65: error: Concatenation operand \"(count_ss)-('sd10)\" has indefinite width.\n58: error: Concatenation operand \"(count_mm)-('sd10)\" has indefinite width.\n"} {"task_id": "countbcd", "description": "Build a 4-digit BCD (binary-coded decimal) counter. Each decimal digit is encoded using 4 bits: q[3:0] is the ones digit, q[7:4] is the tens digit, etc. For digits [3:1], also output an enable signal indicating when each of the upper three digits should be incremented. Include a synchronous active-high reset.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput [3:1] ena,\n\toutput reg [15:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput [3:1] ena,\n\toutput reg [15:0] q);\n // Internal registers for holding intermediate values of the counter\n reg [3:0] ones;\n reg [3:0] tens;\n reg [3:0] hundreds;\n reg [3:0] thousands;\n\n // Counter increment logic\n always @(posedge clk) begin\n if (reset) begin\n ones <= 4'b0000;\n tens <= 4'b0000;\n hundreds <= 4'b0000;\n thousands <= 4'b0000;\n end else begin\n if (ones == 4'b1001) begin\n ones <= 4'b0000;\n ena[1] <= 1;\n end else begin\n ones <= ones + 1;\n ena[1] <= 0;\n end\n\n if (tens == 4'b1001) begin\n tens <= 4'b0000;\n ena[2] <= 1;\n end else begin\n tens <= tens + 1;\n ena[2] <= 0;\n end\n\n if (hundreds == 4'b1001) begin\n hundreds <= 4'b0000;\n ena[3] <= 1;\n end else begin\n hundreds <= hundreds + 1;\n ena[3] <= 0;\n end\n\n if (thousands == 4'b1001) begin\n thousands <= 4'b0000;\n end else begin\n thousands <= thousands + 1;\n end\n end\n end\n\n // Output register for storing the BCD counter value\n always @(posedge clk) begin\n if (reset) begin\n q <= 16'b0000000000000000;\n end else begin\n q <= {thousands, hundreds, tens, ones};\n end\n end\n\n endmodule", "error": "30: error: 'ena['sd2]' is not a valid l-value for a procedural assignment.\n4: : 'ena['sd1]' is declared here as a wire.\n41: error: 'ena['sd3]' is not a valid l-value for a procedural assignment.\n22: error: 'ena['sd1]' is not a valid l-value for a procedural assignment.\n4: : 'ena['sd2]' is declared here as a wire.\n4: : 'ena['sd3]' is declared here as a wire.\n25: error: 'ena['sd1]' is not a valid l-value for a procedural assignment.\n38: error: 'ena['sd3]' is not a valid l-value for a procedural assignment.\n33: error: 'ena['sd2]' is not a valid l-value for a procedural assignment.\n"} {"task_id": "countbcd", "description": "Build a 4-digit BCD (binary-coded decimal) counter. Each decimal digit is encoded using 4 bits: q[3:0] is the ones digit, q[7:4] is the tens digit, etc. For digits [3:1], also output an enable signal indicating when each of the upper three digits should be incremented. Include a synchronous active-high reset.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput [3:1] ena,\n\toutput reg [15:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput [3:1] ena,\n\toutput reg [15:0] q);\n always @(posedge clk) begin\n if (reset) begin\n q <= 16'b0;\n ena <= 3'b0;\n end else begin\n q <= q + 1;\n if (q[15:12] == 4'b1001) begin\n ena <= 3'b1;\n end else begin\n ena <= 3'b0;\n end\n end\n end\n endmodule", "error": "15: error: 'ena' is not a valid l-value for a procedural assignment.\n4: : 'ena' is declared here as a wire.\n9: error: 'ena' is not a valid l-value for a procedural assignment.\n13: error: 'ena' is not a valid l-value for a procedural assignment.\n"} {"task_id": "counter_2bc", "description": "Build a two-bit saturating counter. The counter increments (up to a maximum of 3) when train_valid = 1 and train_taken = 1. It decrements (down to a minimum of 0) when train_valid = 1 and train_taken = 0. When not training (train_valid = 0), the counter keeps its value unchanged. areset is a positive edge triggered asynchronous reset that resets the counter to weakly not-taken (2'b01). Output state[1:0] is the two-bit counter value.", "module_header": "module top_module(\n input clk,\n input areset,\n input train_valid,\n input train_taken,\n output logic [1:0] state\n);\n", "original_code": "module top_module(\n input clk,\n input areset,\n input train_valid,\n input train_taken,\n output logic [1:0] state\n);\n always @ (posedge clk) begin\n if (areset) begin\n state <= 2'b01;\n end else if (train_valid == 1) begin\n if (train_taken == 1) begin\n state <= (state == 2'b11) ? 2'b11 : state + 1;\n end else begin\n state <= (state == 2'b00) ? 2'b00 : state - 1;\n end\n end\n end\n\n // If training is valid and not taken, counter cannot go below 0\n assign state = (train_valid == 1 && train_taken == 0 && state == 2'b00) ? 2'b00 : state;\n\n // If training is valid and taken, counter cannot go above 3\n assign state = (train_valid == 1 && train_taken == 1 && state == 2'b11) ? 2'b11 : state;\n\nendmodule", "error": "24: error: Variable 'state' cannot have multiple drivers.\n13: error: Cannot perform procedural assignment to variable 'state' because it is also continuously assigned.\n15: error: Cannot perform procedural assignment to variable 'state' because it is also continuously assigned.\n10: error: Cannot perform procedural assignment to variable 'state' because it is also continuously assigned.\n"} {"task_id": "counter_2bc", "description": "Build a two-bit saturating counter. The counter increments (up to a maximum of 3) when train_valid = 1 and train_taken = 1. It decrements (down to a minimum of 0) when train_valid = 1 and train_taken = 0. When not training (train_valid = 0), the counter keeps its value unchanged. areset is a positive edge triggered asynchronous reset that resets the counter to weakly not-taken (2'b01). Output state[1:0] is the two-bit counter value.", "module_header": "module top_module(\n input clk,\n input areset,\n input train_valid,\n input train_taken,\n output logic [1:0] state\n);\n", "original_code": "module top_module(\n input clk,\n input areset,\n input train_valid,\n input train_taken,\n output logic [1:0] state\n);\n sat_counter #( .AWIDTH(2) ) sat_cntr( .clk(clk), .areset(areset), .train_valid(train_valid), .train_taken(train_taken), .state(state) );\n\nendmodule", "error": "8: error: Unknown module type: sat_counter\n"} {"task_id": "countslow", "description": "Build a decade counter that counts from 0 through 9, inclusive, with a period of 10. The reset input is active high synchronous, and should reset the counter to 0. We want to be able to pause the counter rather than always incrementing every clock cycle, so the \"slowena\" input if high indicates when the counter should increment. ", "module_header": "module top_module(\n\tinput clk,\n\tinput slowena,\n\tinput reset,\n\toutput reg [3:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput slowena,\n\tinput reset,\n\toutput reg [3:0] q);\n always @(posedge clk) begin\n if (reset) begin\n q <= 4'b0000;\n end\n else if (slowena) begin\n q <= q + 1;\n end\n end\n\n assign q = q;\n\n always @(posedge clk) begin\n if (reset) begin\n q <= 4'b0000;\n end\n else if (slowena) begin\n q <= q + 1;\n end\n end\n\nendmodule", "error": "8: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n11: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n22: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n19: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n"} {"task_id": "countslow", "description": "Build a decade counter that counts from 0 through 9, inclusive, with a period of 10. The reset input is active high synchronous, and should reset the counter to 0. We want to be able to pause the counter rather than always incrementing every clock cycle, so the \"slowena\" input if high indicates when the counter should increment. ", "module_header": "module top_module(\n\tinput clk,\n\tinput slowena,\n\tinput reset,\n\toutput reg [3:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput slowena,\n\tinput reset,\n\toutput reg [3:0] q);\n reg [4:0] counter = 0;\n reg [3:0] next_q;\n\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n counter <= 0;\n end\n else if (slowena) begin\n counter <= counter + 1;\n end\n end\n\n always @(counter) begin\n case(counter)\n 0: next_q = 4'b0000;\n 1: next_q = 4'b0001;\n 2: next_q = 4'b0010;\n 3: next_q = 4'b0011;\n 4: next_q = 4'b0100;\n 5: next_q = 4'b0101;\n 6: next_q = 4'b0110;\n 7: next_q = 4'b0111;\n 8: next_q = 4'b1000;\n 9: next_q = 4'b1001;\n default: next_q = 4'b0000;\n endcase\n end\n\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n q <= 0;\n end\n else if (slowena) begin\n q <= next_q;\n end\n end\n\n // Output a pulse every time the counter increments\n reg pulse = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n pulse <= 0;\n end\n else if (counter > 0) begin\n pulse <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 2\n reg mult2 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult2 <= 0;\n end\n else if (counter % 2 == 0) begin\n mult2 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 3\n reg mult3 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult3 <= 0;\n end\n else if (counter % 3 == 0) begin\n mult3 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 4\n reg mult4 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult4 <= 0;\n end\n else if (counter % 4 == 0) begin\n mult4 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 5\n reg mult5 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult5 <= 0;\n end\n else if (counter % 5 == 0) begin\n mult5 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 6\n reg mult6 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult6 <= 0;\n end\n else if (counter % 6 == 0) begin\n mult6 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 7\n reg mult7 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult7 <= 0;\n end\n else if (counter % 7 == 0) begin\n mult7 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 8\n reg mult8 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult8 <= 0;\n end\n else if (counter % 8 == 0) begin\n mult8 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 9\n reg mult9 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult9 <= 0;\n end\n else if (counter % 9 == 0) begin\n mult9 <= 1;\n end\n end\n\n // Output a 1 when the counter is at a multiple of 10\n reg mult10 = 0;\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n mult10 <= 0;\n end\n else if (counter % 10 == 0) begin\n mult10 <= 1;\n end\n end\n\n // Output all of the multiples\n assign pulse_out = pulse;\n assign mult2_out = mult2;\n assign mult3_out = mult3;\n assign mult4_out = mult4;\n assign mult5_out = mult5;\n assign mult6_out = mult6;\n assign mult7_out = mult7;\n assign mult8_out = mult8;\n assign mult9_out = mult9;\n assign mult10_out = mult10;\n\n // Output the current counter value\n assign out = counter;\n\n // Output a 1 when the counter is at 9\n assign end_out = (counter == 9);\n\n // Output a 1 when the counter is at 0\n assign begin_out = (counter == 0);\n\n // Output a 1 when the pulse is active\n assign pulse_out = pulse;\n\n // Output a 1 when the counter is at a multiple of 10\n assign mult10_out = (counter % 10 == 0);\n\n // Output a 1 when the counter is at a multiple of 9\n assign mult9_out = (counter % 9 == 0);\n\n // Output a 1 when the counter is at a multiple of 8\n assign mult8_out = (counter % 8 == 0);\n\n // Output a 1 when the counter is at a multiple of 7\n assign mult7_out = (counter % 7 == 0);\n\n // Output a 1 when the counter is at a multiple of 6\n assign mult6_out = (counter % 6 == 0);\n\n // Output a 1 when the counter is at a multiple of 5\n assign mult5_out = (counter % 5 == 0);\n\n // Output a 1 when the counter is at a multiple of 4\n assign mult4_out = (counter % 4 == 0);\n\n // Output a 1 when the counter is at a multiple of 3\n assign mult3_out = (counter % 3 == 0);\n\n // Output a 1 when the counter is at a multiple of 2\n assign mult2_out = (counter % 2 == 0);\n\n // Output a 1 when the counter is at 9\n assign end_out = (counter == 9);\n\n // Output a 1 when the counter is at 0\n assign begin_out = (counter == 0);\n endmodule", "error": "161: warning: implicit definition of wire 'mult8_out'.\n172: warning: implicit definition of wire 'begin_out'.\n154: warning: implicit definition of wire 'pulse_out'.\n155: warning: implicit definition of wire 'mult2_out'.\n157: warning: implicit definition of wire 'mult4_out'.\n163: warning: implicit definition of wire 'mult10_out'.\n158: warning: implicit definition of wire 'mult5_out'.\n156: warning: implicit definition of wire 'mult3_out'.\n162: warning: implicit definition of wire 'mult9_out'.\n166: warning: implicit definition of wire 'out'.\n160: warning: implicit definition of wire 'mult7_out'.\n169: warning: implicit definition of wire 'end_out'.\n159: warning: implicit definition of wire 'mult6_out'.\n"} {"task_id": "dff", "description": "Create a single D flip-flop.", "module_header": "module top_module(\n\tinput clk,\n\tinput d,\n\toutput reg q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput d,\n\toutput reg q);\n clock_divider clk_div(\n .clk(clk),\n .clk_out(clk_out)\n );\n\n always @(posedge clk_out) begin\n q <= d;\n end\n\n\tendmodule", "error": "5: error: Unknown module type: clock_divider\n7: warning: implicit definition of wire 'clk_out'.\n"} {"task_id": "dff", "description": "Create a single D flip-flop.", "module_header": "module top_module(\n\tinput clk,\n\tinput d,\n\toutput reg q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput d,\n\toutput reg q);\n\n reg q_next;\n\n always @(posedge clk) begin\n q_next <= d;\n end\n\n // Asynchronous load\n always @(d) begin\n q <= d;\n end\n\n // Output\n assign q = q_next;\n\n endmodule", "error": "14: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n"} {"task_id": "dff16e", "description": "Create 16 D flip-flops. It's sometimes useful to only modify parts of a group of flip-flops. The byte-enable inputs control whether each byte of the 16 registers should be written to on that cycle. byteena[1] controls the upper byte d[15:8], while byteena[0] controls the lower byte d[7:0]. resetn is a synchronous, active-low reset. All DFFs should be triggered by the positive edge of clk.", "module_header": "module top_module(\n\tinput clk,\n\tinput resetn,\n\tinput [1:0] byteena,\n\tinput [15:0] d,\n\toutput reg [15:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput resetn,\n\tinput [1:0] byteena,\n\tinput [15:0] d,\n\toutput reg [15:0] q);\n reg [15:0] ff [0:15];\n\n always @(posedge clk) begin\n if (!resetn) begin\n for (i=0; i<16; i=i+1) begin\n ff[i] <= 16'b0;\n end\n end else begin\n for (i=0; i<16; i=i+1) begin\n if (byteena[1]) begin\n if (i<8) begin\n ff[i] <= d[15:8];\n end else begin\n ff[i] <= ff[i];\n end\n end else begin\n if (i<8) begin\n ff[i] <= d[7:0];\n end else begin\n ff[i] <= ff[i];\n end\n end\n end\n end\n end\n\n always @(posedge clk) begin\n if (!resetn) begin\n q <= 16'b0;\n end else begin\n q <= {ff[15], ff[14], ff[13], ff[12], ff[11], ff[10], ff[9], ff[8], ff[7], ff[6], ff[5], ff[4], ff[3], ff[2], ff[1], ff[0]};\n end\n end\n\n endmodule", "error": "11: register ``i'' unknown in top_module.\n15: register ``i'' unknown in top_module.\n"} {"task_id": "dff8ar", "description": "Create 8 D flip-flops with active high asynchronous reset. The output should be reset to 0. All DFFs should be triggered by the positive edge of clk.", "module_header": "module top_module(\n\tinput clk,\n\tinput [7:0] d,\n\tinput areset,\n\toutput reg [7:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput [7:0] d,\n\tinput areset,\n\toutput reg [7:0] q);\n reg [7:0] ff [0:7];\n\n always @(posedge clk or negedge areset) begin\n if(areset) begin\n q <= 8'b0;\n ff <= 8'b0;\n end else begin\n q <= ff[0];\n ff[0] <= d;\n ff[1] <= ff[0];\n ff[2] <= ff[1];\n ff[3] <= ff[2];\n ff[4] <= ff[3];\n ff[5] <= ff[4];\n ff[6] <= ff[5];\n ff[7] <= ff[6];\n end\n end\n endmodule", "error": "11: error: The expression '8'd0' cannot be implicitly cast to the target type.\n"} {"task_id": "ece241_2013_q12", "description": "In this question, you will design a circuit for an 8x1 memory, where writing to the memory is accomplished by shifting-in bits, and reading is \"random access\", as in a typical RAM. You will then use the circuit to realize a 3-input logic function. First, create an 8-bit shift register with 8 D-type flip-flops. Label the flip-flop outputs from Q[0]...Q[7]. The shift register input should be called S, which feeds the input of Q[0] (MSB is shifted in first). The enable input is synchronous active high and controls whether to shift. Extend the circuit to have 3 additional inputs A,B,C and an output Z. The circuit's behaviour should be as follows: when ABC is 000, Z=Q[0], when ABC is 001, Z=Q[1], and so on. Your circuit should contain ONLY the 8-bit shift register, and multiplexers. ", "module_header": "module top_module (\n\tinput clk,\n\tinput enable,\n\tinput S,\n\tinput A,\n\tinput B,\n\tinput C,\n\toutput reg Z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput enable,\n\tinput S,\n\tinput A,\n\tinput B,\n\tinput C,\n\toutput reg Z\n);\nreg [7:0] Q;\n\treg [2:0] addr;\n\n\talways @(posedge clk) begin\n\t\tif (enable) begin\n\t\t\tQ <= {Q[6:0], S};\n\t\tend\n\tend\n\n\talways @(*) begin\n\t\tcase ({A,B,C})\n\t\t\t3'b000: addr = 3'b000;\n\t\t\t3'b001: addr = 3'b001;\n\t\t\t3'b010: addr = 3'b010;\n\t\t\t3'b011: addr = 3'b011;\n\t\t\t3'b100: addr = 3'b100;\n\t\t\t3'b101: addr = 3'b101;\n\t\t\t3'b110: addr = 3'b110;\n\t\t\t3'b111: addr = 3'b111;\n\t\tendcase\n\tend\n\n\tassign Z = addr[0] ? Q[7] : addr[1] ? Q[6] : addr[2] ? Q[5] : addr[3] ? Q[4] : addr[4] ? Q[3] : addr[5] ? Q[2] : addr[6] ? Q[1] : Q[0];\n\nendmodule\n", "error": "32: warning: Constant bit select [3] is after vector addr[2:0].\n32: : Replacing select with a constant 1'bx.\n32: warning: Constant bit select [5] is after vector addr[2:0].\n32: warning: Constant bit select [6] is after vector addr[2:0].\n32: warning: Constant bit select [4] is after vector addr[2:0].\n"} {"task_id": "ece241_2013_q2", "description": "A single-output digital system with four inputs (a,b,c,d) generates a logic-1 when 2, 7, or 15 appears on the inputs, and a logic-0 when 0, 1, 4, 5, 6, 9, 10, 13, or 14 appears. The input conditions for the numbers 3, 8, 11, and 12 never occur in this system. For example, 7 corresponds to a,b,c,d being set to 0,1,1,1, respectively. Determine the output out_sop in minimum sum-of-products form, and the output out_pos in minimum product-of-sums form.\n\n", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out_sop,\n\toutput out_pos\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out_sop,\n\toutput out_pos\n);\n\n // Define the output signals\n wire out_sop;\n wire out_pos;\n\n // Define the intermediate signals\n wire abcd_0;\n wire abcd_1;\n wire abcd_2;\n wire abcd_3;\n wire abcd_4;\n wire abcd_5;\n wire abcd_6;\n wire abcd_7;\n wire abcd_8;\n wire abcd_9;\n wire abcd_10;\n wire abcd_11;\n wire abcd_12;\n wire abcd_13;\n wire abcd_14;\n wire abcd_15;\n\n // Define the logic for the intermediate signals\n assign abcd_0 = ~(a & b & c & d);\n assign abcd_1 = ~(a & b & c & ~d);\n assign abcd_2 = ~(a & b & ~c & d);\n assign abcd_3 = ~(a & b & ~c & ~d);\n assign abcd_4 = ~(a & ~b & c & d);\n assign abcd_5 = ~(a & ~b & c & ~d);\n assign abcd_6 = ~(a & ~b & ~c & d);\n assign abcd_7 = ~(a & ~b & ~c & ~d);\n assign abcd_8 = ~(~a & b & c & d);\n assign abcd_9 = ~(~a & b & c & ~d);\n assign abcd_10 = ~(~a & b & ~c & d);\n assign abcd_11 = ~(~a & b & ~c & ~d);\n assign abcd_12 = ~(~a & ~b & c & d);\n assign abcd_13 = ~(~a & ~b & c & ~d);\n assign abcd_14 = ~(~a & ~b & ~c & d);\n assign abcd_15 = ~(~a & ~b & ~c & ~d);\n\n // Define the logic for the output signals\n assign out_sop = abcd_0 | abcd_1 | abcd_2 | abcd_3 | abcd_4 | abcd_5 | abcd_6 | abcd_7 | abcd_8 | abcd_9 | abcd_10 | abcd_11 | abcd_12 | abcd_13 | abcd_14 | abcd_15;\n assign out_pos = ~(abcd_0 & abcd_1 & abcd_2 & abcd_3 & abcd_4 & abcd_5 & abcd_6 & abcd_7 & abcd_8 & abcd_9 & abcd_10 & abcd_11 & abcd_12 & abcd_13 & abcd_14 & abcd_15);\n\nendmodule", "error": "6: : It was declared here as a net.\n12: error: 'out_pos' has already been declared in this scope.\n7: : It was declared here as a net.\n11: error: 'out_sop' has already been declared in this scope.\n"} {"task_id": "ece241_2013_q2", "description": "A single-output digital system with four inputs (a,b,c,d) generates a logic-1 when 2, 7, or 15 appears on the inputs, and a logic-0 when 0, 1, 4, 5, 6, 9, 10, 13, or 14 appears. The input conditions for the numbers 3, 8, 11, and 12 never occur in this system. For example, 7 corresponds to a,b,c,d being set to 0,1,1,1, respectively. Determine the output out_sop in minimum sum-of-products form, and the output out_pos in minimum product-of-sums form.\n\n", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out_sop,\n\toutput out_pos\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out_sop,\n\toutput out_pos\n);\n\n // Define the output signals\n wire out_sop;\n wire out_pos;\n\n // Define the intermediate signals\n wire abcd_0;\n wire abcd_1;\n wire abcd_2;\n wire abcd_3;\n wire abcd_4;\n wire abcd_5;\n wire abcd_6;\n wire abcd_7;\n wire abcd_8;\n wire abcd_9;\n wire abcd_10;\n wire abcd_11;\n wire abcd_12;\n wire abcd_13;\n wire abcd_14;\n\n // Define the logic for the intermediate signals\n assign abcd_0 = ~(a & b & c & d);\n assign abcd_1 = ~(a & b & c & ~d);\n assign abcd_2 = ~(a & b & ~c & d);\n assign abcd_3 = ~(a & b & ~c & ~d);\n assign abcd_4 = ~(a & ~b & c & d);\n assign abcd_5 = ~(a & ~b & c & ~d);\n assign abcd_6 = ~(a & ~b & ~c & d);\n assign abcd_7 = ~(a & ~b & ~c & ~d);\n assign abcd_8 = ~(~a & b & c & d);\n assign abcd_9 = ~(~a & b & c & ~d);\n assign abcd_10 = ~(~a & b & ~c & d);\n assign abcd_11 = ~(~a & b & ~c & ~d);\n assign abcd_12 = ~(~a & ~b & c & d);\n assign abcd_13 = ~(~a & ~b & c & ~d);\n assign abcd_14 = ~(~a & ~b & ~c & d);\n\n // Define the logic for the output signals\n assign out_sop = abcd_0 | abcd_1 | abcd_2 | abcd_3 | abcd_4 | abcd_5 | abcd_6 | abcd_7 | abcd_8 | abcd_9 | abcd_10 | abcd_11 | abcd_12 | abcd_13 | abcd_14;\n assign out_pos = ~(abcd_0 & abcd_1 & abcd_2 & abcd_3 & abcd_4 & abcd_5 & abcd_6 & abcd_7 & abcd_8 & abcd_9 & abcd_10 & abcd_11 & abcd_12 & abcd_13 & abcd_14);\n\nendmodule", "error": "6: : It was declared here as a net.\n12: error: 'out_pos' has already been declared in this scope.\n7: : It was declared here as a net.\n11: error: 'out_sop' has already been declared in this scope.\n"} {"task_id": "ece241_2013_q4", "description": "A large reservior of water serves several users. In order to keep the level of water succificently high, three sensors are placed vertically at 5-inch intervals. When the water level is above the highest sensor s[3], the input flow rate should be zero. When the level is below the lowest sensor s[1], the flow rate should be at maximum (both Nominal flow valve and Supplemental flow valve opened). The flow rate when the level is between the upper and lower sensors is determined by two factors: the water level and the level previous to the last sensor change. Each water level has a nominal flow rate associated with it as show in the table below. If the sensor change indicates that the previous level was lower than the current level, the flow rate should be increased by opening the Supplemental flow valve (controlled by dfr). \n// Water Level | Sensors Asserted | Nominal Flow Rate Inputs to be Asserted\n// Above s[3] | s[1], s[2], s[3] | None\n// Between s[3] and s[2] | s[1], s[2] | fr1\n// Between s[2] and s[1] | s[1] | fr1, fr2\n// Below s[1] | None | fr1, fr2, fr3\n// Also include an active-high synchronous reset that resets the state machine to a state equivalent to if the water level had been low for a long time (no sensors asserted, and all four outputs asserted).", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput [3:1] s,\n\toutput reg fr3,\n\toutput reg fr2,\n\toutput reg fr1,\n\toutput reg dfr\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput [3:1] s,\n\toutput reg fr3,\n\toutput reg fr2,\n\toutput reg fr1,\n\toutput reg dfr\n);\n parameter IDLE = 2'b00,\n FR1 = 2'b01,\n FR2 = 2'b10,\n FR3 = 2'b11;\n\n reg [1:0] state, next_state;\n reg [3:1] last_s;\n reg [3:1] next_s;\n reg [2:0] flow_rate;\n reg [2:0] next_flow_rate;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= IDLE;\n last_s <= 3'b000;\n flow_rate <= 3'b000;\n end else begin\n state <= next_state;\n last_s <= next_s;\n flow_rate <= next_flow_rate;\n end\n end\n\n always @(*) begin\n case (state)\n IDLE: begin\n next_state = IDLE;\n next_s = s;\n next_flow_rate = 3'b000;\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n if (s[3] == 1) begin\n next_state = IDLE;\n next_s = s;\n next_flow_rate = 3'b000;\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n end else if (s[2] == 1) begin\n next_state = FR1;\n next_s = s;\n next_flow_rate = 3'b001;\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n end else if (s[1] == 1) begin\n next_state = FR2;\n next_s = s;\n next_flow_rate = 3'b010;\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end else if (s[0] == 1) begin\n next_state = FR3;\n next_s = s;\n next_flow_rate = 3'b100;\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end\n end\n FR1: begin\n next_state = FR1;\n next_s = s;\n next_flow_rate = 3'b001;\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n if (s[3] == 1) begin\n next_state = IDLE;\n next_s = s;\n next_flow_rate = 3'b000;\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n end else if (s[2] == 1) begin\n next_state = FR1;\n next_s = s;\n next_flow_rate = 3'b001;\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n end else if (s[1] == 1) begin\n next_state = FR2;\n next_s = s;\n next_flow_rate = 3'b010;\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end else if (s[0] == 1) begin\n next_state = FR3;\n next_s = s;\n next_flow_rate = 3'b100;\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end\n end\n FR2: begin\n next_state = FR2;\n next_s = s;\n next_flow_rate = 3'b010;\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n if (s[3] == 1) begin\n next_state = IDLE;\n next_s = s;\n next_flow_rate = 3'b000;\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n end else if (s[2] == 1) begin\n next_state = FR1;\n next_s = s;\n next_flow_rate = 3'b001;\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n end else if (s[1] == 1) begin\n next_state = FR2;\n next_s = s;\n next_flow_rate = 3'b010;\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end else if (s[0] == 1) begin\n next_state = FR3;\n next_s = s;\n next_flow_rate = 3'b100;\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end\n end\n FR3: begin\n next_state = FR3;\n next_s = s;\n next_flow_rate = 3'b100;\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n if (s[3] == 1) begin\n next_state = IDLE;\n next_s = s;\n next_flow_rate = 3'b000;\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n end else if (s[2] == 1) begin\n next_state = FR1;\n next_s = s;\n next_flow_rate = 3'b001;\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n end else if (s[1] == 1) begin\n next_state = FR2;\n next_s = s;\n next_flow_rate = 3'b010;\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end else if (s[0] == 1) begin\n next_state = FR3;\n next_s = s;\n next_flow_rate = 3'b100;\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end\n end\n endcase\n end\n\n always @(*) begin\n if (last_s[3] == 1) begin\n fr3 = 0;\n fr2 = 0;\n fr1 = 0;\n dfr = 0;\n end else if (last_s[2] == 1) begin\n fr3 = 0;\n fr2 = 0;\n fr1 = 1;\n dfr = 0;\n end else if (last_s[1] == 1) begin\n fr3 = 0;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end else if (last_s[0] == 1) begin\n fr3 = 1;\n fr2 = 1;\n fr1 = 1;\n dfr = 0;\n end\n end\n\nendmodule", "error": "109: warning: Constant bit select [0] is before vector s[3:1].\n151: warning: Constant bit select [0] is before vector s[3:1].\n109: : Replacing select with a constant 1'bx.\n151: : Replacing select with a constant 1'bx.\n222: : Replacing select with a constant 1'bx.\n222: warning: Constant bit select [0] is before vector last_s[3:1].\n193: warning: Constant bit select [0] is before vector s[3:1].\n67: : Replacing select with a constant 1'bx.\n193: : Replacing select with a constant 1'bx.\n67: warning: Constant bit select [0] is before vector s[3:1].\n"} {"task_id": "ece241_2013_q4", "description": "A large reservior of water serves several users. In order to keep the level of water succificently high, three sensors are placed vertically at 5-inch intervals. When the water level is above the highest sensor s[3], the input flow rate should be zero. When the level is below the lowest sensor s[1], the flow rate should be at maximum (both Nominal flow valve and Supplemental flow valve opened). The flow rate when the level is between the upper and lower sensors is determined by two factors: the water level and the level previous to the last sensor change. Each water level has a nominal flow rate associated with it as show in the table below. If the sensor change indicates that the previous level was lower than the current level, the flow rate should be increased by opening the Supplemental flow valve (controlled by dfr). \n// Water Level | Sensors Asserted | Nominal Flow Rate Inputs to be Asserted\n// Above s[3] | s[1], s[2], s[3] | None\n// Between s[3] and s[2] | s[1], s[2] | fr1\n// Between s[2] and s[1] | s[1] | fr1, fr2\n// Below s[1] | None | fr1, fr2, fr3\n// Also include an active-high synchronous reset that resets the state machine to a state equivalent to if the water level had been low for a long time (no sensors asserted, and all four outputs asserted).", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput [3:1] s,\n\toutput reg fr3,\n\toutput reg fr2,\n\toutput reg fr1,\n\toutput reg dfr\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput [3:1] s,\n\toutput reg fr3,\n\toutput reg fr2,\n\toutput reg fr1,\n\toutput reg dfr\n);\n parameter IDLE = 2'h0; // Outputs are turned off; no flow; no pumping\n parameter PUMPING = 2'h1; // Pump is on; No outputs; Water is added\n parameter FLOWING = 2'h2; // No outputs; No water is added\n\n reg prev_s = 2'h0;\n reg [1:0] state = IDLE;\n\n //Water level 1\n //sensor s1\n //sensor s2\n //sensor s3\n //Water level 2\n //sensor s1\n //sensor s2\n //Flow rate fr1 \n //Supplemental flow rate dfr\n //Water level 3\n //sensor s1\n //Flow rate fr1\n //Flow rate fr2\n //Water level 4\n //Flow rate fr1\n //Flow rate fr2\n //flow rate fr3\n\n always @ (posedge clk) begin\n if (reset) begin\n state <= IDLE;\n prev_s <= 2'h0;\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else begin\n case (state)\n IDLE : begin\n if (s[3]) begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else if (s[3] !== prev_s[3]) begin\n if (s[2] && s[1]) begin\n fr3 <= 1'b0;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else if (s[2] && !s[1]) begin\n fr3 <= 1'b0;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b0;\n end\n else if (!s[2] && !s[1]) begin\n fr3 <= 1'b0;\n fr2 <= 1'b1;\n fr1 <= 1'b0;\n dfr <= 1'b0;\n end\n end\n prev_s <= s;\n state <= FLOWING;\n end\n FLOWING : begin\n if (s[3] && !prev_s[3]) begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else if (s[3] && prev_s[3]) begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else if (!s[3] && prev_s[3]) begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else if (!s[3] && !prev_s[3]) begin\n fr3 <= 1'b0;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n prev_s <= s;\n end\n PUMPING : begin\n if (s[3]) begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n else begin\n fr3 <= 1'b1;\n fr2 <= 1'b1;\n fr1 <= 1'b1;\n dfr <= 1'b1;\n end\n state <= FLOWING;\n end\n endcase\n end\n end\nendmodule", "error": "77: error: can not select part of scalar: prev_s\n53: error: Unable to elaborate condition expression.\n77: error: Unable to elaborate condition expression.\n53: error: can not select part of scalar: prev_s\n"} {"task_id": "ece241_2014_q1c", "description": "Assume that you have two 8-bit 2's complement numbers, a[7:0] and b[7:0]. These numbers are added to produce s[7:0]. Also compute whether a (signed) overflow has occurred.", "module_header": "module top_module (\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput [7:0] s,\n\toutput overflow\n);\n", "original_code": "module top_module (\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput [7:0] s,\n\toutput overflow\n);\n reg [7:0] s;\n reg overflow;\n\n always @(*) begin\n s = a + b;\n overflow = (a[7] == b[7] && a[7] != s[7]);\n end\n\nendmodule", "error": "7: error: 's' has already been declared in this scope.\n4: : It was declared here as a net.\n8: error: 'overflow' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "ece241_2014_q1c", "description": "Assume that you have two 8-bit 2's complement numbers, a[7:0] and b[7:0]. These numbers are added to produce s[7:0]. Also compute whether a (signed) overflow has occurred.", "module_header": "module top_module (\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput [7:0] s,\n\toutput overflow\n);\n", "original_code": "module top_module (\n\tinput [7:0] a,\n\tinput [7:0] b,\n\toutput [7:0] s,\n\toutput overflow\n);\n reg [8:0] temp;\n reg overflow;\n \n always @(*) begin\n temp = a + b;\n if (temp[8] == 1) begin\n overflow = 1;\n end else begin\n overflow = 0;\n end\n s = temp[7:0];\n end\n \nendmodule", "error": "8: error: 'overflow' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "ece241_2014_q3", "description": "For the following Karnaugh map, give the circuit implementation using one 4-to-1 multiplexer and as many 2-to-1 multiplexers as required, but using as few as possible. You are not allowed to use any other logic gate and you must use _a_ and _b_ as the multiplexer selector inputs, as shown on the 4-to-1 multiplexer below.\n\n// ab\n// cd 00 01 11 10\n// 00 | 0 | 0 | 0 | 1 |\n// 01 | 1 | 0 | 0 | 0 |\n// 11 | 1 | 0 | 1 | 1 |\n// 10 | 1 | 0 | 0 | 1 |\n\n// Consider a block diagram with inputs 'c' and 'd' going into a module called \"top_module\". This \"top_module\" has four outputs, mux_in[3:0], that connect to a four input mux. The mux takes as input {a,b} and ab = 00 is connected to mux_in[0], ab=01 is connected to mux_in[1], and so in. You are implementing in Verilog just the portion labelled \"top_module\", such that the entire circuit (including the 4-to-1 mux) implements the K-map.\n", "module_header": "module top_module (\n\tinput c,\n\tinput d,\n\toutput [3:0] mux_in\n);\n", "original_code": "module top_module (\n\tinput c,\n\tinput d,\n\toutput [3:0] mux_in\n);\n wire [1:0] ab;\n wire [3:0] mux_out;\n\n // Implementing the 4-to-1 multiplexer\n mux_4to1 mux_4to1_inst (\n .in0(mux_in[0]),\n .in1(mux_in[1]),\n .in2(mux_in[2]),\n .in3(mux_in[3]),\n .sel({ab[1], ab[0]}),\n .out(mux_out)\n );\n\n // Implementing the 2-to-1 multiplexers\n mux_2to1 mux_2to1_inst1 (\n .in0(mux_out[0]),\n .in1(mux_out[1]),\n .sel(c),\n .out(mux_in[2])\n );\n\n mux_2to1 mux_2to1_inst2 (\n .in0(mux_out[2]),\n .in1(mux_out[3]),\n .sel(c),\n .out(mux_in[3])\n );\n\n mux_2to1 mux_2to1_inst3 (\n .in0(mux_in[2]),\n .in1(mux_in[3]),\n .sel(d),\n .out(mux_in[1])\n );\n\n mux_2to1 mux_2to1_inst4 (\n .in0(mux_in[0]),\n .in1(mux_in[1]),\n .sel(d),\n .out(mux_in[0])\n );\n\nendmodule", "error": "20: error: Unknown module type: mux_2to1\n10: error: Unknown module type: mux_4to1\n34: error: Unknown module type: mux_2to1\n27: error: Unknown module type: mux_2to1\n41: error: Unknown module type: mux_2to1\n"} {"task_id": "ece241_2014_q3", "description": "For the following Karnaugh map, give the circuit implementation using one 4-to-1 multiplexer and as many 2-to-1 multiplexers as required, but using as few as possible. You are not allowed to use any other logic gate and you must use _a_ and _b_ as the multiplexer selector inputs, as shown on the 4-to-1 multiplexer below.\n\n// ab\n// cd 00 01 11 10\n// 00 | 0 | 0 | 0 | 1 |\n// 01 | 1 | 0 | 0 | 0 |\n// 11 | 1 | 0 | 1 | 1 |\n// 10 | 1 | 0 | 0 | 1 |\n\n// Consider a block diagram with inputs 'c' and 'd' going into a module called \"top_module\". This \"top_module\" has four outputs, mux_in[3:0], that connect to a four input mux. The mux takes as input {a,b} and ab = 00 is connected to mux_in[0], ab=01 is connected to mux_in[1], and so in. You are implementing in Verilog just the portion labelled \"top_module\", such that the entire circuit (including the 4-to-1 mux) implements the K-map.\n", "module_header": "module top_module (\n\tinput c,\n\tinput d,\n\toutput [3:0] mux_in\n);\n", "original_code": "module top_module (\n\tinput c,\n\tinput d,\n\toutput [3:0] mux_in\n);\n wire [3:0] mux_in;\n assign mux_in[0] = ~(c | d);\n assign mux_in[1] = ~(c & d);\n assign mux_in[2] = ~(c & ~d);\n assign mux_in[3] = ~(~c & d);\n\nendmodule", "error": "6: error: 'mux_in' has already been declared in this scope.\n4: : It was declared here as a net.\n"} {"task_id": "ece241_2014_q4", "description": "Given the finite state machine circuit described below, assume that the D flip-flops are initially reset to zero before the machine begins.\n\n// Build this circuit in Verilog.\n\n// Input x goes to three different two-input gates: a XOR, an AND, and a OR gate. Each of the three gates is connected to the input of a D flip-flop and then the flip-flop outputs all go to a three-input XNOR, whose output is Z. The second input of the XOR is its corresponding flip-flop's output, the second input of the AND is its corresponding flip-flop's complemented output, and finally the second input of the OR is its corresponding flip-flop's complementary output.", "module_header": "module top_module (\n\tinput clk,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput x,\n\toutput z\n);\n // The initial state is all reset to zero before the machine begins.\n reg a, b, c;\n wire w1, w2, w3;\n reg xor2_out, and2_out, or2_out;\n always @(posedge clk) begin\n a <= 1'b0;\n b <= 1'b0;\n c <= 1'b0;\n end\n\n // The D flip-flops outputs go to a three-input XNOR, whose output is Z.\n xor2 xor2(.a(x), .b(xor2_out), .z(w1));\n and2 and2(.a(x), .b(~and2_out), .z(w2));\n or2 or2(.a(x), .b(~or2_out), .z(w3));\n xnor3 xnor3(.a(w1), .b(w2), .c(w3), .z(z));\n\n // The D flip-flops are connected to three different two-input gates.\n dffr dffr1(.clk(clk), .d(x), .q(xor2_out));\n dffr dffr2(.clk(clk), .d(~xor2_out), .q(and2_out));\n dffr dffr3(.clk(clk), .d(~and2_out), .q(or2_out));\nendmodule", "error": "20: error: Unknown module type: xnor3\n18: error: Unknown module type: and2\n23: error: Unknown module type: dffr\n25: error: Unknown module type: dffr\n17: error: Unknown module type: xor2\n19: error: Unknown module type: or2\n24: error: Unknown module type: dffr\n"} {"task_id": "ece241_2014_q4", "description": "Given the finite state machine circuit described below, assume that the D flip-flops are initially reset to zero before the machine begins.\n\n// Build this circuit in Verilog.\n\n// Input x goes to three different two-input gates: a XOR, an AND, and a OR gate. Each of the three gates is connected to the input of a D flip-flop and then the flip-flop outputs all go to a three-input XNOR, whose output is Z. The second input of the XOR is its corresponding flip-flop's output, the second input of the AND is its corresponding flip-flop's complemented output, and finally the second input of the OR is its corresponding flip-flop's complementary output.", "module_header": "module top_module (\n\tinput clk,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput x,\n\toutput z\n);\n wire n1;\n wire n2;\n wire n3;\n wire n4;\n wire n5;\n wire n6;\n wire n7;\n wire n8;\n\n DFFRX_X1 I0 ( .D(n7), .CK(clk), .RN(1'b1), .Q(n1) );\n DFFRX_X1 I1 ( .D(n8), .CK(clk), .RN(1'b1), .Q(n2) );\n DFFRX_X1 I2 ( .D(n6), .CK(clk), .RN(1'b1), .Q(n3) );\n DFFRX_X1 I3 ( .D(n5), .CK(clk), .RN(1'b1), .Q(n4) );\n XOR2_X1 I4 ( .A(x), .B(n1), .Z(n5) );\n AND2_X1 I5 ( .A(n1), .B(n2), .Z(n6) );\n OR2_X1 I6 ( .A(n1), .B(n3), .Z(n7) );\n OR2_X1 I7 ( .A(n4), .B(n2), .Z(n8) );\n XNOR2_X1 I8 ( .A(n3), .B(n4), .Z(z) );\nendmodule", "error": "22: error: Unknown module type: OR2_X1\n18: error: Unknown module type: DFFRX_X1\n15: error: Unknown module type: DFFRX_X1\n21: error: Unknown module type: OR2_X1\n17: error: Unknown module type: DFFRX_X1\n23: error: Unknown module type: XNOR2_X1\n19: error: Unknown module type: XOR2_X1\n20: error: Unknown module type: AND2_X1\n16: error: Unknown module type: DFFRX_X1\n"} {"task_id": "ece241_2014_q5a", "description": "You are to design a one-input one-output serial 2's complementer Moore state machine. The input (x) is a series of bits (one per clock cycle) beginning with the least-significant bit of the number, and the output (Z) is the 2's complement of the input. The machine will accept input numbers of arbitrary length. The circuit requires a positive edge triggered asynchronous reset. The conversion begins when Reset is released and stops when Reset is asserted.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n // Synchronous reset\n reg [1:0] state;\n parameter S0 = 2'b00, S1 = 2'b01, S2 = 2'b10;\n\n always @(posedge clk or negedge areset) begin\n // always block triggered on positive edge of clock signal or negative edge of asynchronous reset signal.\n if (!areset) begin\n // If asynchronous reset is active.\n state <= S0; // Set state to S0.\n z <= 1'b0; // Set output z to 0.\n end\n else begin\n // If asynchronous reset is not active.\n case (state)\n // Switching between states.\n S0: begin\n // State S0\n if (x) begin\n // If input x is true.\n state <= S1; // Move to state S1.\n z <= 1'b1; // Set output z to 1.\n end\n else begin\n // If input x is false.\n state <= S0; // Stay in state S0.\n z <= 1'b0; // Set output z to 0.\n end\n end\n S1: begin\n // State S1\n if (x) begin\n // If input x is true.\n state <= S2; // Move to state S2.\n z <= 1'b0; // Set output z to 0.\n end\n else begin\n // If input x is false.\n state <= S0; // Move to state S0.\n z <= 1'b1; // Set output z to 1.\n end\n end\n S2: begin\n // State S2\n if (x) begin\n // If input x is true.\n state <= S1; // Move to state S1.\n z <= 1'b1; // Set output z to 1.\n end\n else begin\n // If input x is false.\n state <= S0; // Move to state S0.\n z <= 1'b0; // Set output z to 0.\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "40: error: 'z' is not a valid l-value for a procedural assignment.\n53: error: 'z' is not a valid l-value for a procedural assignment.\n5: : 'z' is declared here as a wire.\n27: error: 'z' is not a valid l-value for a procedural assignment.\n32: error: 'z' is not a valid l-value for a procedural assignment.\n16: error: 'z' is not a valid l-value for a procedural assignment.\n45: error: 'z' is not a valid l-value for a procedural assignment.\n58: error: 'z' is not a valid l-value for a procedural assignment.\n"} {"task_id": "ece241_2014_q5a", "description": "You are to design a one-input one-output serial 2's complementer Moore state machine. The input (x) is a series of bits (one per clock cycle) beginning with the least-significant bit of the number, and the output (Z) is the 2's complement of the input. The machine will accept input numbers of arbitrary length. The circuit requires a positive edge triggered asynchronous reset. The conversion begins when Reset is released and stops when Reset is asserted.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n // Synchronous reset\n\treg [1:0] state;\n\tparameter S0 = 2'b00, S1 = 2'b01, S2 = 2'b10;\n\n\talways @(posedge clk or negedge areset) begin\n\t\tif (areset == 0) begin\n\t\t\tstate <= S0;\n\t\tend else begin\n\t\t\tcase (state)\n\t\t\t\tS0: begin\n\t\t\t\t\tif (x == 1) begin\n\t\t\t\t\t\tstate <= S1;\n\t\t\t\t\tend else begin\n\t\t\t\t\t\tstate <= S0;\n\t\t\t\t\tend\n\t\t\t\tend\n\t\t\t\tS1: begin\n\t\t\t\t\tif (x == 1) begin\n\t\t\t\t\t\tstate <= S2;\n\t\t\t\t\tend else begin\n\t\t\t\t\t\tstate <= S0;\n\t\t\t\t\tend\n\t\t\t\tend\n\t\t\t\tS2: begin\n\t\t\t\t\tif (x == 1) begin\n\t\t\t\t\t\tstate <= S2;\n\t\t\t\t\tend else begin\n\t\t\t\t\t\tstate <= S0;\n\t\t\t\t\tend\n\t\t\t\tend\n\t\t\tendcase\n\t\tend\n\tend\n\n\talways @(posedge clk or negedge areset) begin\n\t\tif (areset == 0) begin\n\t\t\tz <= 0;\n\t\tend else begin\n\t\t\tcase (state)\n\t\t\t\tS0: begin\n\t\t\t\t\tz <= 0;\n\t\t\t\tend\n\t\t\t\tS1: begin\n\t\t\t\t\tz <= ~x;\n\t\t\t\tend\n\t\t\t\tS2: begin\n\t\t\t\t\tz <= ~x;\n\t\t\t\tend\n\t\t\tendcase\n\t\tend\n\tend\n\nendmodule", "error": "53: error: 'z' is not a valid l-value for a procedural assignment.\n5: : 'z' is declared here as a wire.\n43: error: 'z' is not a valid l-value for a procedural assignment.\n50: error: 'z' is not a valid l-value for a procedural assignment.\n47: error: 'z' is not a valid l-value for a procedural assignment.\n"} {"task_id": "ece241_2014_q5b", "description": "The following diagram is a Mealy machine implementation of the 2's complementer. Implement in Verilog using one-hot encoding. Resets into state A and reset is asynchronous active-high.\n\n// A --x=0 (z=0)--> A\n// A --x=1 (z=1)--> B\n// B --x=0 (z=1)--> B\n// B --x=1 (z=0)--> B", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n\n reg [1:0] state;\n reg z;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= A;\n z <= 0;\n end else begin\n case (state)\n A: begin\n if (x) begin\n state <= B;\n z <= 1;\n end else begin\n state <= A;\n z <= 0;\n end\n end\n B: begin\n if (x) begin\n state <= D;\n z <= 0;\n end else begin\n state <= C;\n z <= 1;\n end\n end\n C: begin\n if (x) begin\n state <= D;\n z <= 0;\n end else begin\n state <= C;\n z <= 1;\n end\n end\n D: begin\n if (x) begin\n state <= B;\n z <= 1;\n end else begin\n state <= A;\n z <= 0;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "13: error: 'z' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "ece241_2014_q5b", "description": "The following diagram is a Mealy machine implementation of the 2's complementer. Implement in Verilog using one-hot encoding. Resets into state A and reset is asynchronous active-high.\n\n// A --x=0 (z=0)--> A\n// A --x=1 (z=1)--> B\n// B --x=0 (z=1)--> B\n// B --x=1 (z=0)--> B", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput x,\n\toutput z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n parameter F = 2'b101;\n\n reg [2:0] state;\n reg z_reg;\n\n always @(posedge clk, posedge areset) begin\n if (areset) begin\n state <= A;\n z_reg <= 1'b0;\n end\n else begin\n case (state)\n A: begin\n if (x) begin\n state <= B;\n z_reg <= 1'b1;\n end\n else begin\n state <= A;\n z_reg <= 1'b0;\n end\n end\n B: begin\n if (x) begin\n state <= C;\n z_reg <= 1'b0;\n end\n else begin\n state <= B;\n z_reg <= 1'b1;\n end\n end\n C: begin\n if (x) begin\n state <= D;\n z_reg <= 1'b1;\n end\n else begin\n state <= C;\n z_reg <= 1'b0;\n end\n end\n D: begin\n if (x) begin\n state <= E;\n z_reg <= 1'b0;\n end\n else begin\n state <= D;\n z_reg <= 1'b1;\n end\n end\n E: begin\n if (x) begin\n state <= F;\n z_reg <= 1'b1;\n end\n else begin\n state <= E;\n z_reg <= 1'b0;\n end\n end\n F: begin\n if (x) begin\n state <= A;\n z_reg <= 1'b0;\n end\n else begin\n state <= F;\n z_reg <= 1'b1;\n end\n end\n endcase\n end\n end\n\n assign z = z_reg;\n\nendmodule", "error": "12: warning: Numeric constant truncated to 2 bits.\n11: warning: Numeric constant truncated to 2 bits.\n11: warning: Extra digits given for sized binary constant.\n12: warning: Extra digits given for sized binary constant.\n"} {"task_id": "edgecapture", "description": "For each bit in a 32-bit vector, capture when the input signal changes from 1 in one clock cycle to 0 the next. \"Capture\" means that the output will remain 1 until the register is reset (active high synchronous reset).", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput [31:0] in,\n\toutput reg [31:0] out);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput [31:0] in,\n\toutput reg [31:0] out);\n // Define the flip-flops and their outputs\n reg [31:0] flip_flop_outputs;\n reg [31:0] flip_flop_inputs;\n\n // Initialize the flip-flops\n always @(posedge clk, posedge reset) begin\n if (reset) begin\n flip_flop_outputs <= 0;\n flip_flop_inputs <= 0;\n end else begin\n flip_flop_outputs <= flip_flop_inputs;\n flip_flop_inputs <= in;\n end\n end\n\n // Define the D flip-flops\n always @(posedge clk) begin\n if (flip_flop_inputs[0] == 0 && flip_flop_outputs[0] == 1) begin\n out[0] <= 1;\n end else begin\n out[0] <= 0;\n end\n\n for (i = 1; i < 32; i = i + 1) begin\n if (flip_flop_inputs[i] == 0 && flip_flop_outputs[i] == 1) begin\n out[i] <= 1;\n end else begin\n out[i] <= 0;\n end\n end\n end\n\nendmodule", "error": "29: register ``i'' unknown in top_module.\n"} {"task_id": "edgecapture", "description": "For each bit in a 32-bit vector, capture when the input signal changes from 1 in one clock cycle to 0 the next. \"Capture\" means that the output will remain 1 until the register is reset (active high synchronous reset).", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput [31:0] in,\n\toutput reg [31:0] out);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput [31:0] in,\n\toutput reg [31:0] out);\n reg [31:0] out_reg;\n\n always @(posedge clk) begin\n if (reset) begin\n out_reg <= 0;\n end else begin\n for (i = 0; i < 32; i = i + 1) begin\n if (in[i] && !in[i-1]) begin\n out_reg[i] <= 1;\n end else if (!in[i] && in[i-1]) begin\n out_reg[i] <= 0;\n end\n end\n end\n out <= out_reg;\n end\n endmodule", "error": "12: register ``i'' unknown in top_module.\n"} {"task_id": "edgedetect", "description": "For each bit in an 8-bit vector, detect when the input signal changes from 0 in one clock cycle to 1 the next (similar to positive edge detection). The output bit should be set the cycle after a 0 to 1 transition occurs.", "module_header": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] pedge);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] pedge);\n reg [7:0] in_reg;\n reg [7:0] in_next;\n reg [7:0] pedge_reg;\n reg [7:0] pedge_next;\n\n always @(posedge clk) begin\n in_reg <= in;\n in_next <= in;\n pedge_reg <= pedge;\n pedge_next <= pedge;\n end\n\n always @(posedge clk) begin\n if (in_reg == 8'b0 && in_next == 8'b1) begin\n pedge_next <= 8'b1;\n end else begin\n pedge_next <= 8'b0;\n end\n end\n\n always @(posedge clk) begin\n if (in_reg == 8'b0) begin\n pedge <= 8'b0;\n end else begin\n pedge <= pedge_next;\n end\n end\n\n assign pedge = pedge_reg;\n\n endmodule", "error": "27: error: Cannot perform procedural assignment to variable 'pedge' because it is also continuously assigned.\n29: error: Cannot perform procedural assignment to variable 'pedge' because it is also continuously assigned.\n"} {"task_id": "edgedetect", "description": "For each bit in an 8-bit vector, detect when the input signal changes from 0 in one clock cycle to 1 the next (similar to positive edge detection). The output bit should be set the cycle after a 0 to 1 transition occurs.", "module_header": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] pedge);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] pedge);\n\n reg [7:0] prev_state;\n\n always @(posedge clk) begin\n pedge <= 1'b0;\n prev_state <= in;\n for (i = 0; i < 8; i = i + 1) begin\n if (in[i] == 1 && prev_state[i] == 0) begin\n pedge[i] <= 1;\n end\n end\n end\n\n endmodule", "error": "11: register ``i'' unknown in top_module.\n"} {"task_id": "edgedetect2", "description": "For each bit in an 8-bit vector, detect when the input signal changes from one clock cycle to the next (detect any edge). The output bit should be set the cycle after a 0 to 1 transition occurs.", "module_header": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] anyedge);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput [7:0] in,\n\toutput reg [7:0] anyedge);\n\t\n\treg [7:0] prev_in;\n\t\n\talways @(posedge clk) begin\n\t\tanyedge <= 8'b0;\n\t\tfor (i = 0; i < 8; i = i + 1) begin\n\t\t\tif (in[i] == 1 && prev_in[i] == 0) begin\n\t\t\t\tanyedge[i] <= 1;\n\t\t\tend\n\t\tend\n\t\tprev_in <= in;\n\tend\nendmodule", "error": "10: register ``i'' unknown in top_module.\n"} {"task_id": "fadd", "description": "Create a full adder. A full adder adds three bits (including carry-in) and produces a sum and carry-out.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput cin,\n\toutput cout,\n\toutput sum\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput cin,\n\toutput cout,\n\toutput sum\n);\n\n\twire [3:0] s;\n\twire [3:0] c;\n\t\n\tfull_adder fa0(a[0], b[0], cin, s[0], c[0]);\n\tfull_adder fa1(a[1], b[1], c[0], s[1], c[1]);\n\tfull_adder fa2(a[2], b[2], c[1], s[2], c[2]);\n\tfull_adder fa3(a[3], b[3], c[2], s[3], cout);\n\t\n\tassign sum = {s[3], s[2], s[1], s[0]};\n\t\nendmodule", "error": "13: error: Unknown module type: full_adder\n12: error: Unknown module type: full_adder\n15: error: Unknown module type: full_adder\n14: error: Unknown module type: full_adder\n"} {"task_id": "fadd", "description": "Create a full adder. A full adder adds three bits (including carry-in) and produces a sum and carry-out.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput cin,\n\toutput cout,\n\toutput sum\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput cin,\n\toutput cout,\n\toutput sum\n);\n\tfull_adder adder (\n\t\t.a(a),\n\t\t.b(b),\n\t\t.cin(cin),\n\t\t.cout(cout),\n\t\t.sum(sum)\n\t);\n\nendmodule", "error": "8: error: Unknown module type: full_adder\n"} {"task_id": "fsm1", "description": "Consider the follow Moore machine with the diagram described below:\n\n// B (1) --0--> A\n// B (1) --1--> B\n// A (0) --0--> B\n// A (0) --1--> A\n\n// Write Verilog implementing this state machine. It should asynchronously reset into state B if reset if high.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n // Declare internal signals\n reg [1:0] state; // State variable\n wire [1:0] next_state; // Next state variable\n reg out_reg; // Output register\n\n // Define state transition logic\n always @ (posedge clk or posedge areset) begin\n if (areset) begin\n state <= 2'b01; // Reset into state B\n end else begin\n state <= next_state; // Update state on clock edge\n end\n end\n\n // Define next state logic\n always @ (*) begin\n case (state)\n 2'b01: next_state = in ? 2'b01 : 2'b10; // State B\n 2'b10: next_state = in ? 2'b10 : 2'b01; // State A\n endcase\n end\n\n // Define output logic\n always @ (*) begin\n case (state)\n 2'b01: out_reg = 1; // State B\n 2'b10: out_reg = 0; // State A\n endcase\n end\n\n // Output logic\n assign out = out_reg;\n\nendmodule", "error": "25: error: 'next_state' is not a valid l-value for a procedural assignment.\n24: error: 'next_state' is not a valid l-value for a procedural assignment.\n9: : 'next_state' is declared here as a wire.\n"} {"task_id": "fsm1", "description": "Consider the follow Moore machine with the diagram described below:\n\n// B (1) --0--> A\n// B (1) --1--> B\n// A (0) --0--> B\n// A (0) --1--> A\n\n// Write Verilog implementing this state machine. It should asynchronously reset into state B if reset if high.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n parameter A = 1'b0;\n parameter B = 1'b1;\n\n reg [0:0] current_state;\n reg [0:0] next_state;\n\n reg out;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n current_state <= B;\n out <= 1'b1;\n end else begin\n current_state <= next_state;\n case (current_state)\n A: begin\n if (in == 1'b0) begin\n next_state <= B;\n out <= 1'b0;\n end else begin\n next_state <= A;\n out <= 1'b0;\n end\n end\n B: begin\n if (in == 1'b0) begin\n next_state <= A;\n out <= 1'b0;\n end else begin\n next_state <= B;\n out <= 1'b1;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "13: error: 'out' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm1s", "description": "This is a Moore state machine with two states, one input, and one output. Implement this state machine in Verilog. The reset state is B and reset is active-high synchronous.\n\n// B (out=1) --in=0--> A\n// B (out=1) --in=1--> B\n// A (out=0) --in=0--> B\n// A (out=0) --in=1--> A", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n // Define two states A and B and initialise to B\n // The state variable should be of type integer and should take values 0 and 1\n reg [1:0] state;\n parameter [1:0] B = 2'b00;\n parameter [1:0] A = 2'b01;\n initial state = B;\n\n // In the given FSM design, out is the output of the state machine\n reg out;\n\n // In the given FSM design, in is the input to the state machine\n always @(posedge clk or posedge reset) begin\n if (reset) begin\n state <= B;\n out <= 1'b1;\n end else begin\n case(state)\n B: begin\n if (in) begin\n state <= A;\n out <= 1'b0;\n end else begin\n state <= B;\n out <= 1'b1;\n end\n end\n A: begin\n if (in) begin\n state <= A;\n out <= 1'b0;\n end else begin\n state <= B;\n out <= 1'b1;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "5: : It was declared here as a net.\n15: error: 'out' has already been declared in this scope.\n"} {"task_id": "fsm1s", "description": "This is a Moore state machine with two states, one input, and one output. Implement this state machine in Verilog. The reset state is B and reset is active-high synchronous.\n\n// B (out=1) --in=0--> A\n// B (out=1) --in=1--> B\n// A (out=0) --in=0--> B\n// A (out=0) --in=1--> A", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n parameter A = 1'b0;\n parameter B = 1'b1;\n parameter A_state = 1;\n parameter B_state = 0;\n parameter out_A = 1'b0;\n parameter out_B = 1'b1;\n\n reg [0:0] state_reg;\n wire [0:0] state_next;\n reg out_reg;\n\n always @(posedge clk, posedge reset)\n begin\n if (reset)\n begin\n state_reg <= B;\n out_reg <= out_B;\n end\n else\n begin\n state_reg <= state_next;\n out_reg <= out_A;\n end\n end\n\n always @(*)\n begin\n case (state_reg)\n B:\n begin\n state_next = in ? B : A;\n out_A = out_B;\n out_B = out_B;\n end\n A:\n begin\n state_next = in ? A : B;\n out_A = out_B;\n out_B = out_A;\n end\n default:\n begin\n state_next = B;\n out_A = out_B;\n out_B = out_B;\n end\n endcase\n end\n\n assign out = out_reg;\n\nendmodule", "error": "45: error: Could not find variable ``out_B'' in ``top_module''\n39: error: Could not find variable ``out_B'' in ``top_module''\n15: : 'state_next' is declared here as a wire.\n51: error: Could not find variable ``out_B'' in ``top_module''\n50: error: Could not find variable ``out_A'' in ``top_module''\n44: error: Could not find variable ``out_A'' in ``top_module''\n38: error: Could not find variable ``out_A'' in ``top_module''\n37: error: 'state_next' is not a valid l-value for a procedural assignment.\n43: error: 'state_next' is not a valid l-value for a procedural assignment.\n49: error: 'state_next' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm2", "description": "This is a Moore state machine with two states, two inputs, and one output. Implement this state machine in Verilog. Reset is an active-high asynchronous reset to state OFF.\n\n// OFF (out=0) --j=0--> OFF\n// OFF (out=0) --j=1--> ON\n// ON (out=1) --k=0--> ON\n// ON (out=1) --k=1--> OFF", "module_header": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput areset,\n\toutput out\n);\n // State register\n reg [1:0] state_reg;\n // Next state logic\n always @(posedge clk or posedge areset) begin\n if (areset) state_reg <= 2'b0;\n else state_reg <= next_state;\n end\n\n // Output logic\n assign out = state_reg[0];\n\n // Next state logic\n always @(*) begin\n case (state_reg)\n 2'b00: next_state = (j) ? 2'b01 : 2'b00;\n 2'b01: next_state = (k) ? 2'b10 : 2'b01;\n 2'b10: next_state = (k) ? 2'b00 : 2'b10;\n endcase\n end\n\nendmodule", "error": "22: error: Could not find variable ``next_state'' in ``top_module''\n13: error: Unable to bind wire/reg/memory `next_state' in `top_module'\n23: error: Could not find variable ``next_state'' in ``top_module''\n24: error: Could not find variable ``next_state'' in ``top_module''\n"} {"task_id": "fsm2", "description": "This is a Moore state machine with two states, two inputs, and one output. Implement this state machine in Verilog. Reset is an active-high asynchronous reset to state OFF.\n\n// OFF (out=0) --j=0--> OFF\n// OFF (out=0) --j=1--> ON\n// ON (out=1) --k=0--> ON\n// ON (out=1) --k=1--> OFF", "module_header": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput areset,\n\toutput out\n);\n parameter OFF = 1'b0;\n parameter ON = 1'b1;\n parameter OFF_STATE = 2'b00;\n parameter ON_STATE = 2'b01;\n\n reg [1:0] state, next_state;\n reg out_reg;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= OFF_STATE;\n out_reg <= OFF;\n end else begin\n state <= next_state;\n out_reg <= out;\n end\n end\n\n always @(*) begin\n case (state)\n OFF_STATE: begin\n if (j) begin\n next_state = ON_STATE;\n out = ON;\n end else begin\n next_state = OFF_STATE;\n out = OFF;\n end\n end\n ON_STATE: begin\n if (k) begin\n next_state = OFF_STATE;\n out = OFF;\n end else begin\n next_state = ON_STATE;\n out = ON;\n end\n end\n endcase\n end\n\nendmodule", "error": "34: error: 'out' is not a valid l-value for a procedural assignment.\n40: error: 'out' is not a valid l-value for a procedural assignment.\n31: error: 'out' is not a valid l-value for a procedural assignment.\n6: : 'out' is declared here as a wire.\n43: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm2s", "description": "This is a Moore state machine with two states, two inputs, and one output. Implement this state machine in Verilog. Reset is an active-high synchronous reset to state OFF.\n\n// OFF (out=0) --j=0--> OFF\n// OFF (out=0) --j=1--> ON\n// ON (out=1) --k=0--> ON\n// ON (out=1) --k=1--> OFF", "module_header": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput reset,\n\toutput out\n);\n parameter OFF = 1'b0;\n parameter ON = 1'b1;\n parameter OFF_OFF = 2'b00;\n parameter OFF_ON = 2'b01;\n parameter ON_OFF = 2'b10;\n parameter ON_ON = 2'b11;\n\n reg [1:0] state, next_state;\n reg out;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= OFF;\n end else begin\n state <= next_state;\n end\n end\n\n always @(*) begin\n case (state)\n OFF: begin\n if (j == 1 && k == 0) begin\n next_state = ON;\n end else if (j == 0 && k == 1) begin\n next_state = OFF;\n end else begin\n next_state = OFF;\n end\n end\n ON: begin\n if (j == 1 && k == 0) begin\n next_state = ON;\n end else if (j == 0 && k == 1) begin\n next_state = OFF;\n end else begin\n next_state = ON;\n end\n end\n endcase\n end\n\n always @(*) begin\n case (state)\n OFF: begin\n out = 1'b0;\n end\n ON: begin\n out = 1'b1;\n end\n endcase\n end\n\nendmodule", "error": "16: error: 'out' has already been declared in this scope.\n6: : It was declared here as a net.\n"} {"task_id": "fsm2s", "description": "This is a Moore state machine with two states, two inputs, and one output. Implement this state machine in Verilog. Reset is an active-high synchronous reset to state OFF.\n\n// OFF (out=0) --j=0--> OFF\n// OFF (out=0) --j=1--> ON\n// ON (out=1) --k=0--> ON\n// ON (out=1) --k=1--> OFF", "module_header": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput j,\n\tinput k,\n\tinput reset,\n\toutput out\n);\n parameter OFF = 1'b0;\n parameter ON = 1'b1;\n parameter OFF_ = 1'b0;\n parameter ON_ = 1'b1;\n\n reg [1:0] state, next_state;\n reg out_reg;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= OFF;\n out_reg <= OFF_;\n end else begin\n state <= next_state;\n out_reg <= state;\n end\n end\n\n always @(*) begin\n case(state)\n OFF: begin\n if (j) begin\n next_state = ON;\n out = ON_;\n end else begin\n next_state = OFF;\n out = OFF_;\n end\n end\n ON: begin\n if (k) begin\n next_state = OFF;\n out = OFF_;\n end else begin\n next_state = ON;\n out = ON_;\n end\n end\n endcase\n end\n\nendmodule", "error": "34: error: 'out' is not a valid l-value for a procedural assignment.\n40: error: 'out' is not a valid l-value for a procedural assignment.\n31: error: 'out' is not a valid l-value for a procedural assignment.\n6: : 'out' is declared here as a wire.\n43: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Implement this state machine. Include a positive edge triggered asynchronous reset that resets the FSM to state A.\n \n// state | next state in=0, next state in=1 | output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n // State variables\n reg [1:0] state; // State variable with 2 bits\n reg [1:0] next_state; // Next state variable\n reg [1:0] out_state; // Output variable\n\n // State definitions\n parameter [1:0] STATE_A = 2'b00;\n parameter [1:0] STATE_B = 2'b01;\n parameter [1:0] STATE_C = 2'b10;\n parameter [1:0] STATE_D = 2'b11;\n\n // State transition table\n always @(posedge clk, posedge areset) begin\n if (areset) begin\n state <= STATE_A;\n out <= 1'b0; // Initialize output to 0\n end else begin\n state <= next_state;\n case (state)\n STATE_A: begin\n out <= 1'b0;\n if (in) begin\n next_state <= STATE_B;\n end else begin\n next_state <= STATE_A;\n end\n end\n STATE_B: begin\n out <= 1'b0;\n if (in) begin\n next_state <= STATE_B;\n end else begin\n next_state <= STATE_C;\n end\n end\n STATE_C: begin\n out <= 1'b0;\n if (in) begin\n next_state <= STATE_D;\n end else begin\n next_state <= STATE_A;\n end\n end\n STATE_D: begin\n out <= 1'b1;\n if (in) begin\n next_state <= STATE_B;\n end else begin\n next_state <= STATE_C;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "5: : 'out' is declared here as a wire.\n22: error: 'out' is not a valid l-value for a procedural assignment.\n35: error: 'out' is not a valid l-value for a procedural assignment.\n51: error: 'out' is not a valid l-value for a procedural assignment.\n27: error: 'out' is not a valid l-value for a procedural assignment.\n43: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Implement this state machine. Include a positive edge triggered asynchronous reset that resets the FSM to state A.\n \n// state | next state in=0, next state in=1 | output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput areset,\n\toutput out\n);\n // state register\n reg [1:0] state;\n // next state logic\n always @(posedge clk or posedge areset) begin\n if (areset)\n state <= 2'b00; // reset to state A\n else\n state <= next_state;\n end\n // output logic\n assign out = (state == 2'b10) ? 1 : 0;\n // next state logic\n always @* begin\n case (state)\n 2'b00: next_state = (in == 0) ? 2'b00 : 2'b01;\n 2'b01: next_state = (in == 0) ? 2'b01 : 2'b01;\n 2'b10: next_state = (in == 0) ? 2'b00 : 2'b01;\n 2'b11: next_state = (in == 0) ? 2'b01 : 2'b01;\n endcase\n end\nendmodule", "error": "23: error: Could not find variable ``next_state'' in ``top_module''\n24: error: Could not find variable ``next_state'' in ``top_module''\n21: error: Could not find variable ``next_state'' in ``top_module''\n22: error: Could not find variable ``next_state'' in ``top_module''\n14: error: Unable to bind wire/reg/memory `next_state' in `top_module'\n"} {"task_id": "fsm3comb", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following state encoding: A=2'b00, B=2'b01, C=2'b10, D=2'b11.Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. Given the current state (state), compute the next_state and output (out) based on the state transition table.\n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput in,\n\tinput [1:0] state,\n\toutput reg [1:0] next_state,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [1:0] state,\n\toutput reg [1:0] next_state,\n\toutput out\n);\n // State transition logic\n always @(*) begin\n case (state)\n 2'b00: next_state = in ? 2'b01 : 2'b00; // A to B\n 2'b01: next_state = in ? 2'b10 : 2'b01; // B to C or B to B\n 2'b10: next_state = in ? 2'b00 : 2'b11; // C to A or C to D\n 2'b11: next_state = in ? 2'b01 : 2'b10; // D to B or D to C\n endcase\n end\n\n // Output logic\n always @(*) begin\n case (state)\n 2'b00, 2'b01: out = 1'b0; // A, B states\n 2'b10, 2'b11: out = 1'b1; // C, D states\n endcase\n end\n\nendmodule", "error": "5: : 'out' is declared here as a wire.\n21: error: 'out' is not a valid l-value for a procedural assignment.\n20: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3comb", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following state encoding: A=2'b00, B=2'b01, C=2'b10, D=2'b11.Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. Given the current state (state), compute the next_state and output (out) based on the state transition table.\n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput in,\n\tinput [1:0] state,\n\toutput reg [1:0] next_state,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [1:0] state,\n\toutput reg [1:0] next_state,\n\toutput out\n);\n // State transition logic\n always @* begin\n case (state)\n 2'b00: next_state = (in == 1'b0) ? 2'b00 : 2'b01; // A\n 2'b01: next_state = (in == 1'b0) ? 2'b10 : 2'b01; // B\n 2'b10: next_state = (in == 1'b0) ? 2'b00 : 2'b11; // C\n 2'b11: next_state = (in == 1'b0) ? 2'b10 : 2'b01; // D\n default: next_state = 2'b00; // Default to state A\n endcase\n end\n\n // Output logic\n always @* begin\n case (state)\n 2'b00, 2'b01, 2'b10: out = 1'b0; // Output 0 for states A, B, C\n 2'b11: out = 1'b1; // Output 1 for state D\n default: out = 1'b0; // Default to output 0\n endcase\n end\n\nendmodule", "error": "5: : 'out' is declared here as a wire.\n21: error: 'out' is not a valid l-value for a procedural assignment.\n22: error: 'out' is not a valid l-value for a procedural assignment.\n23: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3onehot", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following one-hot state encoding: A=4'b0001, B=4'b0010, C=4'b0100, D=4'b1000. Derive state transition and output logic equations by inspection assuming a one-hot encoding. Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. \n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput in,\n\tinput [3:0] state,\n\toutput reg [3:0] next_state,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [3:0] state,\n\toutput reg [3:0] next_state,\n\toutput out\n);\n // State transition logic\n always @(*) begin\n case(state)\n 4'b0001: if(in == 1'b0) next_state = 4'b0001; else next_state = 4'b0010;\n 4'b0010: if(in == 1'b0) next_state = 4'b0010; else next_state = 4'b0100;\n 4'b0100: if(in == 1'b0) next_state = 4'b0001; else next_state = 4'b1000;\n 4'b1000: if(in == 1'b0) next_state = 4'b0100; else next_state = 4'b0010;\n endcase\n end\n\n // Output logic\n always @(*) begin\n case(state)\n 4'b0001: out = 1'b0;\n 4'b0010: out = 1'b0;\n 4'b0100: out = 1'b0;\n 4'b1000: out = 1'b1;\n endcase\n end\n\nendmodule", "error": "5: : 'out' is declared here as a wire.\n22: error: 'out' is not a valid l-value for a procedural assignment.\n21: error: 'out' is not a valid l-value for a procedural assignment.\n23: error: 'out' is not a valid l-value for a procedural assignment.\n20: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3onehot", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following one-hot state encoding: A=4'b0001, B=4'b0010, C=4'b0100, D=4'b1000. Derive state transition and output logic equations by inspection assuming a one-hot encoding. Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. \n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput in,\n\tinput [3:0] state,\n\toutput reg [3:0] next_state,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [3:0] state,\n\toutput reg [3:0] next_state,\n\toutput out\n);\n always @(*) begin\n case(state)\n 4'b0001: begin // State A\n if(in == 1'b0) begin\n next_state = 4'b0001; // Stay in state A\n end else begin\n next_state = 4'b0010; // Transition to state B\n end\n out = 1'b0; // Output 0\n end\n 4'b0010: begin // State B\n if(in == 1'b0) begin\n next_state = 4'b0010; // Stay in state B\n end else begin\n next_state = 4'b0100; // Transition to state C\n end\n out = 1'b0; // Output 0\n end\n 4'b0100: begin // State C\n if(in == 1'b0) begin\n next_state = 4'b0001; // Transition to state A\n end else begin\n next_state = 4'b1000; // Transition to state D\n end\n out = 1'b0; // Output 0\n end\n 4'b1000: begin // State D\n if(in == 1'b0) begin\n next_state = 4'b0100; // Transition to state C\n end else begin\n next_state = 4'b0010; // Transition to state B\n end\n out = 1'b1; // Output 1\n end\n endcase\n end\nendmodule", "error": "5: : 'out' is declared here as a wire.\n39: error: 'out' is not a valid l-value for a procedural assignment.\n23: error: 'out' is not a valid l-value for a procedural assignment.\n31: error: 'out' is not a valid l-value for a procedural assignment.\n15: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3s", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Implement this state machine. Include a synchronous active high reset that resets the FSM to state A. \n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n parameter A = 2'b00, B = 2'b01, C = 2'b10, D = 2'b11;\n\n reg [1:0] state, next_state;\n\n always @ (posedge clk, posedge reset)\n begin\n if (reset)\n state <= A;\n else\n state <= next_state;\n end\n\n always @ (state, in)\n begin\n case (state)\n A: begin\n out = 0;\n if (in == 0)\n next_state = A;\n else\n next_state = B;\n end\n B: begin\n out = 0;\n if (in == 0)\n next_state = C;\n else\n next_state = B;\n end\n C: begin\n out = 0;\n if (in == 0)\n next_state = A;\n else\n next_state = D;\n end\n D: begin\n out = 1;\n if (in == 0)\n next_state = C;\n else\n next_state = B;\n end\n endcase\n end\nendmodule", "error": "37: error: 'out' is not a valid l-value for a procedural assignment.\n5: : 'out' is declared here as a wire.\n30: error: 'out' is not a valid l-value for a procedural assignment.\n44: error: 'out' is not a valid l-value for a procedural assignment.\n23: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm3s", "description": "The following is the state transition table for a Moore state machine with one input, one output, and four states. Implement this state machine. Include a synchronous active high reset that resets the FSM to state A. \n// State | Next state in=0, Next state in=1 | Output\n// A | A, B | 0\n// B | C, B | 0\n// C | A, D | 0\n// D | C, B | 1", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput out\n);\n parameter A = 2'b00; \n parameter B = 2'b01; \n parameter C = 2'b10; \n parameter D = 2'b11; \n\n reg [1:0] state, next_state; \n reg out_reg; \n\n always @ (posedge clk) begin\n if (reset) begin\n state <= A;\n out_reg <= 0;\n end\n else begin\n state <= next_state;\n out_reg <= out;\n end\n end\n\n always @ (state, in) begin\n case (state)\n A: begin\n if (in) begin\n next_state = B;\n out = 0;\n end\n else begin\n next_state = A;\n out = 0;\n end\n end\n B: begin\n if (in) begin\n next_state = B;\n out = 0;\n end\n else begin\n next_state = C;\n out = 0;\n end\n end\n C: begin\n if (in) begin\n next_state = D;\n out = 0;\n end\n else begin\n next_state = A;\n out = 0;\n end\n end\n D: begin\n if (in) begin\n next_state = B;\n out = 1;\n end\n else begin\n next_state = C;\n out = 0;\n end\n end\n endcase\n end\n\n assign out = out_reg;\n\nendmodule", "error": "61: error: 'out' is not a valid l-value for a procedural assignment.\n5: : 'out' is declared here as a wire.\n65: error: 'out' is not a valid l-value for a procedural assignment.\n35: error: 'out' is not a valid l-value for a procedural assignment.\n51: error: 'out' is not a valid l-value for a procedural assignment.\n55: error: 'out' is not a valid l-value for a procedural assignment.\n31: error: 'out' is not a valid l-value for a procedural assignment.\n45: error: 'out' is not a valid l-value for a procedural assignment.\n41: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm_hdlc", "description": "Synchronous HDLC framing involves decoding a continuous bit stream of data to look for bit patterns that indicate the beginning and end of frames (packets). Seeing exactly 6 consecutive 1s (i.e., 01111110) is a \"flag\" that indicate frame boundaries. To avoid the data stream from accidentally containing \"flags\", the sender inserts a zero after every 5 consecutive 1s which the receiver must detect and discard. We also need to signal an error if there are 7 or more consecutive 1s. Create a Moore-type finite state machine to recognize these three sequences:\n\n// (1) 0111110: Signal a bit needs to be discarded (disc).\n// (2) 01111110: Flag the beginning/end of a frame (flag).\n// (3) 01111111...: Error (7 or more 1s) (err).\n\n// When the FSM is reset, it should be in a state that behaves as though the previous input were 0. The reset signal is active high synchronous. The output signals should be asserted for a complete cycle beginning on the clock cycle after the condition occurs.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput in,\n\toutput disc,\n\toutput flag,\n\toutput err);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput in,\n\toutput disc,\n\toutput flag,\n\toutput err);\n // Define the 3 states\n parameter s0 = 2'b00;\n parameter s1 = 2'b01;\n parameter s2 = 2'b10;\n\n // Define the state and output register\n reg [1:0] state, next_state;\n reg disc, flag, err;\n\n // Initialize the state and output register\n initial begin\n state = s0;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end\n\n // Update the state and output register on the clock cycle after the condition occurs\n always @(posedge clk) begin\n if (reset) begin\n state <= s0;\n disc <= 1'b0;\n flag <= 1'b0;\n err <= 1'b0;\n end else begin\n state <= next_state;\n disc <= 1'b0;\n flag <= 1'b0;\n err <= 1'b0;\n end\n end\n\n // Define the next state and output register based on the current state and input\n always @(*) begin\n case (state)\n s0: begin\n if (in == 1'b1) begin\n next_state = s1;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end else begin\n next_state = s0;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end\n end\n s1: begin\n if (in == 1'b1) begin\n next_state = s2;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end else begin\n next_state = s0;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end\n end\n s2: begin\n if (in == 1'b1) begin\n next_state = s2;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end else begin\n next_state = s0;\n disc = 1'b0;\n flag = 1'b1;\n err = 1'b0;\n end\n end\n default: begin\n next_state = s0;\n disc = 1'b0;\n flag = 1'b0;\n err = 1'b0;\n end\n endcase\n end\n\n endmodule", "error": "15: error: 'err' has already been declared in this scope.\n5: : It was declared here as a net.\n15: error: 'disc' has already been declared in this scope.\n15: error: 'flag' has already been declared in this scope.\n7: : It was declared here as a net.\n6: : It was declared here as a net.\n"} {"task_id": "fsm_hdlc", "description": "Synchronous HDLC framing involves decoding a continuous bit stream of data to look for bit patterns that indicate the beginning and end of frames (packets). Seeing exactly 6 consecutive 1s (i.e., 01111110) is a \"flag\" that indicate frame boundaries. To avoid the data stream from accidentally containing \"flags\", the sender inserts a zero after every 5 consecutive 1s which the receiver must detect and discard. We also need to signal an error if there are 7 or more consecutive 1s. Create a Moore-type finite state machine to recognize these three sequences:\n\n// (1) 0111110: Signal a bit needs to be discarded (disc).\n// (2) 01111110: Flag the beginning/end of a frame (flag).\n// (3) 01111111...: Error (7 or more 1s) (err).\n\n// When the FSM is reset, it should be in a state that behaves as though the previous input were 0. The reset signal is active high synchronous. The output signals should be asserted for a complete cycle beginning on the clock cycle after the condition occurs.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput in,\n\toutput disc,\n\toutput flag,\n\toutput err);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput in,\n\toutput disc,\n\toutput flag,\n\toutput err);\n parameter STATE_0 = 0;\n parameter STATE_1 = 1;\n parameter STATE_2 = 2;\n parameter STATE_3 = 3;\n parameter STATE_4 = 4;\n parameter STATE_5 = 5;\n parameter STATE_6 = 6;\n parameter STATE_DISCARD = 7;\n parameter STATE_ERROR = 8;\n\n reg [3:0] state;\n reg [3:0] next_state;\n\n reg disc_reg;\n reg flag_reg;\n reg err_reg;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= STATE_0;\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end else begin\n state <= next_state;\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n end\n\n always @(*) begin\n case (state)\n STATE_0: begin\n if (in == 1) begin\n next_state = STATE_1;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_1: begin\n if (in == 1) begin\n next_state = STATE_2;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_2: begin\n if (in == 1) begin\n next_state = STATE_3;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_3: begin\n if (in == 1) begin\n next_state = STATE_4;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_4: begin\n if (in == 1) begin\n next_state = STATE_5;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_5: begin\n if (in == 1) begin\n next_state = STATE_6;\n end else begin\n next_state = STATE_DISCARD;\n end\n end\n STATE_6: begin\n if (in == 1) begin\n next_state = STATE_6;\n end else begin\n next_state = STATE_0;\n end\n end\n STATE_DISCARD: begin\n next_state = STATE_0;\n disc_reg = 1;\n end\n STATE_ERROR: begin\n next_state = STATE_ERROR;\n err_reg = 1;\n end\n endcase\n end\n\n always @(posedge clk) begin\n if (reset) begin\n disc <= 0;\n flag <= 0;\n err <= 0;\n end else begin\n disc <= disc_reg;\n flag <= flag_reg;\n err <= err_reg;\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end else begin\n case (state)\n STATE_0: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_1: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_2: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_3: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_4: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_5: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_6: begin\n disc_reg <= 0;\n flag_reg <= 1;\n err_reg <= 0;\n end\n STATE_DISCARD: begin\n disc_reg <= 1;\n flag_reg <= 0;\n err_reg <= 0;\n end\n STATE_ERROR: begin\n disc_reg <= 0;\n flag_reg <= 0;\n err_reg <= 1;\n end\n endcase\n end\n end\n\n endmodule", "error": "109: error: 'err' is not a valid l-value for a procedural assignment.\n6: : 'flag' is declared here as a wire.\n108: error: 'flag' is not a valid l-value for a procedural assignment.\n104: error: 'flag' is not a valid l-value for a procedural assignment.\n7: : 'err' is declared here as a wire.\n5: : 'disc' is declared here as a wire.\n107: error: 'disc' is not a valid l-value for a procedural assignment.\n105: error: 'err' is not a valid l-value for a procedural assignment.\n103: error: 'disc' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm_onehot", "description": "Given the follow state machine with 1 input and 2 outputs (the outputs are given as \"(out1, out2)\"):\n\n// S0 (0, 0) --0--> S0\n// S0 (0, 0) --1--> S1\n// S1 (0, 0) --0--> S0\n// S1 (0, 0) --1--> S2\n// S2 (0, 0) --0--> S0\n// S2 (0, 0) --1--> S3\n// S3 (0, 0) --0--> S0\n// S3 (0, 0) --1--> S4\n// S4 (0, 0) --0--> S0\n// S4 (0, 0) --1--> S5\n// S5 (0, 0) --0--> S8\n// S5 (0, 0) --1--> S6\n// S6 (0, 0) --0--> S9\n// S6 (0, 0) --1--> S7\n// S7 (0, 1) --0--> S0\n// S7 (0, 1) --1--> S7\n// S8 (1, 0) --0--> S0\n// S8 (1, 0) --1--> S1\n// S9 (1, 1) --0--> S0\n// S9 (1, 1) --1--> S1\n\n// Suppose this state machine uses one-hot encoding, where state[0] through state[9] correspond to the states S0 though S9, respectively. The outputs are zero unless otherwise specified.\n\n// Write Verilog implementing the state transition logic and output logic portions of the state machine (but not the state flip-flops). You are given the current state in state[9:0] and must produce next_state[9:0] and the two outputs. Derive the logic equations by inspection assuming a one-hot encoding.", "module_header": "module top_module (\n\tinput in,\n\tinput [9:0] state,\n\toutput [9:0] next_state,\n\toutput out1,\n\toutput out2);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [9:0] state,\n\toutput [9:0] next_state,\n\toutput out1,\n\toutput out2);\n // Define the output logic\n\tassign out1 = (state[0] | state[2] | state[4] | state[6] | state[8]) ? 1'b0 : 1'b1;\n\tassign out2 = (state[0] | state[1] | state[3] | state[5] | state[7] | state[9]) ? 1'b0 : 1'b1;\n\n // Define the state transition logic\n\talways @* begin\n\t\tcase (state)\n\t\t\t10'b0000000001: next_state = (in) ? 10'b0000000010 : 10'b0000000001;\n\t\t\t10'b0000000010: next_state = (in) ? 10'b0000000100 : 10'b0000000001;\n\t\t\t10'b0000000100: next_state = (in) ? 10'b0000001000 : 10'b0000000001;\n\t\t\t10'b0000001000: next_state = (in) ? 10'b0000010000 : 10'b0000000001;\n\t\t\t10'b0000010000: next_state = (in) ? 10'b0000100000 : 10'b0000000001;\n\t\t\t10'b0000100000: next_state = (in) ? 10'b0001000000 : 10'b0000000001;\n\t\t\t10'b0001000000: next_state = (in) ? 10'b0010000000 : 10'b0000000001;\n\t\t\t10'b0010000000: next_state = (in) ? 10'b0100000000 : 10'b0000000001;\n\t\t\t10'b0100000000: next_state = (in) ? 10'b1000000000 : 10'b0000000001;\n\t\t\t10'b1000000000: next_state = (in) ? 10'b0000000001 : 10'b0000000001;\n\t\t\tdefault: next_state = 10'b0000000001;\n\t\tendcase\n\tend\n\n\tendmodule", "error": "18: error: 'next_state' is not a valid l-value for a procedural assignment.\n4: : 'next_state' is declared here as a wire.\n22: error: 'next_state' is not a valid l-value for a procedural assignment.\n23: error: 'next_state' is not a valid l-value for a procedural assignment.\n21: error: 'next_state' is not a valid l-value for a procedural assignment.\n15: error: 'next_state' is not a valid l-value for a procedural assignment.\n16: error: 'next_state' is not a valid l-value for a procedural assignment.\n24: error: 'next_state' is not a valid l-value for a procedural assignment.\n19: error: 'next_state' is not a valid l-value for a procedural assignment.\n17: error: 'next_state' is not a valid l-value for a procedural assignment.\n14: error: 'next_state' is not a valid l-value for a procedural assignment.\n20: error: 'next_state' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm_onehot", "description": "Given the follow state machine with 1 input and 2 outputs (the outputs are given as \"(out1, out2)\"):\n\n// S0 (0, 0) --0--> S0\n// S0 (0, 0) --1--> S1\n// S1 (0, 0) --0--> S0\n// S1 (0, 0) --1--> S2\n// S2 (0, 0) --0--> S0\n// S2 (0, 0) --1--> S3\n// S3 (0, 0) --0--> S0\n// S3 (0, 0) --1--> S4\n// S4 (0, 0) --0--> S0\n// S4 (0, 0) --1--> S5\n// S5 (0, 0) --0--> S8\n// S5 (0, 0) --1--> S6\n// S6 (0, 0) --0--> S9\n// S6 (0, 0) --1--> S7\n// S7 (0, 1) --0--> S0\n// S7 (0, 1) --1--> S7\n// S8 (1, 0) --0--> S0\n// S8 (1, 0) --1--> S1\n// S9 (1, 1) --0--> S0\n// S9 (1, 1) --1--> S1\n\n// Suppose this state machine uses one-hot encoding, where state[0] through state[9] correspond to the states S0 though S9, respectively. The outputs are zero unless otherwise specified.\n\n// Write Verilog implementing the state transition logic and output logic portions of the state machine (but not the state flip-flops). You are given the current state in state[9:0] and must produce next_state[9:0] and the two outputs. Derive the logic equations by inspection assuming a one-hot encoding.", "module_header": "module top_module (\n\tinput in,\n\tinput [9:0] state,\n\toutput [9:0] next_state,\n\toutput out1,\n\toutput out2);\n", "original_code": "module top_module (\n\tinput in,\n\tinput [9:0] state,\n\toutput [9:0] next_state,\n\toutput out1,\n\toutput out2);\n // Output logic\n assign out1 = (state[7] | state[8] | state[9]);\n assign out2 = (state[7] | state[8]);\n\n // Transition logic\n always @* begin\n next_state = 10'b0000000000;\n case (state)\n 10'b0000000001: if (in) next_state[1] = 1;\n 10'b0000000010: if (in) next_state[2] = 1;\n 10'b0000000100: if (in) next_state[4] = 1;\n 10'b0000001000: if (in) next_state[8] = 1;\n 10'b0000010000: if (in) next_state[9] = 1;\n 10'b0000100000: if (in) next_state[0] = 1;\n 10'b0001000000: if (in) next_state[1] = 1;\n 10'b0010000000: if (in) next_state[2] = 1;\n 10'b0100000000: if (in) next_state[4] = 1;\n 10'b1000000000: if (in) next_state[8] = 1;\n endcase\n end\n\nendmodule", "error": "4: : 'next_state['sd1]' is declared here as a wire.\n15: error: 'next_state['sd1]' is not a valid l-value for a procedural assignment.\n4: : 'next_state['sd2]' is declared here as a wire.\n4: : 'next_state['sd4]' is declared here as a wire.\n20: error: 'next_state['sd0]' is not a valid l-value for a procedural assignment.\n17: error: 'next_state['sd4]' is not a valid l-value for a procedural assignment.\n23: error: 'next_state['sd4]' is not a valid l-value for a procedural assignment.\n4: : 'next_state' is declared here as a wire.\n18: error: 'next_state['sd8]' is not a valid l-value for a procedural assignment.\n21: error: 'next_state['sd1]' is not a valid l-value for a procedural assignment.\n22: error: 'next_state['sd2]' is not a valid l-value for a procedural assignment.\n13: error: 'next_state' is not a valid l-value for a procedural assignment.\n4: : 'next_state['sd8]' is declared here as a wire.\n4: : 'next_state['sd0]' is declared here as a wire.\n4: : 'next_state['sd9]' is declared here as a wire.\n19: error: 'next_state['sd9]' is not a valid l-value for a procedural assignment.\n16: error: 'next_state['sd2]' is not a valid l-value for a procedural assignment.\n24: error: 'next_state['sd8]' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm_ps2", "description": "The PS/2 mouse protocol sends messages that are three bytes long. However, within a continuous byte stream, it's not obvious where messages start and end. The only indication is that the first byte of each three byte message always has in[3]=1 (but in[3] of the other two bytes may be 1 or 0 depending on data). We want a finite state machine that will search for message boundaries when given an input byte stream. The algorithm we'll use is to discard bytes until we see one with in[3]=1. We then assume that this is byte 1 of a message, and signal the receipt of a message once all 3 bytes have been received (done). The FSM should signal done in the cycle immediately after the third byte of each message was successfully received. Reset should be active high synchronous.", "module_header": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput done\n);\n //parameter declarations\n parameter S0 = 2'd0, S1 = 2'd1;\n //internal variable declarations\n reg [1:0] state;\n reg [1:0] nextstate;\n reg [1:0] flag = 2'd0;\n //sequential logic\n always @( posedge clk ) begin\n if ( reset == 1'b1 ) begin\n state <= S0;\n flag <= 2'd0;\n end else begin\n state <= nextstate;\n if(state == S1) begin\n flag <= flag + 1;\n end\n else if (state == S0) begin\n flag <= 2'd0;\n end\n end\n end\n //combinational logic\n always @( * ) begin\n nextstate = S0;\n case(state)\n S0: begin\n if(in[3] == 1) begin\n nextstate = S1;\n end\n end\n S1: begin\n if(in[3] == 0) begin\n nextstate = S2;\n end\n else begin \n nextstate = S0;\n end\n end\n S2: begin\n if(in[3] == 0) begin\n nextstate = S0;\n end\n else begin \n nextstate = S1;\n end\n end\n endcase\n //output logic\n case(flag)\n //do nothing\n 2'd0: done <= 0;\n //signal done in cycle after 2nd byte\n 2'd1: done <= 0;\n //signal done in cycle after 3rd byte\n 2'd2: done <= 1;\n endcase\n end\nendmodule", "error": "59: error: 'done' is not a valid l-value for a procedural assignment.\n39: error: Unable to bind wire/reg/memory `S2' in `top_module'\n5: : 'done' is declared here as a wire.\n45: error: Unable to bind wire/reg/memory `S2' in `top_module'\n61: error: 'done' is not a valid l-value for a procedural assignment.\n57: error: 'done' is not a valid l-value for a procedural assignment.\n"} {"task_id": "fsm_ps2", "description": "The PS/2 mouse protocol sends messages that are three bytes long. However, within a continuous byte stream, it's not obvious where messages start and end. The only indication is that the first byte of each three byte message always has in[3]=1 (but in[3] of the other two bytes may be 1 or 0 depending on data). We want a finite state machine that will search for message boundaries when given an input byte stream. The algorithm we'll use is to discard bytes until we see one with in[3]=1. We then assume that this is byte 1 of a message, and signal the receipt of a message once all 3 bytes have been received (done). The FSM should signal done in the cycle immediately after the third byte of each message was successfully received. Reset should be active high synchronous.", "module_header": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput done\n);\n parameter S0 = 2'b00, S1 = 2'b01, S2 = 2'b10, S3 = 2'b11;\n reg [1:0] state, next_state;\n reg done_r;\n wire [1:0] next_state;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= S0;\n done_r <= 1'b0;\n end else begin\n state <= next_state;\n done_r <= done;\n end\n end\n\n always @(*) begin\n case (state)\n S0: begin\n if (in[3] == 1'b1)\n next_state = S1;\n else\n next_state = S0;\n end\n S1: begin\n if (in[3] == 1'b0)\n next_state = S2;\n else\n next_state = S1;\n end\n S2: begin\n if (in[3] == 1'b0)\n next_state = S3;\n else\n next_state = S2;\n end\n S3: begin\n if (in[3] == 1'b0)\n next_state = S0;\n else\n next_state = S3;\n end\n endcase\n end\n\n assign done = (state == S3) ? done_r : 1'b0;\n\nendmodule", "error": "10: error: 'next_state' has already been declared in this scope.\n8: : It was declared here as a variable.\n"} {"task_id": "fsm_ps2data", "description": "We want a finite state machine that will search for message boundaries when given an input byte stream. The algorithm we'll use is to discard bytes until we see one with in[3]=1. We then assume that this is byte 1 of a message, and signal the receipt of a message once all 3 bytes have been received (done). The FSM should signal done in the cycle immediately after the third byte of each message was successfully received.\n\n// Implement the datapath module that will output the 24-bit (3 byte) message whenever a packet is received (out_bytes[23:16] is the first byte, out_bytes[15:8] is the second byte, etc.). The reset signal is active high synchronous. out_bytes needs to be valid whenever the done signal is asserted. You may output anything at other times (i.e., don't-care). \n\n// Waveform example:\n// time clk reset in[7:0] done out_bytes \n// 0ns 0 1 0 x x \n// 5ns 1 1 0 0 x \n// 10ns 0 1 0 0 x \n// 15ns 1 0 2c 0 x \n// 20ns 0 0 2c 0 x \n// 25ns 1 0 81 0 x \n// 30ns 0 0 81 0 x \n// 35ns 1 0 9 0 x \n// 40ns 0 0 9 0 x \n// 45ns 1 0 6b 1 2c8109 \n// 50ns 0 0 6b 1 2c8109 \n// 55ns 1 0 d 0 x \n// 60ns 0 0 d 0 x \n// 65ns 1 0 8d 0 x \n// 70ns 0 0 8d 0 x \n// 75ns 1 0 6d 1 6b0d8d \n// 80ns 0 0 6d 1 6b0d8d \n// 85ns 1 0 12 0 x \n// 90ns 0 0 12 0 x \n// 95ns 1 0 1 0 x \n// 100ns 0 0 1 0 x \n// 105ns 1 0 d 1 6d1201 \n// 110ns 0 0 d 1 6d1201 \n// 115ns 1 0 76 0 x \n// 120ns 0 0 76 0 x \n// 125ns 1 0 3d 0 x \n// 130ns 0 0 3d 0 x \n// 135ns 1 0 ed 1 d763d \n// 140ns 0 0 ed 1 d763d \n// 145ns 1 0 8c 0 x \n// 150ns 0 0 8c 0 x \n// 155ns 1 0 f9 0 x \n// 160ns 0 0 f9 0 x \n// 165ns 1 0 ce 1 ed8cf9 \n// 170ns 0 0 ce 1 ed8cf9 \n// 175ns 1 0 c5 0 x \n// 180ns 0 0 c5 0 x \n// 185ns 1 0 aa 0 x \n// 190ns 0 0 aa 0 x ", "module_header": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput [23:0] out_bytes,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput [23:0] out_bytes,\n\toutput done\n);\n // state definitions\n parameter s_start = 2'b00;\n parameter s_byte1 = 2'b01;\n parameter s_byte2 = 2'b10;\n parameter s_byte3 = 2'b11;\n\n // state register and next state logic\n reg [1:0] state, next_state;\n always @(posedge clk) begin\n if (reset) state <= s_start;\n else state <= next_state;\n end\n\n // state machine\n always @(*) begin\n case (state)\n s_start: next_state = in[3] ? s_byte1 : s_start;\n s_byte1: next_state = in[7] ? s_byte2 : s_start;\n s_byte2: next_state = in[3] ? s_byte3 : s_start;\n s_byte3: next_state = s_start;\n endcase\n end\n\n // output logic\n always @(*) begin\n case (state)\n s_start, s_byte1, s_byte2: done = 0;\n s_byte3: done = 1;\n endcase\n end\n\n // message byte register\n reg [23:0] out_bytes;\n always @(posedge clk) begin\n if (reset) out_bytes <= 0;\n else if (state == s_byte3) out_bytes <= {in[7:0], in[15:8], in[23:16]};\n end\n\nendmodule", "error": "40: error: 'out_bytes' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm_ps2data", "description": "We want a finite state machine that will search for message boundaries when given an input byte stream. The algorithm we'll use is to discard bytes until we see one with in[3]=1. We then assume that this is byte 1 of a message, and signal the receipt of a message once all 3 bytes have been received (done). The FSM should signal done in the cycle immediately after the third byte of each message was successfully received.\n\n// Implement the datapath module that will output the 24-bit (3 byte) message whenever a packet is received (out_bytes[23:16] is the first byte, out_bytes[15:8] is the second byte, etc.). The reset signal is active high synchronous. out_bytes needs to be valid whenever the done signal is asserted. You may output anything at other times (i.e., don't-care). \n\n// Waveform example:\n// time clk reset in[7:0] done out_bytes \n// 0ns 0 1 0 x x \n// 5ns 1 1 0 0 x \n// 10ns 0 1 0 0 x \n// 15ns 1 0 2c 0 x \n// 20ns 0 0 2c 0 x \n// 25ns 1 0 81 0 x \n// 30ns 0 0 81 0 x \n// 35ns 1 0 9 0 x \n// 40ns 0 0 9 0 x \n// 45ns 1 0 6b 1 2c8109 \n// 50ns 0 0 6b 1 2c8109 \n// 55ns 1 0 d 0 x \n// 60ns 0 0 d 0 x \n// 65ns 1 0 8d 0 x \n// 70ns 0 0 8d 0 x \n// 75ns 1 0 6d 1 6b0d8d \n// 80ns 0 0 6d 1 6b0d8d \n// 85ns 1 0 12 0 x \n// 90ns 0 0 12 0 x \n// 95ns 1 0 1 0 x \n// 100ns 0 0 1 0 x \n// 105ns 1 0 d 1 6d1201 \n// 110ns 0 0 d 1 6d1201 \n// 115ns 1 0 76 0 x \n// 120ns 0 0 76 0 x \n// 125ns 1 0 3d 0 x \n// 130ns 0 0 3d 0 x \n// 135ns 1 0 ed 1 d763d \n// 140ns 0 0 ed 1 d763d \n// 145ns 1 0 8c 0 x \n// 150ns 0 0 8c 0 x \n// 155ns 1 0 f9 0 x \n// 160ns 0 0 f9 0 x \n// 165ns 1 0 ce 1 ed8cf9 \n// 170ns 0 0 ce 1 ed8cf9 \n// 175ns 1 0 c5 0 x \n// 180ns 0 0 c5 0 x \n// 185ns 1 0 aa 0 x \n// 190ns 0 0 aa 0 x ", "module_header": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput [23:0] out_bytes,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput [7:0] in,\n\tinput reset,\n\toutput [23:0] out_bytes,\n\toutput done\n);\n parameter IDLE = 2'b00;\n parameter WAIT_FOR_START = 2'b01;\n parameter WAIT_FOR_END = 2'b10;\n\n reg [1:0] state;\n reg [23:0] out_bytes;\n reg done;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= IDLE;\n out_bytes <= 0;\n done <= 0;\n end else begin\n case (state)\n IDLE: begin\n if (in[3]) begin\n state <= WAIT_FOR_START;\n out_bytes <= {in, 8'b0};\n end\n end\n WAIT_FOR_START: begin\n if (in[3]) begin\n state <= WAIT_FOR_END;\n out_bytes <= {out_bytes[15:0], in, 8'b0};\n end else begin\n state <= WAIT_FOR_START;\n out_bytes <= {out_bytes[15:0], in, 8'b0};\n end\n end\n WAIT_FOR_END: begin\n if (in[3]) begin\n state <= WAIT_FOR_START;\n out_bytes <= {out_bytes[15:0], in, 8'b0};\n end else begin\n state <= IDLE;\n out_bytes <= {out_bytes[15:0], in, 8'b0};\n done <= 1;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "6: : It was declared here as a net.\n14: error: 'done' has already been declared in this scope.\n13: error: 'out_bytes' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm_serial", "description": "In many (older) serial communications protocols, each data byte is sent along with a start bit and a stop bit, to help the receiver delimit bytes from the stream of bits. One common scheme is to use one start bit (0), 8 data bits, and 1 stop bit (1). The line is also at logic 1 when nothing is being transmitted (idle). Design a finite state machine that will identify when bytes have been correctly received when given a stream of bits. It needs to identify the start bit, wait for all 8 data bits, then verify that the stop bit was correct. If the stop bit does not appear when expected, the FSM must wait until it finds a stop bit before attempting to receive the next byte. Include a active-high synchronous reset. Note that the serial protocol sends the least significant bit first.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput done\n);\n // Define the states of the FSM\n parameter IDLE = 2'b00;\n parameter START = 2'b01;\n parameter DATA = 2'b10;\n parameter STOP = 2'b11;\n\n // Define the state register and next state logic\n reg [1:0] state, next_state;\n always @ (posedge clk) begin\n if (reset) begin\n state <= IDLE;\n end else begin\n state <= next_state;\n end\n end\n\n // Define the output register and output logic\n reg done;\n always @ (state) begin\n case (state)\n IDLE: done = 0;\n START: done = 0;\n DATA: done = 0;\n STOP: done = 1;\n endcase\n end\n\n // Define the next state logic\n always @ (state, in) begin\n case (state)\n IDLE: begin\n if (in == 0) begin\n next_state = START;\n end else begin\n next_state = IDLE;\n end\n end\n START: begin\n if (in == 0) begin\n next_state = DATA;\n end else begin\n next_state = IDLE;\n end\n end\n DATA: begin\n if (in == 1) begin\n next_state = STOP;\n end else begin\n next_state = DATA;\n end\n end\n STOP: begin\n if (in == 1) begin\n next_state = IDLE;\n end else begin\n next_state = STOP;\n end\n end\n endcase\n end\n\nendmodule", "error": "24: error: 'done' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm_serial", "description": "In many (older) serial communications protocols, each data byte is sent along with a start bit and a stop bit, to help the receiver delimit bytes from the stream of bits. One common scheme is to use one start bit (0), 8 data bits, and 1 stop bit (1). The line is also at logic 1 when nothing is being transmitted (idle). Design a finite state machine that will identify when bytes have been correctly received when given a stream of bits. It needs to identify the start bit, wait for all 8 data bits, then verify that the stop bit was correct. If the stop bit does not appear when expected, the FSM must wait until it finds a stop bit before attempting to receive the next byte. Include a active-high synchronous reset. Note that the serial protocol sends the least significant bit first.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput done\n);\n // Define the states of the FSM\n parameter IDLE = 2'b00;\n parameter START = 2'b01;\n parameter DATA = 2'b10;\n parameter STOP = 2'b11;\n\n // Define the state register and next state logic\n reg [1:0] state, next_state;\n always @(posedge clk) begin\n if (reset) begin\n state <= IDLE;\n end else begin\n state <= next_state;\n end\n end\n\n // Define the output register and output logic\n reg done;\n always @(posedge clk) begin\n if (reset) begin\n done <= 0;\n end else begin\n done <= (state == STOP);\n end\n end\n\n // Define the state transition logic\n always @(*) begin\n case (state)\n IDLE: begin\n if (in == 0) begin\n next_state = START;\n end else begin\n next_state = IDLE;\n end\n end\n START: begin\n if (in == 0) begin\n next_state = START;\n end else begin\n next_state = DATA;\n end\n end\n DATA: begin\n if (in == 0) begin\n next_state = DATA;\n end else begin\n next_state = STOP;\n end\n end\n STOP: begin\n if (in == 1) begin\n next_state = IDLE;\n end else begin\n next_state = STOP;\n end\n end\n endcase\n end\n\nendmodule", "error": "24: error: 'done' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm_serialdata", "description": "In many (older) serial communications protocols, each data byte is sent along with a start bit and a stop bit, to help the receiver delimit bytes from the stream of bits. One common scheme is to use one start bit (0), 8 data bits, and 1 stop bit (1). The line is also at logic 1 when nothing is being transmitted (idle). Design a finite state machine that will identify when bytes have been correctly received when given a stream of bits. It needs to identify the start bit, wait for all 8 data bits, then verify that the stop bit was correct. The module will also output the correctly-received data byte. out_byte needs to be valid when done is 1, and is don't-care otherwise.If the stop bit does not appear when expected, the FSM must wait until it finds a stop bit before attempting to receive the next byte. Include a active-high synchronous reset. Note that the serial protocol sends the least significant bit first. It should assert done each time it finds a stop bit.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput [7:0] out_byte,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput [7:0] out_byte,\n\toutput done\n);\n // State Machine Code\n\n // States\n parameter IDLE = 2'b00;\n parameter START = 2'b01;\n parameter DATA = 2'b10;\n parameter STOP = 2'b11;\n\n // State Registers\n reg [1:0] state, next_state;\n\n // Output Registers\n reg [7:0] out_byte;\n reg done;\n\n // Bit Counter\n reg [3:0] bit_count;\n\n // Logic\n always @(posedge clk) begin\n\n if (reset) begin\n state <= IDLE;\n bit_count <= 4'b0;\n out_byte <= 8'b0;\n done <= 1'b0;\n end else begin\n state <= next_state;\n bit_count <= bit_count + 1;\n\n case (state)\n IDLE: begin\n if (in == 1'b0) begin\n next_state <= START;\n end else begin\n next_state <= IDLE;\n end\n end\n\n START: begin\n if (in == 1'b1) begin\n next_state <= STOP;\n bit_count <= 4'b0;\n out_byte <= 8'b0;\n end else begin\n next_state <= START;\n end\n end\n\n DATA: begin\n out_byte[7 - bit_count] <= in;\n if (bit_count == 4'b0000) begin\n next_state <= STOP;\n end else begin\n next_state <= DATA;\n end\n end\n\n STOP: begin\n if (in == 1'b1) begin\n next_state <= IDLE;\n done <= 1'b1;\n end else begin\n next_state <= STOP;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "6: : It was declared here as a net.\n20: error: 'out_byte' has already been declared in this scope.\n21: error: 'done' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "fsm_serialdata", "description": "In many (older) serial communications protocols, each data byte is sent along with a start bit and a stop bit, to help the receiver delimit bytes from the stream of bits. One common scheme is to use one start bit (0), 8 data bits, and 1 stop bit (1). The line is also at logic 1 when nothing is being transmitted (idle). Design a finite state machine that will identify when bytes have been correctly received when given a stream of bits. It needs to identify the start bit, wait for all 8 data bits, then verify that the stop bit was correct. The module will also output the correctly-received data byte. out_byte needs to be valid when done is 1, and is don't-care otherwise.If the stop bit does not appear when expected, the FSM must wait until it finds a stop bit before attempting to receive the next byte. Include a active-high synchronous reset. Note that the serial protocol sends the least significant bit first. It should assert done each time it finds a stop bit.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput [7:0] out_byte,\n\toutput done\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\tinput reset,\n\toutput [7:0] out_byte,\n\toutput done\n);\n // Your code here\n // Define the states\n parameter IDLE = 2'b00;\n parameter START = 2'b01;\n parameter DATA = 2'b10;\n parameter STOP = 2'b11;\n\n // Define the state register and next state logic\n reg [1:0] state, next_state;\n always @ (posedge clk) begin\n if (reset) begin\n state <= IDLE;\n end else begin\n state <= next_state;\n end\n end\n\n // Define the FSM output and next state logic\n reg [7:0] byte_reg;\n reg [3:0] bit_count;\n reg stop_detected;\n always @ (*) begin\n case (state)\n IDLE: begin\n if (in == 0) begin\n next_state = START;\n end else begin\n next_state = IDLE;\n end\n end\n START: begin\n if (in == 1) begin\n next_state = START;\n end else begin\n next_state = DATA;\n end\n end\n DATA: begin\n if (bit_count == 7) begin\n next_state = STOP;\n end else begin\n next_state = DATA;\n end\n end\n STOP: begin\n if (in == 1) begin\n next_state = IDLE;\n stop_detected = 1;\n end else begin\n next_state = STOP;\n end\n end\n endcase\n end\n\n // Define the output logic\n always @ (posedge clk) begin\n if (reset) begin\n byte_reg <= 0;\n bit_count <= 0;\n stop_detected <= 0;\n end else begin\n case (state)\n IDLE: begin\n byte_reg <= 0;\n bit_count <= 0;\n stop_detected <= 0;\n end\n START: begin\n byte_reg <= {in, byte_reg[7:1]};\n bit_count <= bit_count + 1;\n end\n DATA: begin\n byte_reg <= {in, byte_reg[7:1]};\n bit_count <= bit_count + 1;\n end\n STOP: begin\n if (stop_detected) begin\n out_byte <= byte_reg;\n done <= 1;\n end else begin\n out_byte <= 0;\n done <= 0;\n end\n byte_reg <= 0;\n bit_count <= 0;\n stop_detected <= 0;\n end\n endcase\n end\n end\n\n // Define the done signal\n always @ (posedge clk) begin\n if (reset) begin\n done <= 0;\n end else begin\n if (state == STOP) begin\n done <= 1;\n end else begin\n done <= 0;\n end\n end\n end\n\nendmodule", "error": "86: error: 'out_byte' is not a valid l-value for a procedural assignment.\n6: : 'done' is declared here as a wire.\n108: error: 'done' is not a valid l-value for a procedural assignment.\n106: error: 'done' is not a valid l-value for a procedural assignment.\n89: error: 'out_byte' is not a valid l-value for a procedural assignment.\n90: error: 'done' is not a valid l-value for a procedural assignment.\n87: error: 'done' is not a valid l-value for a procedural assignment.\n5: : 'out_byte' is declared here as a wire.\n103: error: 'done' is not a valid l-value for a procedural assignment.\n"} {"task_id": "gates", "description": "Build a combinational circuit with two inputs, a and b. There are 7 outputs, each with a logic gate driving it: \n// (1) out_and: a and b \n// (2) out_or: a or b \n// (3) out_xor: a xor b \n// (4) out_nand: a nand b \n// (5) out_nor: a nor b \n// (6) out_xnor: a xnor b \n// (7) out_anotb: a and-not b", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor,\n\toutput out_nand,\n\toutput out_nor,\n\toutput out_xnor,\n\toutput out_anotb\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor,\n\toutput out_nand,\n\toutput out_nor,\n\toutput out_xnor,\n\toutput out_anotb\n);\nalways @(a or b) begin\n\t out_and = a & b;\n\t out_or = a | b;\n\t out_xor = a ^ b;\n\t out_nand = ~(a & b);\n\t out_nor = ~(a | b);\n\t out_xnor = ~(a ^ b);\n\t out_anotb = a & ~b;\n end\n\nendmodule\n", "error": "7: : 'out_nand' is declared here as a wire.\n9: : 'out_xnor' is declared here as a wire.\n15: error: 'out_xor' is not a valid l-value for a procedural assignment.\n14: error: 'out_or' is not a valid l-value for a procedural assignment.\n4: : 'out_and' is declared here as a wire.\n13: error: 'out_and' is not a valid l-value for a procedural assignment.\n19: error: 'out_anotb' is not a valid l-value for a procedural assignment.\n5: : 'out_or' is declared here as a wire.\n16: error: 'out_nand' is not a valid l-value for a procedural assignment.\n18: error: 'out_xnor' is not a valid l-value for a procedural assignment.\n17: error: 'out_nor' is not a valid l-value for a procedural assignment.\n10: : 'out_anotb' is declared here as a wire.\n6: : 'out_xor' is declared here as a wire.\n8: : 'out_nor' is declared here as a wire.\n"} {"task_id": "gates100", "description": "Build a combinational circuit with 100 inputs, in[99:0]. There are 3 outputs: \n// (1) out_and: output of a 100-input AND gate. \n// (2) out_or: output of a 100-input OR gate. \n// (3) out_xor: output of a 100-input XOR gate.\n\n", "module_header": "module top_module (\n\tinput [99:0] in,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor\n);\n", "original_code": "module top_module (\n\tinput [99:0] in,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor\n);\n wire [99:0] and_gate_input;\n wire [99:0] or_gate_input;\n wire [99:0] xor_gate_input;\n assign and_gate_input = in;\n assign or_gate_input = in;\n assign xor_gate_input = in;\n and_gate and_gate_inst (.in(and_gate_input), .out(out_and));\n or_gate or_gate_inst (.in(or_gate_input), .out(out_or));\n xor_gate xor_gate_inst (.in(xor_gate_input), .out(out_xor));\n assign out_and = ∈\n assign out_or = |in;\n assign out_xor = ^in;\n assign out_and = (in == 100'b1) ? 1'b1 : 1'b0;\n assign out_or = (in != 100'b0) ? 1'b1 : 1'b0;\n assign out_xor = (in % 2 == 1) ? 1'b1 : 1'b0;\nendmodule", "error": "13: error: Unknown module type: and_gate\n15: error: Unknown module type: xor_gate\n14: error: Unknown module type: or_gate\n"} {"task_id": "gates4", "description": "Build a combinational circuit with four inputs, in[3:0]. There are 3 outputs: \n// (1) out_and: output of a 4-input AND gate. \n// (2) out_or: output of a 4-input OR gate. \n// (3) out_xor: output of a 4-input XOR gate.\n", "module_header": "module top_module (\n\tinput [3:0] in,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor\n);\n", "original_code": "module top_module (\n\tinput [3:0] in,\n\toutput out_and,\n\toutput out_or,\n\toutput out_xor\n);\nalways @(*) begin\n\tout_and = ∈\n\tout_or = |in;\n\tout_xor = ^in;\nend\n\nendmodule\n", "error": "10: error: 'out_xor' is not a valid l-value for a procedural assignment.\n5: : 'out_xor' is declared here as a wire.\n7: warning: @* found no sensitivities so it will never trigger.\n8: error: 'out_and' is not a valid l-value for a procedural assignment.\n9: error: 'out_or' is not a valid l-value for a procedural assignment.\n4: : 'out_or' is declared here as a wire.\n3: : 'out_and' is declared here as a wire.\n"} {"task_id": "gatesv", "description": "You are given a four-bit input vector in[3:0]. We want to know some relationships between each bit and its neighbour: \n// (1) out_both: Each bit of this output vector should indicate whether both the corresponding input bit and its neighbour to the left (higher index) are '1'. For example, out_both[2] should indicate if in[2] and in[3] are both 1. Since in[3] has no neighbour to the left, the answer is obvious so we don't need to know out_both[3]. \n// (2) out_any: Each bit of this output vector should indicate whether any of the corresponding input bit and its neighbour to the right are '1'. For example, out_any[2] should indicate if either in[2] or in[1] are 1. Since in[0] has no neighbour to the right, the answer is obvious so we don't need to know out_any[0]. \n// (3) out_different: Each bit of this output vector should indicate whether the corresponding input bit is different from its neighbour to the left. For example, out_different[2] should indicate if in[2] is different from in[3]. For this part, treat the vector as wrapping around, so in[3]'s neighbour to the left is in[0].", "module_header": "module top_module (\n\tinput [3:0] in,\n\toutput [2:0] out_both,\n\toutput [3:1] out_any,\n\toutput [3:0] out_different\n);\n", "original_code": "module top_module (\n\tinput [3:0] in,\n\toutput [2:0] out_both,\n\toutput [3:1] out_any,\n\toutput [3:0] out_different\n);\n // (1) out_both: Each bit of this output vector should indicate whether both the corresponding input bit and its neighbour to the left (higher index) are '1'.\n // Since in[3] has no neighbour to the left, the answer is obvious so we don't need to know out_both[3].\n // For other bits, we can calculate it using a bitwise AND operation.\n assign out_both[2] = in[2] & in[3];\n assign out_both[1] = in[1] & in[2];\n assign out_both[0] = in[0] & in[1];\n\n // (2) out_any: Each bit of this output vector should indicate whether any of the corresponding input bit and its neighbour to the right are '1'.\n // Since in[0] has no neighbour to the right, the answer is obvious so we don't need to know out_any[0].\n // For other bits, we can calculate it using a bitwise OR operation.\n assign out_any[3] = in[3] | in[2];\n assign out_any[2] = in[2] | in[1];\n assign out_any[1] = in[1] | in[0];\n assign out_any[0] = in[0] | in[3];\n\n // (3) out_different: Each bit of this output vector should indicate whether the corresponding input bit is different from its neighbour to the left.\n // For this part, treat the vector as wrapping around, so in[3]'s neighbour to the left is in[0].\n // We can calculate it using a bitwise XOR operation.\n assign out_different[3] = in[3] ^ in[0];\n assign out_different[2] = in[2] ^ in[3];\n assign out_different[1] = in[1] ^ in[2];\n assign out_different[0] = in[0] ^ in[1];\n\nendmodule", "error": "20: sorry: part selects straddling the start of signal (out_any['sd0]) are not currently supported.\n"} {"task_id": "gatesv", "description": "You are given a four-bit input vector in[3:0]. We want to know some relationships between each bit and its neighbour: \n// (1) out_both: Each bit of this output vector should indicate whether both the corresponding input bit and its neighbour to the left (higher index) are '1'. For example, out_both[2] should indicate if in[2] and in[3] are both 1. Since in[3] has no neighbour to the left, the answer is obvious so we don't need to know out_both[3]. \n// (2) out_any: Each bit of this output vector should indicate whether any of the corresponding input bit and its neighbour to the right are '1'. For example, out_any[2] should indicate if either in[2] or in[1] are 1. Since in[0] has no neighbour to the right, the answer is obvious so we don't need to know out_any[0]. \n// (3) out_different: Each bit of this output vector should indicate whether the corresponding input bit is different from its neighbour to the left. For example, out_different[2] should indicate if in[2] is different from in[3]. For this part, treat the vector as wrapping around, so in[3]'s neighbour to the left is in[0].", "module_header": "module top_module (\n\tinput [3:0] in,\n\toutput [2:0] out_both,\n\toutput [3:1] out_any,\n\toutput [3:0] out_different\n);\n", "original_code": "module top_module (\n\tinput [3:0] in,\n\toutput [2:0] out_both,\n\toutput [3:1] out_any,\n\toutput [3:0] out_different\n);\n // (1) out_both\n assign out_both0 = in0 & in1;\n assign out_both1 = in1 & in2;\n assign out_both2 = in2 & in3;\n\n // (2) out_any\n assign out_any0 = in0 | in1;\n assign out_any1 = in1 | in2;\n assign out_any2 = in2 | in3;\n assign out_any3 = in3 | in0;\n\n // (3) out_different\n assign out_different0 = in0 ^ in1;\n assign out_different1 = in1 ^ in2;\n assign out_different2 = in2 ^ in3;\n assign out_different3 = in3 ^ in0;\n\nendmodule", "error": "21: error: Unable to bind wire/reg/memory `in2' in `top_module'\n9: error: Unable to bind wire/reg/memory `in2' in `top_module'\n22: error: Unable to bind wire/reg/memory `in0' in `top_module'\n14: warning: implicit definition of wire 'out_any1'.\n8: error: Unable to elaborate r-value: (in0)&(in1)\n19: warning: implicit definition of wire 'out_different0'.\n14: error: Unable to bind wire/reg/memory `in1' in `top_module'\n20: error: Unable to elaborate r-value: (in1)^(in2)\n10: warning: implicit definition of wire 'out_both2'.\n16: error: Unable to elaborate r-value: (in3)|(in0)\n9: error: Unable to bind wire/reg/memory `in1' in `top_module'\n9: error: Unable to elaborate r-value: (in1)&(in2)\n13: error: Unable to bind wire/reg/memory `in0' in `top_module'\n10: error: Unable to bind wire/reg/memory `in2' in `top_module'\n14: error: Unable to elaborate r-value: (in1)|(in2)\n20: error: Unable to bind wire/reg/memory `in1' in `top_module'\n20: error: Unable to bind wire/reg/memory `in2' in `top_module'\n22: warning: implicit definition of wire 'out_different3'.\n21: error: Unable to bind wire/reg/memory `in3' in `top_module'\n15: error: Unable to bind wire/reg/memory `in3' in `top_module'\n8: error: Unable to bind wire/reg/memory `in1' in `top_module'\n22: error: Unable to elaborate r-value: (in3)^(in0)\n13: error: Unable to bind wire/reg/memory `in1' in `top_module'\n15: error: Unable to elaborate r-value: (in2)|(in3)\n21: error: Unable to elaborate r-value: (in2)^(in3)\n14: error: Unable to bind wire/reg/memory `in2' in `top_module'\n16: error: Unable to bind wire/reg/memory `in0' in `top_module'\n15: warning: implicit definition of wire 'out_any2'.\n19: error: Unable to elaborate r-value: (in0)^(in1)\n19: error: Unable to bind wire/reg/memory `in1' in `top_module'\n9: warning: implicit definition of wire 'out_both1'.\n22: error: Unable to bind wire/reg/memory `in3' in `top_module'\n19: error: Unable to bind wire/reg/memory `in0' in `top_module'\n16: warning: implicit definition of wire 'out_any3'.\n13: warning: implicit definition of wire 'out_any0'.\n21: warning: implicit definition of wire 'out_different2'.\n13: error: Unable to elaborate r-value: (in0)|(in1)\n20: warning: implicit definition of wire 'out_different1'.\n8: error: Unable to bind wire/reg/memory `in0' in `top_module'\n15: error: Unable to bind wire/reg/memory `in2' in `top_module'\n8: warning: implicit definition of wire 'out_both0'.\n16: error: Unable to bind wire/reg/memory `in3' in `top_module'\n10: error: Unable to elaborate r-value: (in2)&(in3)\n10: error: Unable to bind wire/reg/memory `in3' in `top_module'\n"} {"task_id": "gatesv100", "description": "You are given a 100-bit input vector in[99:0]. We want to know some relationships between each bit and its neighbour: \n// (1) out_both: Each bit of this output vector should indicate whether both the corresponding input bit and its neighbour to the left are '1'. For example, out_both[98] should indicate if in[98] and in[99] are both 1. Since in[99] has no neighbour to the left, the answer is obvious so we don't need to know out_both[99]. \n// (2) out_any: Each bit of this output vector should indicate whether any of the corresponding input bit and its neighbour to the right are '1'. For example, out_any[2] should indicate if either in[2] or in[1] are 1. Since in[0] has no neighbour to the right, the answer is obvious so we don't need to know out_any[0]. \n// (3) out_different: Each bit of this output vector should indicate whether the corresponding input bit is different from its neighbour to the left. For example, out_different[98] should indicate if in[98] is different from in[99]. For this part, treat the vector as wrapping around, so in[99]'s neighbour to the left is in[0].\n", "module_header": "module top_module (\n\tinput [99:0] in,\n\toutput [98:0] out_both,\n\toutput [99:1] out_any,\n\toutput [99:0] out_different\n);\n", "original_code": "module top_module (\n\tinput [99:0] in,\n\toutput [98:0] out_both,\n\toutput [99:1] out_any,\n\toutput [99:0] out_different\n);\n assign out_both = {in[99:1] & in[0:98]};\n assign out_any = {in[99:1] | in[0:98]};\n assign out_different = {in[99:1] ^ in[0:98]};\n\nendmodule", "error": "9: error: part select in[0:98] is out of order.\n8: error: part select in[0:98] is out of order.\n7: error: part select in[0:98] is out of order.\n"} {"task_id": "gatesv100", "description": "You are given a 100-bit input vector in[99:0]. We want to know some relationships between each bit and its neighbour: \n// (1) out_both: Each bit of this output vector should indicate whether both the corresponding input bit and its neighbour to the left are '1'. For example, out_both[98] should indicate if in[98] and in[99] are both 1. Since in[99] has no neighbour to the left, the answer is obvious so we don't need to know out_both[99]. \n// (2) out_any: Each bit of this output vector should indicate whether any of the corresponding input bit and its neighbour to the right are '1'. For example, out_any[2] should indicate if either in[2] or in[1] are 1. Since in[0] has no neighbour to the right, the answer is obvious so we don't need to know out_any[0]. \n// (3) out_different: Each bit of this output vector should indicate whether the corresponding input bit is different from its neighbour to the left. For example, out_different[98] should indicate if in[98] is different from in[99]. For this part, treat the vector as wrapping around, so in[99]'s neighbour to the left is in[0].\n", "module_header": "module top_module (\n\tinput [99:0] in,\n\toutput [98:0] out_both,\n\toutput [99:1] out_any,\n\toutput [99:0] out_different\n);\n", "original_code": "module top_module (\n\tinput [99:0] in,\n\toutput [98:0] out_both,\n\toutput [99:1] out_any,\n\toutput [99:0] out_different\n);\n assign out_both = {in[99] & in[0:98], in[0:98] & in[1:99]};\n assign out_any = {in[0] | in[1:99], in[1:99] | in[0:98]};\n assign out_different = {in[99] ^ in[0], in[0] ^ in[1:99]};\n\nendmodule", "error": "8: error: part select in[0:98] is out of order.\n7: internal error: NetEConcat input width = 200, expecting 198\n7: error: part select in[0:98] is out of order.\n9: internal error: NetEConcat input width = 101, expecting 100\n8: internal error: NetEConcat input width = 200, expecting 198\n8: error: part select in[1:99] is out of order.\n7: error: part select in[1:99] is out of order.\n9: error: part select in[1:99] is out of order.\n"} {"task_id": "gshare", "description": "Build a gshare branch predictor with 7-bit pc and 7-bit global history, hashed (using xor) into a 7-bit index. This index accesses a 128-entry table of two-bit saturating counters. The branch predictor should contain a 7-bit global branch history register. The branch predictor has two sets of interfaces: One for doing predictions and one for doing training. The prediction interface is used in the processor's Fetch stage to ask the branch predictor for branch direction predictions for the instructions being fetched. Once these branches proceed down the pipeline and are executed, the true outcomes of the branches become known. The branch predictor is then trained using the actual branch direction outcomes. \n// When a branch prediction is requested (predict_valid = 1) for a given pc, the branch predictor produces the predicted branch direction and state of the branch history register used to make the prediction. The branch history register is then updated (at the next positive clock edge) for the predicted branch. \n// When training for a branch is requested (train_valid = 1), the branch predictor is told the pc and branch history register value for the branch that is being trained, as well as the actual branch outcome and whether the branch was a misprediction (needing a pipeline flush). Update the pattern history table (PHT) to train the branch predictor to predict this branch more accurately next time. In addition, if the branch being trained is mispredicted, also recover the branch history register to the state immediately after the mispredicting branch completes execution.\n// If training for a misprediction and a prediction (for a different, younger instruction) occurs in the same cycle, both operations will want to modify the branch history register. When this happens, training takes precedence, because the branch being predicted will be discarded anyway. If training and prediction of the same PHT entry happen at the same time, the prediction sees the PHT state before training because training only modifies the PHT at the next positive clock edge. The following timing diagram shows the timing when training and predicting PHT entry 0 at the same time. The training request at cycle 4 changes the PHT entry state in cycle 5, but the prediction request in cycle 4 outputs the PHT state at cycle 4, without considering the effect of the training request in cycle 4. Reset is asynchronous active-high.", "module_header": "module top_module(\n\tinput clk,\n\tinput areset, \n\n\tinput predict_valid,\n\tinput [6:0] predict_pc,\n\toutput predict_taken, \n\toutput [6:0] predict_history,\n\n\tinput train_valid,\n\tinput train_taken,\n\tinput train_mispredicted,\n\tinput [6:0] train_history, \n\tinput [6:0] train_pc\n);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput areset, \n\n\tinput predict_valid,\n\tinput [6:0] predict_pc,\n\toutput predict_taken, \n\toutput [6:0] predict_history,\n\n\tinput train_valid,\n\tinput train_taken,\n\tinput train_mispredicted,\n\tinput [6:0] train_history, \n\tinput [6:0] train_pc\n);\n // Global Branch History Register\n reg [6:0] branch_history_reg;\n reg [6:0] branch_history_reg_next;\n\n always @(posedge clk) begin\n if (areset) begin\n branch_history_reg <= 7'b0;\n branch_history_reg_next <= 7'b0;\n end else begin\n branch_history_reg <= branch_history_reg_next;\n branch_history_reg_next <= (branch_history_reg << 1) | train_taken;\n end\n end\n\n // Pattern History Table\n reg [1:0] PHT [0:127];\n reg [1:0] PHT_next [0:127];\n\n always @(posedge clk) begin\n if (areset) begin\n PHT <= {128{2'b01}};\n PHT_next <= {128{2'b01}};\n end else begin\n PHT <= PHT_next;\n PHT_next <= PHT;\n end\n end\n\n always @(*) begin\n if (train_valid) begin\n PHT_next[train_pc][1] = train_taken;\n end else begin\n PHT_next[predict_pc][1] = PHT[predict_pc][1];\n end\n end\n\n // Prediction Output\n assign predict_taken = PHT[predict_pc][1] ^ branch_history_reg[6];\n assign predict_history = branch_history_reg;\n\n // Training Input\n always @(posedge clk) begin\n if (train_valid && train_mispredicted) begin\n branch_history_reg_next <= branch_history_reg;\n end else begin\n branch_history_reg_next <= branch_history_reg;\n end\n end\n\nendmodule", "error": "37: internal error: I don't know how to elaborate(ivl_type_t) this expression: {'sd128{2'd1}}\n39: error: the type of the variable 'PHT_next' doesn't match the context type.\n40: : context type=11netuarray_t\n36: internal error: I don't know how to elaborate(ivl_type_t) this expression: {'sd128{2'd1}}\n40: error: the type of the variable 'PHT' doesn't match the context type.\n39: : context type=11netuarray_t\n39: : variable type=netvector_t:logic unsigned[1:0]\n48: warning: @* is sensitive to all 128 words in array 'PHT'.\n40: : variable type=netvector_t:logic unsigned[1:0]\n"} {"task_id": "gshare", "description": "Build a gshare branch predictor with 7-bit pc and 7-bit global history, hashed (using xor) into a 7-bit index. This index accesses a 128-entry table of two-bit saturating counters. The branch predictor should contain a 7-bit global branch history register. The branch predictor has two sets of interfaces: One for doing predictions and one for doing training. The prediction interface is used in the processor's Fetch stage to ask the branch predictor for branch direction predictions for the instructions being fetched. Once these branches proceed down the pipeline and are executed, the true outcomes of the branches become known. The branch predictor is then trained using the actual branch direction outcomes. \n// When a branch prediction is requested (predict_valid = 1) for a given pc, the branch predictor produces the predicted branch direction and state of the branch history register used to make the prediction. The branch history register is then updated (at the next positive clock edge) for the predicted branch. \n// When training for a branch is requested (train_valid = 1), the branch predictor is told the pc and branch history register value for the branch that is being trained, as well as the actual branch outcome and whether the branch was a misprediction (needing a pipeline flush). Update the pattern history table (PHT) to train the branch predictor to predict this branch more accurately next time. In addition, if the branch being trained is mispredicted, also recover the branch history register to the state immediately after the mispredicting branch completes execution.\n// If training for a misprediction and a prediction (for a different, younger instruction) occurs in the same cycle, both operations will want to modify the branch history register. When this happens, training takes precedence, because the branch being predicted will be discarded anyway. If training and prediction of the same PHT entry happen at the same time, the prediction sees the PHT state before training because training only modifies the PHT at the next positive clock edge. The following timing diagram shows the timing when training and predicting PHT entry 0 at the same time. The training request at cycle 4 changes the PHT entry state in cycle 5, but the prediction request in cycle 4 outputs the PHT state at cycle 4, without considering the effect of the training request in cycle 4. Reset is asynchronous active-high.", "module_header": "module top_module(\n\tinput clk,\n\tinput areset, \n\n\tinput predict_valid,\n\tinput [6:0] predict_pc,\n\toutput predict_taken, \n\toutput [6:0] predict_history,\n\n\tinput train_valid,\n\tinput train_taken,\n\tinput train_mispredicted,\n\tinput [6:0] train_history, \n\tinput [6:0] train_pc\n);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput areset, \n\n\tinput predict_valid,\n\tinput [6:0] predict_pc,\n\toutput predict_taken, \n\toutput [6:0] predict_history,\n\n\tinput train_valid,\n\tinput train_taken,\n\tinput train_mispredicted,\n\tinput [6:0] train_history, \n\tinput [6:0] train_pc\n);\n parameter PHT_SIZE = 128;\n parameter PHT_ENTRY_SIZE = 2;\n parameter PHT_INDEX_SIZE = 7;\n parameter GHR_SIZE = 7;\n\n reg [PHT_ENTRY_SIZE-1:0] pht [PHT_SIZE-1:0];\n reg [GHR_SIZE-1:0] ghr;\n reg [PHT_INDEX_SIZE-1:0] pht_index;\n\n assign predict_taken = pht[pht_index][0];\n assign predict_history = ghr;\n\n always @(posedge clk) begin\n if (areset) begin\n ghr <= 0;\n pht <= 0;\n end else begin\n if (train_valid) begin\n if (train_mispredicted) begin\n ghr <= train_history;\n end else begin\n pht[pht_index] <= pht[pht_index] + train_taken;\n end\n end\n if (predict_valid) begin\n pht_index <= predict_pc ^ ghr;\n ghr <= {ghr[GHR_SIZE-2:0], predict_taken};\n end\n end\n end\n\nendmodule", "error": "31: error: The expression ''sd0' cannot be implicitly cast to the target type.\n"} {"task_id": "hadd", "description": "Create a half adder. A half adder adds two bits (with no carry-in) and produces a sum and carry-out.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\toutput sum,\n\toutput cout\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\toutput sum,\n\toutput cout\n);\n always @ (a, b) begin\n sum = a ^ b;\n cout = a & b;\n end\n\nendmodule", "error": "4: : 'sum' is declared here as a wire.\n5: : 'cout' is declared here as a wire.\n9: error: 'cout' is not a valid l-value for a procedural assignment.\n8: error: 'sum' is not a valid l-value for a procedural assignment.\n"} {"task_id": "hadd", "description": "Create a half adder. A half adder adds two bits (with no carry-in) and produces a sum and carry-out.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\toutput sum,\n\toutput cout\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\toutput sum,\n\toutput cout\n);\n half_adder ha(a, b, sum, cout);\n\nendmodule", "error": "7: error: Unknown module type: half_adder\n"} {"task_id": "history_shift", "description": "Build a 32-bit global history shift register, including support for rolling back state in response to a pipeline flush caused by a branch misprediction. When a branch prediction is made (predict_valid = 1), shift in predict_taken from the LSB side to update the branch history for the predicted branch. (predict_history[0] is the direction of the youngest branch.) When a branch misprediction occurs (train_mispredicted = 1), load the branch history register with the history after the completion of the mispredicted branch. This is the history before the mispredicted branch (train_history) concatenated with the actual result of the branch (train_taken). If both a prediction and misprediction occur at the same time, the misprediction takes precedence, because the pipeline flush will also flush out the branch that is currently making a prediction. predict_history is the value of the branch history register. areset is a positive edge triggered asynchronous reset that resets the history counter to zero.\n\n", "module_header": "module top_module\n(\n input clk,\n input areset,\n input predict_valid,\n input predict_taken,\n output logic [31:0] predict_history,\n \n input train_mispredicted,\n input train_taken,\n input [31:0] train_history\n);\n", "original_code": "module top_module\n(\n input clk,\n input areset,\n input predict_valid,\n input predict_taken,\n output logic [31:0] predict_history,\n \n input train_mispredicted,\n input train_taken,\n input [31:0] train_history\n);\n logic [31:0] ghr_next;\n \n always_comb begin\n ghr_next = ghr;\n if (predict_valid) begin\n ghr_next[0] = predict_taken;\n ghr_next[1:31] = ghr[0:30];\n end else if (train_mispredicted) begin\n ghr_next = train_history | train_taken;\n end\n end\n \n always_ff @(posedge clk, posedge areset) begin\n if (areset) begin\n ghr <= 0;\n end else begin\n ghr <= ghr_next;\n end\n end\n\n assign predict_history = ghr;\n\nendmodule", "error": "33: error: Unable to elaborate r-value: ghr\n29: error: Could not find variable ``ghr'' in ``top_module''\n33: error: Unable to bind wire/reg/memory `ghr' in `top_module'\n27: error: Could not find variable ``ghr'' in ``top_module''\n19: error: part select ghr_next[1:31] is reversed.\n16: error: Unable to bind wire/reg/memory `ghr' in `top_module'\n19: error: Unable to bind wire/reg/memory `ghr['sd0:'sd30]' in `top_module'\n"} {"task_id": "history_shift", "description": "Build a 32-bit global history shift register, including support for rolling back state in response to a pipeline flush caused by a branch misprediction. When a branch prediction is made (predict_valid = 1), shift in predict_taken from the LSB side to update the branch history for the predicted branch. (predict_history[0] is the direction of the youngest branch.) When a branch misprediction occurs (train_mispredicted = 1), load the branch history register with the history after the completion of the mispredicted branch. This is the history before the mispredicted branch (train_history) concatenated with the actual result of the branch (train_taken). If both a prediction and misprediction occur at the same time, the misprediction takes precedence, because the pipeline flush will also flush out the branch that is currently making a prediction. predict_history is the value of the branch history register. areset is a positive edge triggered asynchronous reset that resets the history counter to zero.\n\n", "module_header": "module top_module\n(\n input clk,\n input areset,\n input predict_valid,\n input predict_taken,\n output logic [31:0] predict_history,\n \n input train_mispredicted,\n input train_taken,\n input [31:0] train_history\n);\n", "original_code": "module top_module\n(\n input clk,\n input areset,\n input predict_valid,\n input predict_taken,\n output logic [31:0] predict_history,\n \n input train_mispredicted,\n input train_taken,\n input [31:0] train_history\n);\n\n always_comb begin\n if (train_mispredicted) begin\n predict_history = {train_history, train_taken};\n end\n else if (predict_valid) begin\n predict_history = {predict_history[30:0], predict_taken};\n end\n else begin\n predict_history = predict_history;\n end\n end\n \n always_ff @(posedge clk) begin\n if (areset) begin\n predict_history <= 0;\n end\n else begin\n predict_history <= predict_history;\n end\n end\n \nendmodule", "error": "14: sorry: constant selects in always_* processes are not currently supported (all bits will be included).\n"} {"task_id": "kmap2", "description": "Implement the circuit described by the Karnaugh map below.\n\n// ab\n// cd 00 01 11 10\n// 00 | 1 | 1 | 0 | 1 |\n// 01 | 1 | 0 | 0 | 1 |\n// 11 | 0 | 1 | 1 | 1 |\n// 10 | 1 | 1 | 0 | 0 |", "module_header": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out\n);\n // Declare variables\n wire w1, w2, w3, w4, w5, w6, w7, w8;\n\n // Implement Boolean functions\n assign w1 = ~(a & b & ~c & ~d);\n assign w2 = ~(a & ~b & ~c & ~d);\n assign w3 = ~(a & b & c & ~d);\n assign w4 = ~(a & ~b & c & ~d);\n assign w5 = ~(a & b & ~c & d);\n assign w6 = ~(a & ~b & c & d);\n assign w7 = ~(a & b & c & d);\n assign w8 = ~(a & ~b & ~c & d);\n\n // Implement Karnaugh map using case statement\n always @(*) begin\n case ({a, b, c, d})\n 4'b0000: out = 1;\n 4'b0001: out = 1;\n 4'b0010: out = 0;\n 4'b0100: out = 1;\n 4'b1000: out = 0;\n 4'b0011: out = 1;\n 4'b0110: out = 0;\n 4'b1001: out = 1;\n 4'b1011: out = 0;\n 4'b1100: out = 1;\n 4'b1101: out = 0;\n default: out = 0;\n endcase\n end\n\nendmodule", "error": "30: error: 'out' is not a valid l-value for a procedural assignment.\n33: error: 'out' is not a valid l-value for a procedural assignment.\n28: error: 'out' is not a valid l-value for a procedural assignment.\n34: error: 'out' is not a valid l-value for a procedural assignment.\n26: error: 'out' is not a valid l-value for a procedural assignment.\n35: error: 'out' is not a valid l-value for a procedural assignment.\n25: error: 'out' is not a valid l-value for a procedural assignment.\n27: error: 'out' is not a valid l-value for a procedural assignment.\n24: error: 'out' is not a valid l-value for a procedural assignment.\n29: error: 'out' is not a valid l-value for a procedural assignment.\n31: error: 'out' is not a valid l-value for a procedural assignment.\n32: error: 'out' is not a valid l-value for a procedural assignment.\n6: : 'out' is declared here as a wire.\n"} {"task_id": "kmap3", "description": "Implement the circuit described by the Karnaugh map below. d is don't-care, which means you may choose to output whatever value is convenient.\n\n// ab\n// cd 01 00 10 11\n// 00 | d | 0 | 1 | 1 |\n// 01 | 0 | 0 | d | d |\n// 11 | 0 | 1 | 1 | 1 |\n// 10 | 0 | 1 | 1 | 1 |", "module_header": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput reg out\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput reg out\n);\n\n\talways @(posedge clk) begin\n\t\tout <= (a ^ b) ^ (c ^ d);\n\tend\n\nendmodule", "error": "9: error: Failed to evaluate event expression 'posedge clk'.\n9: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "kmap4", "description": "Implement the circuit described by the Karnaugh map below.\n\n// ab\n// cd 00 01 11 10\n// 00 | 0 | 1 | 0 | 1 |\n// 01 | 1 | 0 | 1 | 0 |\n// 11 | 0 | 1 | 0 | 1 |\n// 10 | 1 | 0 | 1 | 0 |", "module_header": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput reg out\n);\n", "original_code": "module top_module (\n\tinput a, \n\tinput b,\n\tinput c,\n\tinput d,\n\toutput reg out\n);\n parameter [0:1] a = 0;\n parameter [0:1] b = 0;\n parameter [0:1] c = 0;\n parameter [0:1] d = 0;\n\nalways @(*) begin\n case ({a,b,c,d})\n 4'b0000: out = 1'b0;\n 4'b0001: out = 1'b1;\n 4'b0011: out = 1'b0;\n 4'b0010: out = 1'b1;\n 4'b0100: out = 1'b0;\n 4'b0101: out = 1'b1;\n 4'b0111: out = 1'b0;\n 4'b0110: out = 1'b1;\n 4'b1000: out = 1'b0;\n 4'b1001: out = 1'b1;\n 4'b1011: out = 1'b0;\n 4'b1010: out = 1'b1;\n 4'b1100: out = 1'b0;\n 4'b1101: out = 1'b1;\n 4'b1111: out = 1'b0;\n 4'b1110: out = 1'b1;\n default: out = 1'b0;\n endcase\nend\n\nendmodule", "error": "11: error: 'd' has already been declared in this scope.\n4: : It was declared here as a net.\n2: : It was declared here as a net.\n8: error: 'a' has already been declared in this scope.\n5: : It was declared here as a net.\n9: error: 'b' has already been declared in this scope.\n10: error: 'c' has already been declared in this scope.\n3: : It was declared here as a net.\n"} {"task_id": "lemmings1", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. Implement a Moore state machine with two states, two inputs, and one output (internal to the module) that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\toutput walk_left,\n\toutput walk_right\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\toutput walk_left,\n\toutput walk_right\n);\n parameter IDLE = 2'b00;\n parameter LEFT = 2'b01;\n parameter RIGHT = 2'b10;\n parameter BOTH = 2'b11;\n\n reg [1:0] state, next_state;\n reg walk_left, walk_right;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= IDLE;\n walk_left <= 0;\n walk_right <= 0;\n end else begin\n state <= next_state;\n walk_left <= (state == LEFT) ? 1 : 0;\n walk_right <= (state == RIGHT) ? 1 : 0;\n end\n end\n\n always @* begin\n case (state)\n IDLE: begin\n if (bump_left) begin\n next_state = LEFT;\n end else if (bump_right) begin\n next_state = RIGHT;\n end else begin\n next_state = IDLE;\n end\n end\n LEFT: begin\n if (bump_right) begin\n next_state = RIGHT;\n end else if (bump_left && bump_right) begin\n next_state = BOTH;\n end else begin\n next_state = LEFT;\n end\n end\n RIGHT: begin\n if (bump_left) begin\n next_state = LEFT;\n end else if (bump_left && bump_right) begin\n next_state = BOTH;\n end else begin\n next_state = RIGHT;\n end\n end\n BOTH: begin\n if (bump_left && bump_right) begin\n next_state = BOTH;\n end else if (bump_left) begin\n next_state = LEFT;\n end else if (bump_right) begin\n next_state = RIGHT;\n end\n end\n endcase\n end\n\nendmodule", "error": "7: : It was declared here as a net.\n15: error: 'walk_right' has already been declared in this scope.\n15: error: 'walk_left' has already been declared in this scope.\n6: : It was declared here as a net.\n"} {"task_id": "lemmings1", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. Implement a Moore state machine with two states, two inputs, and one output (internal to the module) that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\toutput walk_left,\n\toutput walk_right\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\toutput walk_left,\n\toutput walk_right\n);\n parameter IDLE = 2'b00;\n parameter WALK_LEFT = 2'b01;\n parameter WALK_RIGHT = 2'b10;\n parameter IDLE_RIGHT = 2'b11;\n\n reg [1:0] state, next_state;\n reg walk_left, walk_right;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= IDLE;\n walk_left <= 1'b0;\n walk_right <= 1'b0;\n end else begin\n state <= next_state;\n walk_left <= (state == WALK_LEFT);\n walk_right <= (state == WALK_RIGHT);\n end\n end\n\n always @(*) begin\n case (state)\n IDLE: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = IDLE;\n end\n end\n WALK_LEFT: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (bump_right) begin\n next_state = IDLE_RIGHT;\n end else begin\n next_state = WALK_LEFT;\n end\n end\n WALK_RIGHT: begin\n if (bump_left) begin\n next_state = IDLE_RIGHT;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = WALK_RIGHT;\n end\n end\n IDLE_RIGHT: begin\n if (bump_left) begin\n next_state = WALK_LEFT;\n end else if (bump_right) begin\n next_state = WALK_RIGHT;\n end else begin\n next_state = IDLE_RIGHT;\n end\n end\n endcase\n end\n\nendmodule", "error": "7: : It was declared here as a net.\n15: error: 'walk_right' has already been declared in this scope.\n15: error: 'walk_left' has already been declared in this scope.\n6: : It was declared here as a net.\n"} {"task_id": "lemmings2", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"aaah!\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah\n);\n // Implementing the Lemming Moore state machine using Verilog\n wire [1:0] state, next_state;\n\n // State definitions\n parameter WALK_LEFT = 2'b00, WALK_RIGHT = 2'b01, FALL_LEFT = 2'b10, FALL_RIGHT = 2'b11;\n\n // Default values\n assign walk_left = 1'b0;\n assign walk_right = 1'b0;\n assign aaah = 1'b0;\n\n // State transition logic\n always @ (posedge clk or posedge areset) begin\n if (areset) begin\n state <= WALK_LEFT; // Reset to walk left\n end else begin\n state <= next_state;\n end\n end\n\n // Next state logic\n always @ (state, bump_left, bump_right, ground) begin\n case (state)\n WALK_LEFT: begin\n if (bump_right) begin\n next_state = WALK_RIGHT; // Walk right if bumped\n end else if (ground == 0) begin\n next_state = FALL_RIGHT; // Fall if ground is not available\n end else begin\n next_state = WALK_LEFT; // Continue walking to the left\n end\n end\n WALK_RIGHT: begin\n if (bump_left) begin\n next_state = WALK_LEFT; // Walk left if bumped\n end else if (ground == 0) begin\n next_state = FALL_LEFT; // Fall if ground is not available\n end else begin\n next_state = WALK_RIGHT; // Continue walking to the right\n end\n end\n FALL_LEFT: begin\n if (bump_right) begin\n next_state = WALK_RIGHT; // Continue walking right when falling\n end else if (ground) begin // Resume walking left when ground reappears\n next_state = WALK_LEFT;\n end else begin\n next_state = FALL_LEFT; // Continue falling\n end\n end\n FALL_RIGHT: begin\n if (bump_left) begin\n next_state = WALK_LEFT; // Continue walking left when falling\n end else if (ground) begin // Resume walking right when ground reappears\n next_state = WALK_RIGHT;\n end else begin\n next_state = FALL_RIGHT; // Continue falling\n end\n end\n default: begin\n next_state = WALK_LEFT; // Default to walking left\n end\n endcase\n end\n\n // Output logic\n always @ (state) begin\n case (state)\n WALK_LEFT, FALL_LEFT: begin\n walk_left = 1'b1;\n walk_right = 1'b0;\n aaah = ground;\n end\n WALK_RIGHT, FALL_RIGHT: begin\n walk_left = 1'b0;\n walk_right = 1'b1;\n aaah = ground;\n end\n default: begin\n walk_left = 1'b0;\n walk_right = 1'b0;\n aaah = 1'b0;\n end\n endcase\n end\n\nendmodule", "error": "71: error: 'next_state' is not a valid l-value for a procedural assignment.\n65: error: 'next_state' is not a valid l-value for a procedural assignment.\n36: error: 'next_state' is not a valid l-value for a procedural assignment.\n86: error: 'walk_right' is not a valid l-value for a procedural assignment.\n9: : 'aaah' is declared here as a wire.\n12: : 'next_state' is declared here as a wire.\n27: error: 'state' is not a valid l-value for a procedural assignment.\n82: error: 'aaah' is not a valid l-value for a procedural assignment.\n87: error: 'aaah' is not a valid l-value for a procedural assignment.\n38: error: 'next_state' is not a valid l-value for a procedural assignment.\n80: error: 'walk_left' is not a valid l-value for a procedural assignment.\n8: : 'walk_right' is declared here as a wire.\n56: error: 'next_state' is not a valid l-value for a procedural assignment.\n90: error: 'walk_left' is not a valid l-value for a procedural assignment.\n85: error: 'walk_left' is not a valid l-value for a procedural assignment.\n81: error: 'walk_right' is not a valid l-value for a procedural assignment.\n47: error: 'next_state' is not a valid l-value for a procedural assignment.\n12: : 'state' is declared here as a wire.\n91: error: 'walk_right' is not a valid l-value for a procedural assignment.\n49: error: 'next_state' is not a valid l-value for a procedural assignment.\n67: error: 'next_state' is not a valid l-value for a procedural assignment.\n63: error: 'next_state' is not a valid l-value for a procedural assignment.\n92: error: 'aaah' is not a valid l-value for a procedural assignment.\n25: error: 'state' is not a valid l-value for a procedural assignment.\n58: error: 'next_state' is not a valid l-value for a procedural assignment.\n7: : 'walk_left' is declared here as a wire.\n40: error: 'next_state' is not a valid l-value for a procedural assignment.\n45: error: 'next_state' is not a valid l-value for a procedural assignment.\n54: error: 'next_state' is not a valid l-value for a procedural assignment.\n"} {"task_id": "lemmings2", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"aaah!\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah\n);\n parameter IDLE = 2'b00, WALK_LEFT = 2'b01, WALK_RIGHT = 2'b10;\n reg [1:0] state, next_state;\n reg walk_left_reg, walk_right_reg;\n reg aaah_reg;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= IDLE;\n walk_left_reg <= 1'b0;\n walk_right_reg <= 1'b0;\n aaah_reg <= 1'b0;\n end else begin\n state <= next_state;\n walk_left_reg <= walk_left;\n walk_right_reg <= walk_right;\n aaah_reg <= aaah;\n end\n end\n\n always @(*) begin\n next_state = state;\n walk_left = walk_left_reg;\n walk_right = walk_right_reg;\n aaah = aaah_reg;\n case (state)\n IDLE: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n walk_left = 1'b0;\n walk_right = 1'b1;\n aaah = 1'b0;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n walk_left = 1'b1;\n walk_right = 1'b0;\n aaah = 1'b0;\n end else if (ground == 1'b0) begin\n next_state = IDLE;\n walk_left = 1'b0;\n walk_right = 1'b0;\n aaah = 1'b1;\n end else begin\n next_state = IDLE;\n walk_left = 1'b0;\n walk_right = 1'b0;\n aaah = 1'b0;\n end\n end\n WALK_LEFT: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n walk_left = 1'b0;\n walk_right = 1'b1;\n aaah = 1'b0;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n walk_left = 1'b1;\n walk_right = 1'b0;\n aaah = 1'b0;\n end else if (ground == 1'b0) begin\n next_state = IDLE;\n walk_left = 1'b0;\n walk_right = 1'b0;\n aaah = 1'b1;\n end else begin\n next_state = WALK_LEFT;\n walk_left = 1'b1;\n walk_right = 1'b0;\n aaah = 1'b0;\n end\n end\n WALK_RIGHT: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n walk_left = 1'b0;\n walk_right = 1'b1;\n aaah = 1'b0;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n walk_left = 1'b1;\n walk_right = 1'b0;\n aaah = 1'b0;\n end else if (ground == 1'b0) begin\n next_state = IDLE;\n walk_left = 1'b0;\n walk_right = 1'b0;\n aaah = 1'b1;\n end else begin\n next_state = WALK_RIGHT;\n walk_left = 1'b0;\n walk_right = 1'b1;\n aaah = 1'b0;\n end\n end\n endcase\n end\n\nendmodule", "error": "44: error: 'walk_left' is not a valid l-value for a procedural assignment.\n51: error: 'aaah' is not a valid l-value for a procedural assignment.\n86: error: 'walk_right' is not a valid l-value for a procedural assignment.\n9: : 'aaah' is declared here as a wire.\n55: error: 'walk_right' is not a valid l-value for a procedural assignment.\n77: error: 'walk_left' is not a valid l-value for a procedural assignment.\n102: error: 'aaah' is not a valid l-value for a procedural assignment.\n49: error: 'walk_left' is not a valid l-value for a procedural assignment.\n87: error: 'aaah' is not a valid l-value for a procedural assignment.\n64: error: 'aaah' is not a valid l-value for a procedural assignment.\n40: error: 'walk_right' is not a valid l-value for a procedural assignment.\n8: : 'walk_right' is declared here as a wire.\n41: error: 'aaah' is not a valid l-value for a procedural assignment.\n74: error: 'aaah' is not a valid l-value for a procedural assignment.\n62: error: 'walk_left' is not a valid l-value for a procedural assignment.\n100: error: 'walk_left' is not a valid l-value for a procedural assignment.\n95: error: 'walk_left' is not a valid l-value for a procedural assignment.\n45: error: 'walk_right' is not a valid l-value for a procedural assignment.\n46: error: 'aaah' is not a valid l-value for a procedural assignment.\n63: error: 'walk_right' is not a valid l-value for a procedural assignment.\n85: error: 'walk_left' is not a valid l-value for a procedural assignment.\n90: error: 'walk_left' is not a valid l-value for a procedural assignment.\n79: error: 'aaah' is not a valid l-value for a procedural assignment.\n56: error: 'aaah' is not a valid l-value for a procedural assignment.\n50: error: 'walk_right' is not a valid l-value for a procedural assignment.\n91: error: 'walk_right' is not a valid l-value for a procedural assignment.\n78: error: 'walk_right' is not a valid l-value for a procedural assignment.\n68: error: 'walk_right' is not a valid l-value for a procedural assignment.\n92: error: 'aaah' is not a valid l-value for a procedural assignment.\n54: error: 'walk_left' is not a valid l-value for a procedural assignment.\n67: error: 'walk_left' is not a valid l-value for a procedural assignment.\n73: error: 'walk_right' is not a valid l-value for a procedural assignment.\n72: error: 'walk_left' is not a valid l-value for a procedural assignment.\n96: error: 'walk_right' is not a valid l-value for a procedural assignment.\n7: : 'walk_left' is declared here as a wire.\n97: error: 'aaah' is not a valid l-value for a procedural assignment.\n101: error: 'walk_right' is not a valid l-value for a procedural assignment.\n34: error: 'aaah' is not a valid l-value for a procedural assignment.\n32: error: 'walk_left' is not a valid l-value for a procedural assignment.\n69: error: 'aaah' is not a valid l-value for a procedural assignment.\n39: error: 'walk_left' is not a valid l-value for a procedural assignment.\n33: error: 'walk_right' is not a valid l-value for a procedural assignment.\n"} {"task_id": "lemmings3", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"aaah!\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// In addition to walking and falling, Lemmings can sometimes be told to do useful things, like dig (it starts digging when dig=1). A Lemming can dig if it is currently walking on ground (ground=1 and not falling), and will continue digging until it reaches the other side (ground=0). At that point, since there is no ground, it will fall (aaah!), then continue walking in its original direction once it hits ground again. As with falling, being bumped while digging has no effect, and being told to dig when falling or when there is no ground is ignored. (In other words, a walking Lemming can fall, dig, or switch directions. If more than one of these conditions are satisfied, fall has higher precedence than dig, which has higher precedence than switching directions.)\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n parameter IDLE = 2'b00;\n parameter WALK_LEFT = 2'b01;\n parameter WALK_RIGHT = 2'b10;\n parameter FALL = 2'b11;\n\n reg [1:0] state, next_state;\n reg walk_left, walk_right, aaah, digging;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= IDLE;\n walk_left <= 0;\n walk_right <= 0;\n aaah <= 0;\n digging <= 0;\n end else begin\n state <= next_state;\n walk_left <= (state == WALK_LEFT);\n walk_right <= (state == WALK_RIGHT);\n aaah <= (state == FALL);\n digging <= (state == WALK_LEFT || state == WALK_RIGHT);\n end\n end\n\n always @(*) begin\n case (state)\n IDLE: begin\n if (dig) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = IDLE;\n end\n end\n WALK_LEFT: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n end else if (dig) begin\n next_state = WALK_LEFT;\n end else if (ground == 0) begin\n next_state = FALL;\n end else begin\n next_state = WALK_LEFT;\n end\n end\n WALK_RIGHT: begin\n if (bump_right) begin\n next_state = WALK_LEFT;\n end else if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (dig) begin\n next_state = WALK_RIGHT;\n end else if (ground == 0) begin\n next_state = FALL;\n end else begin\n next_state = WALK_RIGHT;\n end\n end\n FALL: begin\n if (ground == 1) begin\n next_state = WALK_LEFT;\n end else if (dig) begin\n next_state = WALK_RIGHT;\n end else begin\n next_state = FALL;\n end\n end\n default: begin\n next_state = IDLE;\n end\n endcase\n end\n\nendmodule", "error": "19: error: 'walk_left' has already been declared in this scope.\n11: : It was declared here as a net.\n8: : It was declared here as a net.\n9: : It was declared here as a net.\n19: error: 'aaah' has already been declared in this scope.\n19: error: 'walk_right' has already been declared in this scope.\n19: error: 'digging' has already been declared in this scope.\n10: : It was declared here as a net.\n"} {"task_id": "lemmings3", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"aaah!\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// In addition to walking and falling, Lemmings can sometimes be told to do useful things, like dig (it starts digging when dig=1). A Lemming can dig if it is currently walking on ground (ground=1 and not falling), and will continue digging until it reaches the other side (ground=0). At that point, since there is no ground, it will fall (aaah!), then continue walking in its original direction once it hits ground again. As with falling, being bumped while digging has no effect, and being told to dig when falling or when there is no ground is ignored. (In other words, a walking Lemming can fall, dig, or switch directions. If more than one of these conditions are satisfied, fall has higher precedence than dig, which has higher precedence than switching directions.)\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n parameter IDLE = 2'b00;\n parameter WALK_LEFT = 2'b01;\n parameter WALK_RIGHT = 2'b10;\n parameter FALL = 2'b11;\n\n reg [1:0] state, next_state;\n reg walk_left, walk_right, aaah, digging;\n\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= IDLE;\n walk_left <= 0;\n walk_right <= 0;\n aaah <= 0;\n digging <= 0;\n end else begin\n state <= next_state;\n walk_left <= (state == WALK_LEFT);\n walk_right <= (state == WALK_RIGHT);\n aaah <= (state == FALL);\n digging <= (state == WALK_LEFT || state == WALK_RIGHT);\n end\n end\n\n always @(*) begin\n case (state)\n IDLE: begin\n if (dig) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = WALK_RIGHT;\n end\n end\n WALK_LEFT: begin\n if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (bump_right) begin\n next_state = WALK_LEFT;\n end else if (ground == 0) begin\n next_state = FALL;\n end else if (dig) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = WALK_LEFT;\n end\n end\n WALK_RIGHT: begin\n if (bump_right) begin\n next_state = WALK_LEFT;\n end else if (bump_left) begin\n next_state = WALK_RIGHT;\n end else if (ground == 0) begin\n next_state = FALL;\n end else if (dig) begin\n next_state = WALK_RIGHT;\n end else begin\n next_state = WALK_RIGHT;\n end\n end\n FALL: begin\n if (ground) begin\n next_state = WALK_LEFT;\n end else begin\n next_state = FALL;\n end\n end\n endcase\n end\n\nendmodule", "error": "19: error: 'walk_left' has already been declared in this scope.\n11: : It was declared here as a net.\n8: : It was declared here as a net.\n9: : It was declared here as a net.\n19: error: 'aaah' has already been declared in this scope.\n19: error: 'walk_right' has already been declared in this scope.\n19: error: 'digging' has already been declared in this scope.\n10: : It was declared here as a net.\n"} {"task_id": "lemmings4", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"\"aaah!\"\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// In addition to walking and falling, Lemmings can sometimes be told to do useful things, like dig (it starts digging when dig=1). A Lemming can dig if it is currently walking on ground (ground=1 and not falling), and will continue digging until it reaches the other side (ground=0). At that point, since there is no ground, it will fall (aaah!), then continue walking in its original direction once it hits ground again. As with falling, being bumped while digging has no effect, and being told to dig when falling or when there is no ground is ignored. (In other words, a walking Lemming can fall, dig, or switch directions. If more than one of these conditions are satisfied, fall has higher precedence than dig, which has higher precedence than switching directions.)\n// Although Lemmings can walk, fall, and dig, Lemmings aren't invulnerable. If a Lemming falls for too long then hits the ground, it can splatter. In particular, if a Lemming falls for more than 20 clock cycles then hits the ground, it will splatter and cease walking, falling, or digging (all 4 outputs become 0), forever (Or until the FSM gets reset). There is no upper limit on how far a Lemming can fall before hitting the ground. Lemmings only splatter when hitting the ground; they do not splatter in mid-air.\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n // State definitions\n parameter WALK_LEFT = 2'b00;\n parameter WALK_RIGHT = 2'b01;\n parameter FALL = 2'b10;\n parameter SPLAT = 2'b11;\n\n // State variables\n reg [1:0] state;\n reg [2:0] fall_counter;\n reg [1:0] dig_counter;\n reg splat;\n\n // Output variables\n reg walk_left_out;\n reg walk_right_out;\n reg aaah_out;\n reg digging_out;\n\n // Reset logic\n always @(posedge clk or posedge areset) begin\n if (areset) begin\n state <= WALK_LEFT;\n fall_counter <= 0;\n dig_counter <= 0;\n splat <= 0;\n end else begin\n // State transitions\n case (state)\n WALK_LEFT: begin\n if (bump_left || bump_right) begin\n state <= WALK_RIGHT;\n end else if (!ground) begin\n state <= FALL;\n end else if (dig) begin\n state <= DIGGING;\n end\n end\n WALK_RIGHT: begin\n if (bump_left || bump_right) begin\n state <= WALK_LEFT;\n end else if (!ground) begin\n state <= FALL;\n end else if (dig) begin\n state <= DIGGING;\n end\n end\n FALL: begin\n if (ground) begin\n state <= WALK_LEFT;\n end else if (bump_left || bump_right) begin\n state <= SPLAT;\n end else if (fall_counter == 20) begin\n state <= SPLAT;\n end else begin\n fall_counter <= fall_counter + 1;\n end\n end\n DIGGING: begin\n if (!ground) begin\n state <= FALL;\n end else if (dig_counter == 2) begin\n state <= WALK_LEFT;\n end else if (dig_counter == 1) begin\n state <= WALK_RIGHT;\n end else begin\n dig_counter <= dig_counter + 1;\n end\n end\n SPLAT: begin\n if (!bump_left && !bump_right && !ground) begin\n state <= SPLAT;\n end else begin\n splat <= 1;\n state <= SPLAT;\n end\n end\n endcase\n end\n end\n\n // Output logic\n always @(state) begin\n case (state)\n WALK_LEFT: begin\n walk_left_out = 1;\n walk_right_out = 0;\n aaah_out = 0;\n digging_out = 0;\n end\n WALK_RIGHT: begin\n walk_left_out = 0;\n walk_right_out = 1;\n aaah_out = 0;\n digging_out = 0;\n end\n FALL: begin\n walk_left_out = 0;\n walk_right_out = 0;\n aaah_out = 1;\n digging_out = 0;\n end\n DIGGING: begin\n walk_left_out = 0;\n walk_right_out = 0;\n aaah_out = 0;\n digging_out = 1;\n end\n SPLAT: begin\n walk_left_out = 0;\n walk_right_out = 0;\n aaah_out = 0;\n digging_out = 0;\n end\n endcase\n end\n\n // Output assignments\n assign walk_left = walk_left_out;\n assign walk_right = walk_right_out;\n assign aaah = aaah_out;\n assign digging = digging_out;\n\nendmodule", "error": "114: error: Unable to bind wire/reg/memory `DIGGING' in `top_module'\n47: error: Unable to bind wire/reg/memory `DIGGING' in `top_module'\n70: error: Unable to bind wire/reg/memory `DIGGING' in `top_module'\n56: error: Unable to bind wire/reg/memory `DIGGING' in `top_module'\n"} {"task_id": "lemmings4", "description": "The game Lemmings involves critters with fairly simple brains. So simple that we are going to model it using a finite state machine. In the Lemmings' 2D world, Lemmings can be in one of two states: walking left (walk_left is 1) or walking right (walk_right is 1). It will switch directions if it hits an obstacle. In particular, if a Lemming is bumped on the left (by receiving a 1 on bump_left), it will walk right. If it's bumped on the right (by receiving a 1 on bump_right), it will walk left. If it's bumped on both sides at the same time, it will still switch directions. \n// In addition to walking left and right and changing direction when bumped, when ground=0, the Lemming will fall and say \"\"aaah!\"\". When the ground reappears (ground=1), the Lemming will resume walking in the same direction as before the fall. Being bumped while falling does not affect the walking direction, and being bumped in the same cycle as ground disappears (but not yet falling), or when the ground reappears while still falling, also does not affect the walking direction.\n// In addition to walking and falling, Lemmings can sometimes be told to do useful things, like dig (it starts digging when dig=1). A Lemming can dig if it is currently walking on ground (ground=1 and not falling), and will continue digging until it reaches the other side (ground=0). At that point, since there is no ground, it will fall (aaah!), then continue walking in its original direction once it hits ground again. As with falling, being bumped while digging has no effect, and being told to dig when falling or when there is no ground is ignored. (In other words, a walking Lemming can fall, dig, or switch directions. If more than one of these conditions are satisfied, fall has higher precedence than dig, which has higher precedence than switching directions.)\n// Although Lemmings can walk, fall, and dig, Lemmings aren't invulnerable. If a Lemming falls for too long then hits the ground, it can splatter. In particular, if a Lemming falls for more than 20 clock cycles then hits the ground, it will splatter and cease walking, falling, or digging (all 4 outputs become 0), forever (Or until the FSM gets reset). There is no upper limit on how far a Lemming can fall before hitting the ground. Lemmings only splatter when hitting the ground; they do not splatter in mid-air.\n// Implement a Moore state machine that models this behaviour. areset is positive edge triggered asynchronous reseting the Lemming machine to walk left.", "module_header": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput areset,\n\tinput bump_left,\n\tinput bump_right,\n\tinput ground,\n\tinput dig,\n\toutput walk_left,\n\toutput walk_right,\n\toutput aaah,\n\toutput digging\n);\n parameter IDLE = 2'b00;\n parameter WALKING_LEFT = 2'b01;\n parameter FALLING = 2'b10;\n parameter DIGGING = 2'b11;\n\n reg [1:0] state, next_state;\n reg walk_left, walk_right, aaah, digging;\n\n always @(posedge clk) begin\n if (areset) begin\n state <= IDLE;\n walk_left <= 0;\n walk_right <= 0;\n aaah <= 0;\n digging <= 0;\n end else begin\n state <= next_state;\n end\n end\n\n always @* begin\n next_state = state;\n walk_left = 0;\n walk_right = 0;\n aaah = 0;\n digging = 0;\n\n case (state)\n IDLE: begin\n if (bump_left && !bump_right) begin\n next_state = WALKING_LEFT;\n walk_left = 1;\n end else if (bump_right && !bump_left) begin\n next_state = WALKING_LEFT;\n walk_right = 1;\n end else if (bump_left && bump_right) begin\n next_state = WALKING_LEFT;\n walk_left = 1;\n walk_right = 1;\n end else if (dig) begin\n next_state = DIGGING;\n digging = 1;\n end else if (bump_left || bump_right) begin\n next_state = FALLING;\n aaah = 1;\n end\n end\n\n WALKING_LEFT: begin\n if (bump_left && !bump_right) begin\n walk_left = 1;\n end else if (bump_right && !bump_left) begin\n walk_right = 1;\n next_state = WALKING_LEFT;\n end else if (bump_left && bump_right) begin\n walk_left = 1;\n walk_right = 1;\n next_state = WALKING_LEFT;\n end else if (dig) begin\n next_state = DIGGING;\n digging = 1;\n end else if (bump_left || bump_right) begin\n next_state = FALLING;\n aaah = 1;\n end\n end\n\n FALLING: begin\n if (ground) begin\n next_state = IDLE;\n aaah = 0;\n end\n end\n\n DIGGING: begin\n if (!dig) begin\n next_state = IDLE;\n digging = 0;\n end else if (ground) begin\n next_state = DIGGING;\n digging = 1;\n end else if (bump_left || bump_right) begin\n next_state = FALLING;\n aaah = 1;\n end\n end\n endcase\n end\nendmodule", "error": "19: error: 'walk_left' has already been declared in this scope.\n11: : It was declared here as a net.\n8: : It was declared here as a net.\n9: : It was declared here as a net.\n19: error: 'aaah' has already been declared in this scope.\n19: error: 'walk_right' has already been declared in this scope.\n19: error: 'digging' has already been declared in this scope.\n10: : It was declared here as a net.\n"} {"task_id": "lfsr32", "description": "A linear feedback shift register is a shift register usually with a few XOR gates to produce the next state of the shift register. A Galois LFSR is one particular arrangement where bit positions with a \"tap\" are XORed with the output bit to produce each bit's next value, while bit positions without a tap shift. Build a 32-bit Galois LFSR with taps at bit positions 32, 22, 2, and 1. Reset should be active high synchronous, and should reset the output q to 32'h1.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [31:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [31:0] q);\n parameter [31:0] TAP_POS = 32'h1 << 32 | 32'h1 << 22 | 32'h1 << 2 | 32'h1;\n\n always @(posedge clk) begin\n if (reset) begin\n q <= 32'h1;\n end\n else begin\n q <= (q[TAP_POS] ^ q[TAP_POS - 1] ^ q[TAP_POS - 2] ^ q[TAP_POS - 3]) << 1;\n end\n end\n endmodule", "error": "12: warning: Constant bit select [4194308] is after vector q[31:0].\n12: warning: Constant bit select [4194306] is after vector q[31:0].\n12: warning: Constant bit select [4194307] is after vector q[31:0].\n12: : Replacing select with a constant 1'bx.\n12: warning: Constant bit select [4194309] is after vector q[31:0].\n"} {"task_id": "lfsr32", "description": "A linear feedback shift register is a shift register usually with a few XOR gates to produce the next state of the shift register. A Galois LFSR is one particular arrangement where bit positions with a \"tap\" are XORed with the output bit to produce each bit's next value, while bit positions without a tap shift. Build a 32-bit Galois LFSR with taps at bit positions 32, 22, 2, and 1. Reset should be active high synchronous, and should reset the output q to 32'h1.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [31:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [31:0] q);\n\n reg [31:0] lfsr;\n reg [4:0] tap;\n integer i;\n\n always @(posedge clk) begin\n if (reset) begin\n lfsr <= 32'h1;\n end else begin\n tap <= {lfsr[32], lfsr[22], lfsr[2], lfsr[1]};\n lfsr <= {lfsr[31:1], tap[0] ^ tap[1] ^ tap[2] ^ tap[3]};\n end\n end\n\n assign q = lfsr;\n\nendmodule", "error": "14: : Replacing select with a constant 1'bx.\n14: warning: Constant bit select [32] is after vector lfsr[31:0].\n"} {"task_id": "lfsr5", "description": "A linear feedback shift register is a shift register usually with a few XOR gates to produce the next state of the shift register. A Galois LFSR is one particular arrangement where bit positions with a \"tap\" are XORed with the output bit to produce its next value, while bit positions without a tap shift. If the taps positions are carefully chosen, the LFSR can be made to be \"maximum-length\". A maximum-length LFSR of n bits cycles through 2**n-1 states before repeating (the all-zero state is never reached). Build a 5-bit maximal-length Galois LFSR with taps at bit positions 5 and 3. The active-high synchronous reset should reset the LFSR output to 1.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [4:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [4:0] q);\n reg r1;\n reg r2;\n\n initial begin\n r1 = 1;\n r2 = r1 ^ (q[5] ^ q[3]);\n end\n\n always @(posedge clk) begin\n if (reset) begin\n q <= 5'b00001;\n end else begin\n q <= r2;\n r1 <= r2;\n r2 <= r1 ^ (q[5] ^ q[3]);\n end\n end\n endmodule", "error": "19: : Replacing select with a constant 1'bx.\n10: : Replacing select with a constant 1'bx.\n19: warning: Constant bit select [5] is after vector q[4:0].\n10: warning: Constant bit select [5] is after vector q[4:0].\n"} {"task_id": "lfsr5", "description": "A linear feedback shift register is a shift register usually with a few XOR gates to produce the next state of the shift register. A Galois LFSR is one particular arrangement where bit positions with a \"tap\" are XORed with the output bit to produce its next value, while bit positions without a tap shift. If the taps positions are carefully chosen, the LFSR can be made to be \"maximum-length\". A maximum-length LFSR of n bits cycles through 2**n-1 states before repeating (the all-zero state is never reached). Build a 5-bit maximal-length Galois LFSR with taps at bit positions 5 and 3. The active-high synchronous reset should reset the LFSR output to 1.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [4:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [4:0] q);\n wire t1, t2, t3, t4, t5;\n wire fb1, fb2, fb3, fb4, fb5;\n reg [4:0] lfsr;\n initial begin \n lfsr = 5'b10000;\n end \n assign fb1 = (lfsr[0] ^ lfsr[1]);\n assign fb2 = (lfsr[0] ^ lfsr[2]);\n assign fb3 = (lfsr[0] ^ lfsr[4]);\n assign fb4 = (lfsr[1] ^ lfsr[2]);\n assign fb5 = (lfsr[2] ^ lfsr[4]);\n assign t1 = lfsr[5];\n assign t2 = fb1;\n assign t3 = fb2;\n assign t4 = fb3;\n assign t5 = fb4;\n always @(posedge clk) begin \n if (reset) begin\n lfsr <= 5'b10000;\n end else begin\n lfsr[4:0] <= {fb5,t1,t2,t3,t4};\n end\n end\n assign q = lfsr;\nendmodule", "error": "16: : Replacing select with a constant 1'bx.\n16: warning: Constant bit select [5] is after vector lfsr[4:0].\n"} {"task_id": "m2014_q3", "description": "Consider the function f shown in the Karnaugh map below. d is don't-care, which means you may choose to output whatever value is convenient. Implement this function. \n// x[1]x[2]\n// x[3]x[4] 00 01 11 10\n// 00 | d | 0 | d | d |\n// 01 | 0 | d | 1 | 0 |\n// 11 | 1 | 1 | d | d |\n// 10 | 1 | 1 | 0 | d |", "module_header": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n", "original_code": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n always @(*) begin\n case ({x4,x3,x2,x1})\n 4'b0000, 4'b0001, 4'b0011, 4'b0010: f = 1'b0;\n 4'b0100, 4'b0101, 4'b0111, 4'b0110: f = 1'b1;\n default: f = 1'b0;\n endcase\n end\n\nendmodule", "error": "6: error: Unable to bind wire/reg/memory `x1' in `top_module'\n6: error: Unable to bind wire/reg/memory `x2' in `top_module'\n6: error: Unable to bind wire/reg/memory `x3' in `top_module'\n6: error: Unable to bind wire/reg/memory `x4' in `top_module'\n6: error: Unable to elaborate this case expression.\n6: error: Concatenation/replication may not have zero width in this context.\n"} {"task_id": "m2014_q3", "description": "Consider the function f shown in the Karnaugh map below. d is don't-care, which means you may choose to output whatever value is convenient. Implement this function. \n// x[1]x[2]\n// x[3]x[4] 00 01 11 10\n// 00 | d | 0 | d | d |\n// 01 | 0 | d | 1 | 0 |\n// 11 | 1 | 1 | d | d |\n// 10 | 1 | 1 | 0 | d |", "module_header": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\n", "original_code": "module top_module (\n\tinput [4:1] x,\n\toutput logic f\n);\nalways_comb begin\n\tcasex({x[4],x[3],x[2],x[1]})\n\t\t4'b0000, 4'b0010, 4'b0110, 4'b0100, 4'b1100, 4'b1000, 4'b1010, 4'b1110: f = 0;\n\t\t4'b0011, 4'b0111, 4'b1111, 4'b1011: f = 1;\n\t\tdefault: f = 1'bx;\n\tendcase\nend\n\nendmodule", "error": "5: sorry: constant selects in always_* processes are not currently supported (all bits will be included).\n"} {"task_id": "m2014_q4b", "description": "Implement a D flip flop, positive edge triggered, with an asynchronous reset \"ar\".", "module_header": "module top_module (\n\tinput clk,\n\tinput d,\n\tinput ar,\n\toutput logic q\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput d,\n\tinput ar,\n\toutput logic q\n);\n parameter WIDTH = 1;\n\n\tdffl_ar #(.WIDTH(WIDTH)) dut (.d(d), .clk(clk), .ar(ar), .q(q));\n\n\tendmodule", "error": "9: error: Unknown module type: dffl_ar\n"} {"task_id": "m2014_q4c", "description": "Implement a simple D flip flop with active high synchronous reset (reset output to 0).", "module_header": "module top_module (\n\tinput clk,\n\tinput d,\n\tinput r,\n\toutput logic q\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput d,\n\tinput r,\n\toutput logic q\n);\n assign q = (r) ? 1'b0 : q;\n\n\talways @(posedge clk)\n\t\tq <= d;\n\t\t\nendmodule", "error": "10: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n"} {"task_id": "m2014_q4d", "description": "Implement in Verilog the following circuit: A D flip-flop takes as input the output of a two-input XOR. The flip-flop is positive edge triggered by clk, but there is no reset. The XOR takes as input 'in' along with the output 'out' of the flip-flop.", "module_header": "module top_module (\n\tinput clk,\n\tinput in,\n\toutput logic out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput in,\n\toutput logic out\n);\n\tlogic xor_out;\n\tlogic flipflop_out;\n\n\txor_gate xor_gate_instance (\n\t\t.a(in),\n\t\t.b(flipflop_out),\n\t\t.out(xor_out)\n\t);\n\n\td_flip_flop d_flip_flop_instance (\n\t\t.clk(clk),\n\t\t.d(xor_out),\n\t\t.q(flipflop_out)\n\t);\n\n\tassign out = flipflop_out;\n\nendmodule", "error": "9: error: Unknown module type: xor_gate\n15: error: Unknown module type: d_flip_flop\n"} {"task_id": "m2014_q4f", "description": "Implement the following circuit in Verilog. Two inputs (in1 and in2) go to an AND gate, but the in2 input to the AND gate has a bubble. The output of the AND gate is connected to 'out'.", "module_header": "module top_module (\n\tinput in1,\n\tinput in2,\n\toutput logic out\n);\n", "original_code": "module top_module (\n\tinput in1,\n\tinput in2,\n\toutput logic out\n);\n // Module definition with input and output ports.\n\n\twire and_out;\n\n\tand and_gate (\n\t\t.a(in1),\n\t\t.b(in2),\n\t\t.z(and_out)\n\t);\n\n\tassign out = and_out;\n\nendmodule", "error": "10: error: Gates do not have port names.\n"} {"task_id": "m2014_q4f", "description": "Implement the following circuit in Verilog. Two inputs (in1 and in2) go to an AND gate, but the in2 input to the AND gate has a bubble. The output of the AND gate is connected to 'out'.", "module_header": "module top_module (\n\tinput in1,\n\tinput in2,\n\toutput logic out\n);\n", "original_code": "module top_module (\n\tinput in1,\n\tinput in2,\n\toutput logic out\n);\n logic and_out;\n\n and_gate and_inst (\n .in1(in1),\n .in2(in2),\n .out(and_out)\n );\n\n assign out = and_out;\n\nendmodule", "error": "8: error: Unknown module type: and_gate\n"} {"task_id": "m2014_q4g", "description": "Implement in Verilog the following circuit: A two-input XNOR (connected to 'in1' and 'in2) has an output connected to the input of a two-input XOR. The second input of the XOR is 'in3.' The output of the XOR is 'out'.", "module_header": "module top_module (\n\tinput in1,\n\tinput in2,\n\tinput in3,\n\toutput logic out\n);\n", "original_code": "module top_module (\n\tinput in1,\n\tinput in2,\n\tinput in3,\n\toutput logic out\n);\n // Name Output Other arguments\n xnor0 (xnor_out, in1, in2); // Instantiate xnor gate with output xnor_out and inputs in1, in2.\n xor0 (out, xnor_out, in3); // Instantiate xor gate with output out and inputs xnor_out, in3.\n\nendmodule", "error": "9: error: Unknown module type: xor0\n8: error: Unknown module type: xnor0\n8: warning: implicit definition of wire 'xnor_out'.\n"} {"task_id": "m2014_q4g", "description": "Implement in Verilog the following circuit: A two-input XNOR (connected to 'in1' and 'in2) has an output connected to the input of a two-input XOR. The second input of the XOR is 'in3.' The output of the XOR is 'out'.", "module_header": "module top_module (\n\tinput in1,\n\tinput in2,\n\tinput in3,\n\toutput logic out\n);\n", "original_code": "module top_module (\n\tinput in1,\n\tinput in2,\n\tinput in3,\n\toutput logic out\n);\n // Name Output Other arguments\n xnor2 xnor_inst (out, in1, in2);\n xor2 xor_inst (out, out, in3);\n\nendmodule", "error": "8: error: Unknown module type: xnor2\n9: error: Unknown module type: xor2\n"} {"task_id": "m2014_q4i", "description": "Build a circuit with no inputs and one output. That output should always drive 0 (or logic low).", "module_header": "module top_module(\n\toutput out);\n", "original_code": "module top_module(\n\toutput out);\n // Module supplies\n supply1 VPWR;\n supply0 VGND;\n supply1 VPB ;\n supply0 VNB ;\n\n // Instantiate the module\n always @(*) begin\n out <= 1'b0;\n end\n\nendmodule", "error": "11: error: 'out' is not a valid l-value for a procedural assignment.\n2: : 'out' is declared here as a wire.\n"} {"task_id": "m2014_q4i", "description": "Build a circuit with no inputs and one output. That output should always drive 0 (or logic low).", "module_header": "module top_module(\n\toutput out);\n", "original_code": "module top_module(\n\toutput out);\nreg out_reg;\n assign out = out_reg;\n always @(*) begin\n\tout_reg = 1'b0;\n end\n \nendmodule\n", "error": "5: warning: @* found no sensitivities so it will never trigger.\n"} {"task_id": "m2014_q4j", "description": "Implement a 4-bit adder with full adders. The output sum should include the overflow bit.", "module_header": "module top_module (\n\tinput [3:0] x,\n\tinput [3:0] y,\n\toutput [4:0] sum\n);\n", "original_code": "module top_module (\n\tinput [3:0] x,\n\tinput [3:0] y,\n\toutput [4:0] sum\n);\n // Define carry signals for each bit\n wire c1, c2, c3;\n\n // Define full adder modules\n full_adder fa0(.a(x[0]), .b(y[0]), .c(1'b0), .sum(sum[0]), .carry(c1));\n full_adder fa1(.a(x[1]), .b(y[1]), .c(c1), .sum(sum[1]), .carry(c2));\n full_adder fa2(.a(x[2]), .b(y[2]), .c(c2), .sum(sum[2]), .carry(c3));\n full_adder fa3(.a(x[3]), .b(y[3]), .c(c3), .sum(sum[3]), .carry(sum[4]));\n\nendmodule", "error": "13: error: Unknown module type: full_adder\n12: error: Unknown module type: full_adder\n11: error: Unknown module type: full_adder\n10: error: Unknown module type: full_adder\n"} {"task_id": "m2014_q4j", "description": "Implement a 4-bit adder with full adders. The output sum should include the overflow bit.", "module_header": "module top_module (\n\tinput [3:0] x,\n\tinput [3:0] y,\n\toutput [4:0] sum\n);\n", "original_code": "module top_module (\n\tinput [3:0] x,\n\tinput [3:0] y,\n\toutput [4:0] sum\n);\n full_adder fa0(x[0], y[0], 1'b0, sum[0], c1);\n full_adder fa1(x[1], y[1], c1, sum[1], c2);\n full_adder fa2(x[2], y[2], c2, sum[2], c3);\n full_adder fa3(x[3], y[3], c3, sum[3], sum[4]);\n\nendmodule", "error": "6: error: Unknown module type: full_adder\n7: warning: implicit definition of wire 'c2'.\n8: warning: implicit definition of wire 'c3'.\n8: error: Unknown module type: full_adder\n9: error: Unknown module type: full_adder\n6: warning: implicit definition of wire 'c1'.\n7: error: Unknown module type: full_adder\n"} {"task_id": "m2014_q4k", "description": "Implement a shift register with four D flops. Reset is active-low synchronous resettable.", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput in,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput in,\n\toutput out\n);\n parameter N = 4; // number of D flip-flops\n reg [N-1:0] dff_out; // output of D flip-flops\n wire [N-2:0] shift_in; // input for shift register\n assign shift_in[0] = in; // input is shifted into output\n assign shift_in[1:N-1] = dff_out[0:N-2]; // shift register is shifted right\n assign out = dff_out[N-1]; // output is last D flip-flop output\n always @(posedge clk or negedge resetn) begin\n if (!resetn) begin\n dff_out <= {N{1'b0}}; // clear to zero\n end else begin\n dff_out <= {shift_in, in}; // shift input into output\n end\n end\n\nendmodule", "error": "11: error: part select dff_out[0:2] is out of order.\n11: : Did you mean shift_in[3:1]?\n11: warning: Part select shift_in[1:3] is out of range.\n11: error: Part select shift_in[1:3] indices reversed.\n"} {"task_id": "m2014_q4k", "description": "Implement a shift register with four D flops. Reset is active-low synchronous resettable.", "module_header": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput in,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput resetn,\n\tinput in,\n\toutput out\n);\n parameter WIDTH = 4;\n wire [WIDTH-1:0] data_in;\n wire [WIDTH-1:0] sr;\n assign data_in = {in,sr[WIDTH-2:0]};\n assign out = sr[WIDTH-1];\n\n reg_mult_dffe #(WIDTH) dff_4 (\n .clk(clk),\n .clrn(resetn),\n .d(data_in),\n .q(sr)\n );\n\nendmodule", "error": "13: error: Unknown module type: reg_mult_dffe\n"} {"task_id": "m2014_q6", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Implement this state machine in Verilog.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n parameter F = 2'b101;\n\n reg [2:0] state;\n reg [2:0] next_state;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= A;\n next_state <= B;\n end else begin\n state <= next_state;\n end\n end\n\n always @(*) begin\n case (state)\n A: begin\n if (w) begin\n next_state = B;\n end else begin\n next_state = C;\n end\n end\n B: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = E;\n end\n end\n C: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = E;\n end\n end\n D: begin\n if (w) begin\n next_state = F;\n end else begin\n next_state = E;\n end\n end\n E: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = E;\n end\n end\n F: begin\n if (w) begin\n next_state = F;\n end else begin\n next_state = E;\n end\n end\n endcase\n end\n\n assign z = (state == F && w);\n\nendmodule", "error": "12: warning: Numeric constant truncated to 2 bits.\n11: warning: Numeric constant truncated to 2 bits.\n11: warning: Extra digits given for sized binary constant.\n12: warning: Extra digits given for sized binary constant.\n"} {"task_id": "m2014_q6", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Implement this state machine in Verilog.", "module_header": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n", "original_code": "module top_module (\n\tinput clk,\n\tinput reset,\n\tinput w,\n\toutput z\n);\n parameter A = 2'b00;\n parameter B = 2'b01;\n parameter C = 2'b10;\n parameter D = 2'b11;\n parameter E = 2'b100;\n parameter F = 2'b101;\n\n reg [2:0] state, next_state;\n\n always @(posedge clk, posedge reset) begin\n if (reset) begin\n state <= A;\n end else begin\n state <= next_state;\n end\n end\n\n always @(*) begin\n case (state)\n A: begin\n if (w) begin\n next_state = A;\n end else begin\n next_state = B;\n end\n end\n B: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = C;\n end\n end\n C: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = E;\n end\n end\n D: begin\n if (w) begin\n next_state = A;\n end else begin\n next_state = F;\n end\n end\n E: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = E;\n end\n end\n F: begin\n if (w) begin\n next_state = D;\n end else begin\n next_state = F;\n end\n end\n endcase\n end\n\n assign z = (state == E);\n\nendmodule", "error": "12: warning: Numeric constant truncated to 2 bits.\n11: warning: Numeric constant truncated to 2 bits.\n11: warning: Extra digits given for sized binary constant.\n12: warning: Extra digits given for sized binary constant.\n"} {"task_id": "m2014_q6b", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Assume that you want to Implement the FSM using three flip-flops and state codes y[3:1] = 000, 001, ..., 101 for states A, B, ..., F, respectively. Implement just the next-state logic for y[2] in Verilog. The output Y2 is y[2].", "module_header": "module top_module(\n\tinput [3:1] y,\n\tinput w,\n\toutput reg Y2);\n", "original_code": "module top_module(\n\tinput [3:1] y,\n\tinput w,\n\toutput reg Y2);\n reg [1:0] next_state;\n always @ (y, w) begin\n case ({y[3:1], w})\n {0,0} : next_state = 2'b00;\n {0,1} : next_state = 2'b01;\n {1,0} : next_state = 2'b10;\n {1,1} : next_state = 2'b11;\n {2,0} : next_state = 2'b00;\n {2,1} : next_state = 2'b01;\n {3,0} : next_state = 2'b01;\n {3,1} : next_state = 2'b00;\n {4,0} : next_state = 2'b10;\n {4,1} : next_state = 2'b11;\n {5,0} : next_state = 2'b11;\n {5,1} : next_state = 2'b00;\n {6,0} : next_state = 2'b11;\n {6,1} : next_state = 2'b10;\n {7,0} : next_state = 2'b10;\n {7,1} : next_state = 2'b11;\n endcase\n end\n assign Y2 = next_state;\n endmodule", "error": "9: error: Concatenation operand \"'sd1\" has indefinite width.\n8: error: Concatenation operand \"'sd0\" has indefinite width.\n15: error: Concatenation operand \"'sd1\" has indefinite width.\n23: error: Concatenation operand \"'sd7\" has indefinite width.\n22: error: Concatenation operand \"'sd0\" has indefinite width.\n20: error: Concatenation operand \"'sd6\" has indefinite width.\n19: error: Concatenation operand \"'sd1\" has indefinite width.\n12: error: Concatenation operand \"'sd2\" has indefinite width.\n22: error: Concatenation operand \"'sd7\" has indefinite width.\n16: error: Concatenation operand \"'sd0\" has indefinite width.\n13: error: Concatenation operand \"'sd1\" has indefinite width.\n19: error: Concatenation operand \"'sd5\" has indefinite width.\n20: error: Concatenation operand \"'sd0\" has indefinite width.\n17: error: Concatenation operand \"'sd1\" has indefinite width.\n14: error: Concatenation operand \"'sd0\" has indefinite width.\n10: error: Concatenation operand \"'sd1\" has indefinite width.\n14: error: Concatenation operand \"'sd3\" has indefinite width.\n23: error: Concatenation operand \"'sd1\" has indefinite width.\n18: error: Concatenation operand \"'sd5\" has indefinite width.\n9: error: Concatenation operand \"'sd0\" has indefinite width.\n11: error: Concatenation operand \"'sd1\" has indefinite width.\n13: error: Concatenation operand \"'sd2\" has indefinite width.\n17: error: Concatenation operand \"'sd4\" has indefinite width.\n16: error: Concatenation operand \"'sd4\" has indefinite width.\n21: error: Concatenation operand \"'sd1\" has indefinite width.\n12: error: Concatenation operand \"'sd0\" has indefinite width.\n15: error: Concatenation operand \"'sd3\" has indefinite width.\n21: error: Concatenation operand \"'sd6\" has indefinite width.\n18: error: Concatenation operand \"'sd0\" has indefinite width.\n10: error: Concatenation operand \"'sd0\" has indefinite width.\n"} {"task_id": "m2014_q6b", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Assume that you want to Implement the FSM using three flip-flops and state codes y[3:1] = 000, 001, ..., 101 for states A, B, ..., F, respectively. Implement just the next-state logic for y[2] in Verilog. The output Y2 is y[2].", "module_header": "module top_module(\n\tinput [3:1] y,\n\tinput w,\n\toutput reg Y2);\n", "original_code": "module top_module(\n\tinput [3:1] y,\n\tinput w,\n\toutput reg Y2);\n\n always @ (y[2:0]) begin\n case (y[2:0])\n 3'b000: if (w) Y2=0; else Y2=1; //A --> A\n 3'b001: if (w) Y2=0; else Y2=1; //B --> D\n 3'b010: if (w) Y2=0; else Y2=1; //C --> E\n 3'b011: if (w) Y2=1; else Y2=0; //D --> A\n 3'b100: if (w) Y2=1; else Y2=0; //E --> D\n\tendcase\n\tend\n endmodule", "error": "7: warning: Part select [2:0] is selecting before the vector y[3:1].\n6: : Replacing the out of bound bits with 'bx.\n6: warning: Part select [2:0] is selecting before the vector y[3:1].\n7: : Replacing the out of bound bits with 'bx.\n"} {"task_id": "m2014_q6c", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Resets into state A. For this part, assume that a one-hot code is used with the state assignment y[6:1] = 000001, 000010, 000100, 001000, 010000, 100000 for states A, B,..., F, respectively.\n\n// Write Verilog for the next-state signals Y2 and Y4 corresponding to signal y[2] and y[4]. Derive the logic equations by inspection assuming a one-hot encoding. ", "module_header": "module top_module (\n\tinput [6:1] y,\n\tinput w,\n\toutput Y2,\n\toutput Y4\n);\n", "original_code": "module top_module (\n\tinput [6:1] y,\n\tinput w,\n\toutput Y2,\n\toutput Y4\n);\n assign Y2 = (y == 2'b000010) ? 1'b1 : 1'b0; // Next state of Y2 is B if current state is A and w=0\n assign Y4 = (y == 2'b000100) ? 1'b1 : // Next state of Y4 is C if current state is B and w=0\n (y == 2'b000001) ? 1'b1 : // Next state of Y4 is D if current state is A and w=1\n (y == 2'b001000) ? 1'b1 : // Next state of Y4 is E if current state is C and w=1\n (y == 2'b010000) ? 1'b1 : // Next state of Y4 is D if current state is F and w=1\n 1'b0; // Default value is 0\n\nendmodule", "error": "8: warning: Extra digits given for sized binary constant.\n10: warning: Extra digits given for sized binary constant.\n10: warning: Numeric constant truncated to 2 bits.\n11: warning: Extra digits given for sized binary constant.\n9: warning: Extra digits given for sized binary constant.\n11: warning: Numeric constant truncated to 2 bits.\n8: warning: Numeric constant truncated to 2 bits.\n7: warning: Extra digits given for sized binary constant.\n"} {"task_id": "m2014_q6c", "description": "Consider the state machine shown below:\n\n// A (0) --0--> B\n// A (0) --1--> A\n// B (0) --0--> C\n// B (0) --1--> D\n// C (0) --0--> E\n// C (0) --1--> D\n// D (0) --0--> F\n// D (0) --1--> A\n// E (1) --0--> E\n// E (1) --1--> D\n// F (1) --0--> C\n// F (1) --1--> D\n\n// Resets into state A. For this part, assume that a one-hot code is used with the state assignment y[6:1] = 000001, 000010, 000100, 001000, 010000, 100000 for states A, B,..., F, respectively.\n\n// Write Verilog for the next-state signals Y2 and Y4 corresponding to signal y[2] and y[4]. Derive the logic equations by inspection assuming a one-hot encoding. ", "module_header": "module top_module (\n\tinput [6:1] y,\n\tinput w,\n\toutput Y2,\n\toutput Y4\n);\n", "original_code": "module top_module (\n\tinput [6:1] y,\n\tinput w,\n\toutput Y2,\n\toutput Y4\n);\n parameter A = 6'b000001, B = 6'b000010, C = 6'b000100, D = 6'b001000, E = 6'b010000, F = 6'b100000;\n\n // verilator lint_off UNUSED\n wire [6:1] y0 = 6'b000001; // A\n wire [6:1] y1 = 6'b000010; // B\n wire [6:1] y2 = 6'b000100; // C\n wire [6:1] y3 = 6'b001000; // D\n wire [6:1] y4 = 6'b010000; // E\n wire [6:1] y5 = 6'b100000; // F\n wire [6:1] yx [6:1];\n // verilator lint_on UNUSED\n\n generate genvar i;\n for (i=1; i<6; i=i+1) begin : label_0\n assign yx[i] = ((i==1 & (!y[0] & y[1])) | (i==2 & (!y[2] & y[3])) | (i==3 & (!y[2] & y[4])) | (i==4 & (!y[0] & y[4])) | (i==5 & (!w & y[0])));\n end\n endgenerate\n\n assign Y2 = ((y0 & ~w) | (y5 & w));\n assign Y4 = ((y1 & ~w) | (y5 & ~w));\n\nendmodule", "error": "21: warning: Constant bit select [0] is before vector y[6:1].\n21: : Replacing select with a constant 1'bx.\n"} {"task_id": "mt2015_eq2", "description": "Create a circuit that has two 2-bit inputs A[1:0] and B[1:0], and produces an output z. The value of z should be 1 if A = B, otherwise z should be 0.", "module_header": "module top_module(\n\tinput [1:0] A,\n\tinput [1:0] B,\n\toutput z);\n", "original_code": "module top_module(\n\tinput [1:0] A,\n\tinput [1:0] B,\n\toutput z);\n\n\twire [1:0] and_result;\n\twire or_result;\n\n\t// Compare each bit of A and B using AND gates\n\tand_gate and0(and_result[0], A[0], B[0]);\n\tand_gate and1(and_result[1], A[1], B[1]);\n\n\t// Combine the results of the AND gates using an OR gate\n\tor_gate or0(or_result, and_result[0], and_result[1]);\n\n\t// Output the result of the OR gate\n\tassign z = or_result;\n\nendmodule", "error": "14: error: Unknown module type: or_gate\n11: error: Unknown module type: and_gate\n10: error: Unknown module type: and_gate\n"} {"task_id": "mt2015_eq2", "description": "Create a circuit that has two 2-bit inputs A[1:0] and B[1:0], and produces an output z. The value of z should be 1 if A = B, otherwise z should be 0.", "module_header": "module top_module(\n\tinput [1:0] A,\n\tinput [1:0] B,\n\toutput z);\n", "original_code": "module top_module(\n\tinput [1:0] A,\n\tinput [1:0] B,\n\toutput z);\nalways @(*) begin\n if(A == B)\n z = 1'b1;\n else\n z = 1'b0;\n end\n\n endmodule\n", "error": "9: error: 'z' is not a valid l-value for a procedural assignment.\n4: : 'z' is declared here as a wire.\n7: error: 'z' is not a valid l-value for a procedural assignment.\n"} {"task_id": "mt2015_muxdff", "description": "Consider this Verilog module \"full_module\":\n\n// module full_module (\n// input [2:0] r,\n// input L,\n// input clk,\n// output reg [2:0] q\n);\n\n// always @(posedge clk) begin\n// if (L) begin\n// q <= r;\n// end else begin\n// q <= {q[1] ^ q[2], q[0], q[2]};\n// end\n// end\n\n// endmodule\n\n// You want to create a hierarchical Verilog design where a flipflop and 2-1 multiplexer are in a submodule, and that submodule is instantiated three times in this code. Create the submodule called \"top_module\".\n", "module_header": "module top_module(\n\tinput clk,\n\tinput L,\n\tinput q_in,\n\tinput r_in,\n\toutput reg Q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput L,\n\tinput q_in,\n\tinput r_in,\n\toutput reg Q);\n always @(posedge clk) begin\n if (L) begin\n Q <= r_in;\n end else begin\n Q <= {q_in[1], q_in[0], q_in[2], q_in[3]};\n end\n end\n\nendmodule", "error": "11: error: can not select part of scalar: q_in\n11: error: Concatenation/replication may not have zero width in this context.\n"} {"task_id": "mt2015_muxdff", "description": "Consider this Verilog module \"full_module\":\n\n// module full_module (\n// input [2:0] r,\n// input L,\n// input clk,\n// output reg [2:0] q\n);\n\n// always @(posedge clk) begin\n// if (L) begin\n// q <= r;\n// end else begin\n// q <= {q[1] ^ q[2], q[0], q[2]};\n// end\n// end\n\n// endmodule\n\n// You want to create a hierarchical Verilog design where a flipflop and 2-1 multiplexer are in a submodule, and that submodule is instantiated three times in this code. Create the submodule called \"top_module\".\n", "module_header": "module top_module(\n\tinput clk,\n\tinput L,\n\tinput q_in,\n\tinput r_in,\n\toutput reg Q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput L,\n\tinput q_in,\n\tinput r_in,\n\toutput reg Q);\n parameter n=3;\n parameter m=4;\n\n\t// Define flipflop\n\treg [0:0] ff_out;\n\talways @(posedge clk) begin\n\t if (L) begin\n\t ff_out <= q_in;\n\t end else begin\n\t ff_out <= {ff_out[0] ^ ff_out[1], ff_out[0], ff_out[1]};\n\t end\n\tend\n\n\t// Define 2-1 multiplexer\n\twire [0:0] mux_out;\n\tassign mux_out = (L) ? r_in : ff_out;\n\n\t// Instantiate full_module 3 times\n\treg [2:0] q1, q2, q3;\n\tfull_module module1(.r(r_in), .L(L), .clk(clk), .q(q1));\n\tfull_module module2(.r(q1), .L(L), .clk(clk), .q(q2));\n\tfull_module module3(.r(q2), .L(L), .clk(clk), .q(q3));\n\n\t// Output final value\n\talways @(posedge clk) begin\n\t Q <= q3[2];\n\tend\n\nendmodule", "error": "28: error: Unknown module type: full_module\n26: error: Unknown module type: full_module\n27: error: Unknown module type: full_module\n"} {"task_id": "mt2015_q4", "description": "Module A implements the boolean function z = (x^y) & x.\n\n// Module B can be described by the following simulation waveform: \n\n// time x y z \n// 0ns 0 0 1 \n// 5ns 0 0 1 \n// 10ns 0 0 1 \n// 15ns 0 0 1 \n// 20ns 0 0 1 \n// 25ns 1 0 0 \n// 30ns 1 0 0 \n// 35ns 0 1 0 \n// 40ns 0 1 0 \n// 45ns 1 1 1 \n// 50ns 1 1 1 \n// 55ns 0 0 1 \n// 60ns 0 1 0 \n// 65ns 0 1 0 \n// 70ns 1 1 1 \n// 75ns 0 1 0 \n// 80ns 0 1 0 \n// 85ns 0 1 0 \n// 90ns 1 0 0 \n\n\n// Now consider a top-level that uses two A submodules and two B submodules. The first input of all four submodules is connect to input 'x', and the second input of all four submodules is connected to 'y'. The output of the first A submodule is connected to a two-input OR, along with the output of the first B submodule. The second pair of A and B submodules is similarly connected to an AND gate. The output of the OR and the AND is connected to an XOR, whose output is 'z'.\n\n// Implement this circuit in Verilog.", "module_header": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n", "original_code": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n // Instantiate submodule A\n wire a_out1;\n wire a_out2;\n A a_inst1(.x(x), .y(y), .z1(a_out1), .z2(a_out2));\n\n // Instantiate submodule B\n wire b_out;\n B b_inst(.x(x), .y(y), .z(b_out));\n\n // Connect inputs to submodules\n assign a_inst1.x = x;\n assign a_inst1.y = y;\n assign b_inst.x = x;\n assign b_inst.y = y;\n\n // Perform logical operations\n assign z = (a_out1 | b_out) & (a_out2 & b_out);\n\nendmodule", "error": "12: error: Unknown module type: B\n8: error: Unknown module type: A\n"} {"task_id": "mt2015_q4", "description": "Module A implements the boolean function z = (x^y) & x.\n\n// Module B can be described by the following simulation waveform: \n\n// time x y z \n// 0ns 0 0 1 \n// 5ns 0 0 1 \n// 10ns 0 0 1 \n// 15ns 0 0 1 \n// 20ns 0 0 1 \n// 25ns 1 0 0 \n// 30ns 1 0 0 \n// 35ns 0 1 0 \n// 40ns 0 1 0 \n// 45ns 1 1 1 \n// 50ns 1 1 1 \n// 55ns 0 0 1 \n// 60ns 0 1 0 \n// 65ns 0 1 0 \n// 70ns 1 1 1 \n// 75ns 0 1 0 \n// 80ns 0 1 0 \n// 85ns 0 1 0 \n// 90ns 1 0 0 \n\n\n// Now consider a top-level that uses two A submodules and two B submodules. The first input of all four submodules is connect to input 'x', and the second input of all four submodules is connected to 'y'. The output of the first A submodule is connected to a two-input OR, along with the output of the first B submodule. The second pair of A and B submodules is similarly connected to an AND gate. The output of the OR and the AND is connected to an XOR, whose output is 'z'.\n\n// Implement this circuit in Verilog.", "module_header": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n", "original_code": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n // Instantiate two A submodules and two B submodules\n A a1(x, y, z1);\n A a2(x, y, z2);\n B b1(x, y, z3);\n B b2(x, y, z4);\n\n // Connect the outputs of the A submodules to an OR gate\n assign or_out = z1 | z2;\n\n // Connect the outputs of the B submodules to an AND gate\n assign and_out = z3 & z4;\n\n // Connect the outputs of the OR and AND gates to an XOR gate\n assign z = or_out ^ and_out;\n\n\tendmodule", "error": "6: warning: implicit definition of wire 'z1'.\n8: warning: implicit definition of wire 'z3'.\n7: warning: implicit definition of wire 'z2'.\n9: error: Unknown module type: B\n7: error: Unknown module type: A\n8: error: Unknown module type: B\n15: warning: implicit definition of wire 'and_out'.\n6: error: Unknown module type: A\n12: warning: implicit definition of wire 'or_out'.\n9: warning: implicit definition of wire 'z4'.\n"} {"task_id": "mt2015_q4b", "description": "The module can be described by the following simulation waveform: \n\n// time x y z \n// 0ns 0 0 1 \n// 5ns 0 0 1 \n// 10ns 0 0 1 \n// 15ns 0 0 1 \n// 20ns 0 0 1 \n// 25ns 1 0 0 \n// 30ns 1 0 0 \n// 35ns 0 1 0 \n// 40ns 0 1 0 \n// 45ns 1 1 1 \n// 50ns 1 1 1 \n// 55ns 0 0 1 \n// 60ns 0 1 0 \n// 65ns 0 1 0 \n// 70ns 1 1 1 \n// 75ns 0 1 0 \n// 80ns 0 1 0 \n// 85ns 0 1 0 \n// 90ns 1 0 0 ", "module_header": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n", "original_code": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n // Initial state of z is 1\n reg z = 1'b1;\n\n // Counter to keep track of time in current state\n reg [31:0] counter = 0;\n\n // State machine to handle input sequence\n always @(x or y) begin\n // Reset counter if in default state\n if (x == 0 && y == 0) begin\n counter <= 0;\n end else begin\n // Increment counter for current state\n counter <= counter + 1;\n end\n\n // Check for single input high\n if ((x == 1 && y == 0) || (x == 0 && y == 1)) begin\n z <= 1'b0;\n end else if (x == 1 && y == 1) begin\n // Reset counter if both inputs are high\n counter <= 0;\n z <= 1'b1;\n end else begin\n // Maintain current state if no conditions met\n z <= z;\n end\n end\n\n // Reset z to 1 after 20ns of default state\n always @(counter) begin\n if (counter >= 20) begin\n z <= 1'b1;\n end\n end\n\nendmodule", "error": "4: : It was declared here as a net.\n6: error: 'z' has already been declared in this scope.\n"} {"task_id": "mt2015_q4b", "description": "The module can be described by the following simulation waveform: \n\n// time x y z \n// 0ns 0 0 1 \n// 5ns 0 0 1 \n// 10ns 0 0 1 \n// 15ns 0 0 1 \n// 20ns 0 0 1 \n// 25ns 1 0 0 \n// 30ns 1 0 0 \n// 35ns 0 1 0 \n// 40ns 0 1 0 \n// 45ns 1 1 1 \n// 50ns 1 1 1 \n// 55ns 0 0 1 \n// 60ns 0 1 0 \n// 65ns 0 1 0 \n// 70ns 1 1 1 \n// 75ns 0 1 0 \n// 80ns 0 1 0 \n// 85ns 0 1 0 \n// 90ns 1 0 0 ", "module_header": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n", "original_code": "module top_module(\n\tinput x,\n\tinput y,\n\toutput z);\n// Initial state of z is 1\n reg z = 1'b1;\n\n // Counter to keep track of time in current state\n reg [31:0] counter = 0;\n\n // State machine to handle input sequence\n always @(x or y) begin\n // Reset counter if in default state\n if (x == 0 && y == 0) begin\n counter <= 0;\n end else begin\n // Increment counter for current state\n counter <= counter + 1;\n end\n\n // Check for single input high\n if ((x == 1 && y == 0) || (x == 0 && y == 1)) begin\n z <= 1'b0;\n end else if (x == 1 && y == 1) begin\n // Reset counter if both inputs are high\n counter <= 0;\n z <= 1'b1;\n end else begin\n // Maintain current state if no conditions met\n z <= z;\n end\n end\n\n // Reset z to 1 after 20ns of default state\n always @(counter) begin\n if (counter >= 20) begin\n z <= 1'b1;\n end\n end\n\nendmodule\n", "error": "4: : It was declared here as a net.\n6: error: 'z' has already been declared in this scope.\n"} {"task_id": "mux256to1", "description": "Create a 1-bit wide, 256-to-1 multiplexer. The 256 inputs are all packed into a single 256-bit input vector. sel=0 should select in[0], sel=1 selects bits in[1], sel=2 selects bits in[2], etc.", "module_header": "module top_module (\n\tinput [255:0] in,\n\tinput [7:0] sel,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput [255:0] in,\n\tinput [7:0] sel,\n\toutput out\n);\n assign out = insel;\n\nendmodule", "error": "6: error: Unable to bind wire/reg/memory `insel' in `top_module'\n6: error: Unable to elaborate r-value: insel\n"} {"task_id": "mux256to1", "description": "Create a 1-bit wide, 256-to-1 multiplexer. The 256 inputs are all packed into a single 256-bit input vector. sel=0 should select in[0], sel=1 selects bits in[1], sel=2 selects bits in[2], etc.", "module_header": "module top_module (\n\tinput [255:0] in,\n\tinput [7:0] sel,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput [255:0] in,\n\tinput [7:0] sel,\n\toutput out\n);\n\treg out;\n\t\n\talways @(*)\n\tbegin\n\t\tcase(sel)\n\t\t\t8'b00000001: out = in[0];\n\t\t\t8'b00000010: out = in[1];\n\t\t\t8'b00000100: out = in[2];\n\t\t\t8'b00001000: out = in[3];\n\t\t\t8'b00010000: out = in[4];\n\t\t\t8'b00100000: out = in[5];\n\t\t\t8'b01000000: out = in[6];\n\t\t\t8'b10000000: out = in[7];\n\t\t\t8'b00000001: out = in[8];\n\t\t\t8'b00000010: out = in[9];\n\t\t\t8'b00000100: out = in[10];\n\t\t\t8'b00001000: out = in[11];\n\t\t\t8'b00010000: out = in[12];\n\t\t\t8'b00100000: out = in[13];\n\t\t\t8'b01000000: out = in[14];\n\t\t\t8'b10000000: out = in[15];\n\t\t\tdefault: out = 1'b0;\n\t\tendcase\n\tend\n\nendmodule", "error": "4: : It was declared here as a net.\n6: error: 'out' has already been declared in this scope.\n"} {"task_id": "mux256to1v", "description": "Create a 4-bit wide, 256-to-1 multiplexer. The 256 4-bit inputs are all packed into a single 1024-bit input vector. sel=0 should select bits in[3:0], sel=1 selects bits in[7:4], sel=2 selects bits in[11:8], etc.", "module_header": "module top_module (\n\tinput [1023:0] in,\n\tinput [7:0] sel,\n\toutput [3:0] out\n);\n", "original_code": "module top_module (\n\tinput [1023:0] in,\n\tinput [7:0] sel,\n\toutput [3:0] out\n);\n assign out = in[(sel*4)+3 : (sel*4)];\n\nendmodule", "error": "6: error: Part select expressions must be constant integral values.\n6: : The msb expression violates that rule: ((sel)*('sd4))+('sd3)\n6: error: A reference to a net or variable (`sel') is not allowed in a constant expression.\n6: : The lsb expression violates that rule: (sel)*('sd4)\n"} {"task_id": "mux256to1v", "description": "Create a 4-bit wide, 256-to-1 multiplexer. The 256 4-bit inputs are all packed into a single 1024-bit input vector. sel=0 should select bits in[3:0], sel=1 selects bits in[7:4], sel=2 selects bits in[11:8], etc.", "module_header": "module top_module (\n\tinput [1023:0] in,\n\tinput [7:0] sel,\n\toutput [3:0] out\n);\n", "original_code": "module top_module (\n\tinput [1023:0] in,\n\tinput [7:0] sel,\n\toutput [3:0] out\n);\n assign out = in[(sel*4)+3:(sel*4)];\n\nendmodule", "error": "6: error: Part select expressions must be constant integral values.\n6: : The msb expression violates that rule: ((sel)*('sd4))+('sd3)\n6: error: A reference to a net or variable (`sel') is not allowed in a constant expression.\n6: : The lsb expression violates that rule: (sel)*('sd4)\n"} {"task_id": "mux2to1", "description": "Create a one-bit wide, 2-to-1 multiplexer. When sel=0, choose a. When sel=1, choose b.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput sel,\n\toutput out\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput sel,\n\toutput out\n);\nalways @(*) begin\n\tif (sel == 1'b0) \n\t\tout = a;\n\telse \n\t\tout = b;\nend\n\nendmodule\n", "error": "11: error: 'out' is not a valid l-value for a procedural assignment.\n5: : 'out' is declared here as a wire.\n9: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "mux2to1v", "description": "Create a 2-1 multiplexer. When sel=0, choose a. When sel=1, choose b.", "module_header": "module top_module (\n\tinput [99:0] a,\n\tinput [99:0] b,\n\tinput sel,\n\toutput [99:0] out\n);\n", "original_code": "module top_module (\n\tinput [99:0] a,\n\tinput [99:0] b,\n\tinput sel,\n\toutput [99:0] out\n);\n always @(*) begin\n if (sel == 1'b0) begin\n out = a;\n end else begin\n out = b;\n end\n end\n\nendmodule", "error": "11: error: 'out' is not a valid l-value for a procedural assignment.\n5: : 'out' is declared here as a wire.\n9: error: 'out' is not a valid l-value for a procedural assignment.\n"} {"task_id": "norgate", "description": "Create a module that implements a NOR gate.", "module_header": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n", "original_code": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n sky130_fd_sc_hd__nor2b base(\n\t .A(a),\n\t .B(b),\n\t .OUT(out)\n );\n\n endmodule", "error": "6: error: Unknown module type: sky130_fd_sc_hd__nor2b\n"} {"task_id": "norgate", "description": "Create a module that implements a NOR gate.", "module_header": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n", "original_code": "module top_module(\n\tinput a, \n\tinput b,\n\toutput out\n);\n sky130_fd_sc_hdll__nor2b nor_gate(\n .A(a),\n .B(b),\n .Y(out)\n );\n\nendmodule", "error": "6: error: Unknown module type: sky130_fd_sc_hdll__nor2b\n"} {"task_id": "notgate", "description": "Create a module that implements a NOT gate.", "module_header": "module top_module(\n\tinput in,\n\toutput out\n);\n", "original_code": "module top_module(\n\tinput in,\n\toutput out\n);\nreg out;\n\nalways @(posedge clk or posedge reset)\nbegin\n\tif(reset)\n\t\tout <= 1'b0;\n\telse\n\t\tout <= w;\nend\n\nassign z = out;\n\nendmodule\n", "error": "15: warning: implicit definition of wire 'z'.\n5: error: 'out' has already been declared in this scope.\n3: : It was declared here as a net.\n"} {"task_id": "popcount255", "description": "A \"population count\" circuit counts the number of '1's in an input vector. Build a population count circuit for a 255-bit input vector.", "module_header": "module top_module (\n\tinput [254:0] in,\n\toutput reg [7:0] out\n);\n", "original_code": "module top_module (\n\tinput [254:0] in,\n\toutput reg [7:0] out\n);\n // 255-bit input vector\n // 8-bit output vector\n\n // 8-bit adder for each 32-bit chunk\n wire [7:0] adder0, adder1, adder2, adder3, adder4, adder5, adder6, adder7;\n\n // 32-bit chunks of the input vector\n wire [31:0] chunk0, chunk1, chunk2, chunk3, chunk4, chunk5, chunk6, chunk7;\n\n // 8-bit chunks of the output vector\n wire [7:0] chunk0_out, chunk1_out, chunk2_out, chunk3_out, chunk4_out, chunk5_out, chunk6_out, chunk7_out;\n\n // Split the input vector into 8 32-bit chunks\n assign chunk0 = in[31:0];\n assign chunk1 = in[63:32];\n assign chunk2 = in[95:64];\n assign chunk3 = in[127:96];\n assign chunk4 = in[159:128];\n assign chunk5 = in[191:160];\n assign chunk6 = in[223:192];\n assign chunk7 = in[255:224];\n\n // Count the number of '1's in each 32-bit chunk\n assign chunk0_out = chunk0 ^ (chunk0 >> 1);\n assign chunk1_out = chunk1 ^ (chunk1 >> 1);\n assign chunk2_out = chunk2 ^ (chunk2 >> 1);\n assign chunk3_out = chunk3 ^ (chunk3 >> 1);\n assign chunk4_out = chunk4 ^ (chunk4 >> 1);\n assign chunk5_out = chunk5 ^ (chunk5 >> 1);\n assign chunk6_out = chunk6 ^ (chunk6 >> 1);\n assign chunk7_out = chunk7 ^ (chunk7 >> 1);\n\n // Add the counts from each 32-bit chunk\n assign adder0 = chunk0_out[0] + chunk1_out[0] + chunk2_out[0] + chunk3_out[0] + chunk4_out[0] + chunk5_out[0] + chunk6_out[0] + chunk7_out[0];\n assign adder1 = chunk0_out[1] + chunk1_out[1] + chunk2_out[1] + chunk3_out[1] + chunk4_out[1] + chunk5_out[1] + chunk6_out[1] + chunk7_out[1];\n assign adder2 = chunk0_out[2] + chunk1_out[2] + chunk2_out[2] + chunk3_out[2] + chunk4_out[2] + chunk5_out[2] + chunk6_out[2] + chunk7_out[2];\n assign adder3 = chunk0_out[3] + chunk1_out[3] + chunk2_out[3] + chunk3_out[3] + chunk4_out[3] + chunk5_out[3] + chunk6_out[3] + chunk7_out[3];\n assign adder4 = chunk0_out[4] + chunk1_out[4] + chunk2_out[4] + chunk3_out[4] + chunk4_out[4] + chunk5_out[4] + chunk6_out[4] + chunk7_out[4];\n assign adder5 = chunk0_out[5] + chunk1_out[5] + chunk2_out[5] + chunk3_out[5] + chunk4_out[5] + chunk5_out[5] + chunk6_out[5] + chunk7_out[5];\n assign adder6 = chunk0_out[6] + chunk1_out[6] + chunk2_out[6] + chunk3_out[6] + chunk4_out[6] + chunk5_out[6] + chunk6_out[6] + chunk7_out[6];\n assign adder7 = chunk0_out[7] + chunk1_out[7] + chunk2_out[7] + chunk3_out[7] + chunk4_out[7] + chunk5_out[7] + chunk6_out[7] + chunk7_out[7];\n\n // Output the sum of the counts from each 32-bit chunk\n assign out = adder0 + adder1 + adder2 + adder3 + adder4 + adder5 + adder6 + adder7;\n\nendmodule", "error": "25: warning: Part select [255:224] is selecting after the vector in[254:0].\n25: : Replacing the out of bound bits with 'bx.\n"} {"task_id": "popcount255", "description": "A \"population count\" circuit counts the number of '1's in an input vector. Build a population count circuit for a 255-bit input vector.", "module_header": "module top_module (\n\tinput [254:0] in,\n\toutput reg [7:0] out\n);\n", "original_code": "module top_module (\n\tinput [254:0] in,\n\toutput reg [7:0] out\n);\n // 255-bit input vector\n // 8-bit output vector\n\n // 8-bit adder for each 32-bit chunk\n wire [7:0] adder_out [7:0];\n\n // 32-bit chunks of the input vector\n wire [31:0] chunk [7:0];\n\n // Split the input vector into 32-bit chunks\n assign chunk[0] = in[31:0];\n assign chunk[1] = in[63:32];\n assign chunk[2] = in[95:64];\n assign chunk[3] = in[127:96];\n assign chunk[4] = in[159:128];\n assign chunk[5] = in[191:160];\n assign chunk[6] = in[223:192];\n assign chunk[7] = in[255:224];\n\n // Add up the '1's in each chunk\n assign adder_out[0] = chunk[0] + chunk[1] + chunk[2] + chunk[3] + chunk[4] + chunk[5] + chunk[6] + chunk[7];\n assign adder_out[1] = chunk[8] + chunk[9] + chunk[10] + chunk[11] + chunk[12] + chunk[13] + chunk[14] + chunk[15];\n assign adder_out[2] = chunk[16] + chunk[17] + chunk[18] + chunk[19] + chunk[20] + chunk[21] + chunk[22] + chunk[23];\n assign adder_out[3] = chunk[24] + chunk[25] + chunk[26] + chunk[27] + chunk[28] + chunk[29] + chunk[30] + chunk[31];\n assign adder_out[4] = chunk[32] + chunk[33] + chunk[34] + chunk[35] + chunk[36] + chunk[37] + chunk[38] + chunk[39];\n assign adder_out[5] = chunk[40] + chunk[41] + chunk[42] + chunk[43] + chunk[44] + chunk[45] + chunk[46] + chunk[47];\n assign adder_out[6] = chunk[48] + chunk[49] + chunk[50] + chunk[51] + chunk[52] + chunk[53] + chunk[54] + chunk[55];\n assign adder_out[7] = chunk[56] + chunk[57] + chunk[58] + chunk[59] + chunk[60] + chunk[61] + chunk[62] + chunk[63];\n\n // Output the sum of the '1's in each chunk\n always @(*) begin\n // always block triggered whenever there is a change in any of the inputs\n out = adder_out[0] + adder_out[1] + adder_out[2] + adder_out[3] + adder_out[4] + adder_out[5] + adder_out[6] + adder_out[7];\n end\n\nendmodule", "error": "32: warning: returning 'bx for out of bounds array access chunk[57].\n26: warning: returning 'bx for out of bounds array access chunk[9].\n32: warning: returning 'bx for out of bounds array access chunk[62].\n28: warning: returning 'bx for out of bounds array access chunk[29].\n26: warning: returning 'bx for out of bounds array access chunk[10].\n26: warning: returning 'bx for out of bounds array access chunk[15].\n26: warning: returning 'bx for out of bounds array access chunk[14].\n30: warning: returning 'bx for out of bounds array access chunk[44].\n30: warning: returning 'bx for out of bounds array access chunk[47].\n31: warning: returning 'bx for out of bounds array access chunk[55].\n31: warning: returning 'bx for out of bounds array access chunk[50].\n32: warning: returning 'bx for out of bounds array access chunk[60].\n28: warning: returning 'bx for out of bounds array access chunk[27].\n37: warning: @* is sensitive to all 8 words in array 'adder_out'.\n30: warning: returning 'bx for out of bounds array access chunk[42].\n29: warning: returning 'bx for out of bounds array access chunk[38].\n32: warning: returning 'bx for out of bounds array access chunk[59].\n26: warning: returning 'bx for out of bounds array access chunk[13].\n27: warning: returning 'bx for out of bounds array access chunk[21].\n31: warning: returning 'bx for out of bounds array access chunk[54].\n28: warning: returning 'bx for out of bounds array access chunk[28].\n26: warning: returning 'bx for out of bounds array access chunk[11].\n29: warning: returning 'bx for out of bounds array access chunk[33].\n29: warning: returning 'bx for out of bounds array access chunk[35].\n31: warning: returning 'bx for out of bounds array access chunk[48].\n31: warning: returning 'bx for out of bounds array access chunk[52].\n26: warning: returning 'bx for out of bounds array access chunk[12].\n29: warning: returning 'bx for out of bounds array access chunk[34].\n27: warning: returning 'bx for out of bounds array access chunk[17].\n32: warning: returning 'bx for out of bounds array access chunk[61].\n26: warning: returning 'bx for out of bounds array access chunk[8].\n31: warning: returning 'bx for out of bounds array access chunk[53].\n27: warning: returning 'bx for out of bounds array access chunk[22].\n29: warning: returning 'bx for out of bounds array access chunk[39].\n28: warning: returning 'bx for out of bounds array access chunk[31].\n32: warning: returning 'bx for out of bounds array access chunk[63].\n31: warning: returning 'bx for out of bounds array access chunk[49].\n27: warning: returning 'bx for out of bounds array access chunk[20].\n27: warning: returning 'bx for out of bounds array access chunk[16].\n28: warning: returning 'bx for out of bounds array access chunk[30].\n29: warning: returning 'bx for out of bounds array access chunk[32].\n30: warning: returning 'bx for out of bounds array access chunk[40].\n28: warning: returning 'bx for out of bounds array access chunk[26].\n22: warning: Part select [255:224] is selecting after the vector in[254:0].\n28: warning: returning 'bx for out of bounds array access chunk[25].\n29: warning: returning 'bx for out of bounds array access chunk[36].\n27: warning: returning 'bx for out of bounds array access chunk[23].\n30: warning: returning 'bx for out of bounds array access chunk[41].\n32: warning: returning 'bx for out of bounds array access chunk[56].\n22: : Replacing the out of bound bits with 'bx.\n27: warning: returning 'bx for out of bounds array access chunk[18].\n28: warning: returning 'bx for out of bounds array access chunk[24].\n29: warning: returning 'bx for out of bounds array access chunk[37].\n30: warning: returning 'bx for out of bounds array access chunk[45].\n32: warning: returning 'bx for out of bounds array access chunk[58].\n30: warning: returning 'bx for out of bounds array access chunk[43].\n31: warning: returning 'bx for out of bounds array access chunk[51].\n27: warning: returning 'bx for out of bounds array access chunk[19].\n30: warning: returning 'bx for out of bounds array access chunk[46].\n"} {"task_id": "popcount3", "description": "A \"population count\" circuit counts the number of '1's in an input vector. Build a population count circuit for a 3-bit input vector.", "module_header": "module top_module (\n\tinput [2:0] in,\n\toutput [1:0] out\n);\n", "original_code": "module top_module (\n\tinput [2:0] in,\n\toutput [1:0] out\n);\n assign out = {in0 & in1 & in2, in0 & in1 | in0 & in2 | in1 & in2};\n\nendmodule", "error": "5: error: Unable to bind wire/reg/memory `in0' in `top_module'\n5: error: Unable to bind wire/reg/memory `in2' in `top_module'\n5: error: Unable to elaborate r-value: {((in0)&(in1))&(in2), (((in0)&(in1))|((in0)&(in2)))|((in1)&(in2))}\n5: error: Unable to bind wire/reg/memory `in1' in `top_module'\n5: error: Concatenation/replication may not have zero width in this context.\n"} {"task_id": "popcount3", "description": "A \"population count\" circuit counts the number of '1's in an input vector. Build a population count circuit for a 3-bit input vector.", "module_header": "module top_module (\n\tinput [2:0] in,\n\toutput [1:0] out\n);\n", "original_code": "module top_module (\n\tinput [2:0] in,\n\toutput [1:0] out\n);\n assign out[1:0] = $popcount(in);\n\nendmodule", "error": "5: error: System function $popcount not defined in system table or SFT file(s).\n5: internal error: Failed to synthesize expression: $popcount(in[2:0])\n"} {"task_id": "reduction", "description": "Parity checking is often used as a simple method of detecting errors when transmitting data through an imperfect channel. Create a circuit that will compute a parity bit for a 8-bit byte (which will add a 9th bit to the byte). We will use \"even\" parity, where the parity bit is just the XOR of all 8 data bits.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput parity\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput parity\n);\n parity_bit parity_bit_inst(\n .in(in),\n .parity(parity)\n );\n\nendmodule", "error": "5: error: Unknown module type: parity_bit\n"} {"task_id": "review2015_count1k", "description": "Build a counter that counts from 0 to 999, inclusive, with a period of 1000 cycles. The reset input is active high synchronous, and should reset the counter to 0.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [9:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [9:0] q);\n assign q = (count == 999) ? 0 : count + 1;\n\n always @(posedge clk, posedge reset) begin\n if (reset)\n count <= 0;\n else if (count == 999)\n count <= 0;\n else\n count <= count + 1;\n end\n\nendmodule", "error": "5: error: Unable to elaborate r-value: ((count)==('sd999))?('sd0):((count)+('sd1))\n10: error: Unable to bind wire/reg/memory `count' in `top_module'\n5: error: Unable to bind wire/reg/memory `count' in `top_module'\n10: error: Unable to elaborate condition expression.\n9: error: Could not find variable ``count'' in ``top_module''\n"} {"task_id": "review2015_count1k", "description": "Build a counter that counts from 0 to 999, inclusive, with a period of 1000 cycles. The reset input is active high synchronous, and should reset the counter to 0.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [9:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput reg [9:0] q);\n counter counter_inst (\n\t .clk(clk),\n\t .reset(reset),\n\t .q(q));\n\n always @(posedge clk) begin\n if (reset) begin\n q <= 10'b0;\n end else if (q == 10'd999) begin\n q <= 10'b0;\n end else begin\n q <= q + 10'b1;\n end\n end\n\nendmodule", "error": "5: error: Unknown module type: counter\n"} {"task_id": "review2015_fancytimer", "description": "We want to create a timer with one input that:\n\n// (1) is started when a particular input pattern (1101) is detected,\n// (2) shifts in 4 more bits to determine the duration to delay,\n// (3) waits for the counters to finish counting, and\n// (4) notifies the user and waits for the user to acknowledge the timer.\n\n// The serial data is available on the data input pin. When the pattern 1101 is received, the circuit must then shift in the next 4 bits, most-significant-bit first. These 4 bits determine the duration of the timer delay, referred to as delay[3:0]. After that, the state machine asserts its counting output to indicate it is counting. Once the 1101 and delay[3:0] have been read, the circuit no longer looks at the data input until it resumes searching after everything else is done.\n\n// The state machine must count for exactly (delay[3:0] + 1) * 1000 clock cycles. e.g., delay=0 means count 1000 cycles, and delay=5 means count 6000 cycles. Also output the current remaining time. This should be equal to delay for 1000 cycles, then delay-1 for 1000 cycles, and so on until it is 0 for 1000 cycles. \n\n// When the circuit isn't counting, the count[3:0] output is don't-care (whatever value is convenient for you to implement). At that point, the circuit must assert done to notify the user the timer has timed out, and waits until input ack is 1 before being reset to look for the next occurrence of the start sequence (1101).\n\n// The circuit should reset into a state where it begins searching for the input sequence 1101. The reset signal is active high synchronous. \n", "module_header": "module top_module(\n\tinput wire clk,\n\tinput wire reset,\n\tinput wire data,\n output wire [3:0] count,\n output reg counting,\n output reg done,\n input wire ack );\n", "original_code": "module top_module(\n\tinput wire clk,\n\tinput wire reset,\n\tinput wire data,\n output wire [3:0] count,\n output reg counting,\n output reg done,\n input wire ack );\n parameter IDLE=0, SEARCH=1, SHIFT=2, COUNT=3;\n\n reg [3:0] duration;\n reg [15:0] counter;\n reg [1:0] state;\n\n reg [3:0] current_count;\n wire [3:0] next_count;\n\n assign next_count = current_count - 1;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= IDLE;\n counter <= 0;\n current_count <= 0;\n counting <= 0;\n done <= 0;\n end else begin\n case(state)\n IDLE: begin\n if (data == 0) begin\n state <= SEARCH;\n end\n end\n SEARCH: begin\n if (data == 1 && counter == 1 && duration == 0) begin\n state <= SHIFT;\n counter <= 0;\n end else begin\n counter <= counter + 1;\n end\n end\n SHIFT: begin\n duration <= {data, duration[3:1]};\n counter <= 0;\n state <= COUNT;\n current_count <= duration + 1;\n counting <= 1;\n end\n COUNT: begin\n if (counter == 0 && current_count == 0) begin\n state <= IDLE;\n counting <= 0;\n done <= 1;\n end else if (counter == 0 && current_count != 0) begin\n current_count <= next_count;\n counter <= duration;\n end else begin\n counter <= counter - 1;\n end\n end\n endcase\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n count <= 0;\n end else begin\n if (counting) begin\n count <= current_count;\n end else begin\n count <= 0;\n end\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n counting <= 0;\n done <= 0;\n end else begin\n if (counting && ack) begin\n counting <= 0;\n done <= 0;\n end else if (state == IDLE && !counting) begin\n counting <= 0;\n done <= 0;\n end\n end\n end\n\n endmodule", "error": "5: : 'count' is declared here as a wire.\n67: error: 'count' is not a valid l-value for a procedural assignment.\n72: error: 'count' is not a valid l-value for a procedural assignment.\n70: error: 'count' is not a valid l-value for a procedural assignment.\n"} {"task_id": "review2015_fancytimer", "description": "We want to create a timer with one input that:\n\n// (1) is started when a particular input pattern (1101) is detected,\n// (2) shifts in 4 more bits to determine the duration to delay,\n// (3) waits for the counters to finish counting, and\n// (4) notifies the user and waits for the user to acknowledge the timer.\n\n// The serial data is available on the data input pin. When the pattern 1101 is received, the circuit must then shift in the next 4 bits, most-significant-bit first. These 4 bits determine the duration of the timer delay, referred to as delay[3:0]. After that, the state machine asserts its counting output to indicate it is counting. Once the 1101 and delay[3:0] have been read, the circuit no longer looks at the data input until it resumes searching after everything else is done.\n\n// The state machine must count for exactly (delay[3:0] + 1) * 1000 clock cycles. e.g., delay=0 means count 1000 cycles, and delay=5 means count 6000 cycles. Also output the current remaining time. This should be equal to delay for 1000 cycles, then delay-1 for 1000 cycles, and so on until it is 0 for 1000 cycles. \n\n// When the circuit isn't counting, the count[3:0] output is don't-care (whatever value is convenient for you to implement). At that point, the circuit must assert done to notify the user the timer has timed out, and waits until input ack is 1 before being reset to look for the next occurrence of the start sequence (1101).\n\n// The circuit should reset into a state where it begins searching for the input sequence 1101. The reset signal is active high synchronous. \n", "module_header": "module top_module(\n\tinput wire clk,\n\tinput wire reset,\n\tinput wire data,\n output wire [3:0] count,\n output reg counting,\n output reg done,\n input wire ack );\n", "original_code": "module top_module(\n\tinput wire clk,\n\tinput wire reset,\n\tinput wire data,\n output wire [3:0] count,\n output reg counting,\n output reg done,\n input wire ack );\n reg [3:0] delay;\n reg [3:0] remaining;\n reg [1:0] state;\n\n // States\n parameter [1:0] IDLE = 2'b00,\n START = 2'b01,\n WAIT = 2'b10;\n\n // Outputs\n wire [3:0] count_out;\n wire counting_out;\n\n // Instantiate the timer module\n timer t(.clk(clk), .reset(reset), .data(data), .delay(delay), .remaining(remaining), .state(state), .count(count_out), .counting(counting_out), .done(done));\n\n // State machine\n always @(posedge clk) begin\n if (reset) begin\n state <= IDLE;\n delay <= 0;\n remaining <= 0;\n counting <= 0;\n done <= 0;\n end\n else begin\n case (state)\n IDLE: begin\n if (data == 4'b1101) begin\n state <= START;\n end\n end\n START: begin\n delay <= {data, delay[3:1]};\n state <= WAIT;\n end\n WAIT: begin\n if (remaining == 0) begin\n counting <= 0;\n done <= 1;\n state <= IDLE;\n end\n else begin\n counting <= 1;\n remaining <= remaining - 1;\n end\n end\n endcase\n end\n end\n\n assign count = count_out;\n assign counting = counting_out;\n\n // Reset the timer when the input is acknowledged\n always @(posedge clk) begin\n if (ack) begin\n delay <= 0;\n remaining <= 0;\n counting <= 0;\n done <= 0;\n end\n end\n\nendmodule", "error": "23: error: Unknown module type: timer\n"} {"task_id": "review2015_fsm", "description": "We want to create a timer that:\n// (1) is started when a particular pattern (1101) is detected,\n// (2) shifts in 4 more bits to determine the duration to delay,\n// (3) waits for the counters to finish counting, and\n// (4) notifies the user and waits for the user to acknowledge the timer.\n// In this problem, implement just the finite-state machine that controls the timer. The data path (counters and some comparators) are not included here.\n// The serial data is available on the data input pin. When the pattern 1101 is received, the state machine must then assert output shift_ena for exactly 4 clock cycles. After that, the state machine asserts its counting output to indicate it is waiting for the counters, and waits until input done_counting is high.At that point, the state machine must assert done to notify the user the timer has timed out, and waits until input ack is 1 before being reset to look for the next occurrence of the start sequence (1101). The state machine should have a active high synchronous reset, setting the state to where it begins searching for the input sequence 1101.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n output reg shift_ena,\n output reg counting,\n input done_counting,\n output reg done,\n input ack );\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n output reg shift_ena,\n output reg counting,\n input done_counting,\n output reg done,\n input ack );\n parameter IDLE = 2'b00;\n parameter WAIT_DATA = 2'b01;\n parameter WAIT_COUNT = 2'b10;\n parameter WAIT_ACK = 2'b11;\n parameter [1:0] STATE = IDLE;\n\n always @(posedge clk) begin\n if (reset) begin\n STATE <= IDLE;\n shift_ena <= 1'b0;\n counting <= 1'b0;\n done <= 1'b0;\n end\n else begin\n case (STATE)\n IDLE: begin\n if (data == 1'b1) begin\n STATE <= WAIT_DATA;\n shift_ena <= 1'b1;\n end\n end\n WAIT_DATA: begin\n if (shift_ena == 1'b1) begin\n STATE <= WAIT_COUNT;\n shift_ena <= 1'b0;\n counting <= 1'b1;\n end\n end\n WAIT_COUNT: begin\n if (done_counting == 1'b1) begin\n STATE <= WAIT_ACK;\n counting <= 1'b0;\n done <= 1'b1;\n end\n end\n WAIT_ACK: begin\n if (ack == 1'b1) begin\n STATE <= IDLE;\n done <= 1'b0;\n end\n end\n endcase\n end\n end\n endmodule", "error": "33: error: Could not find variable ``STATE'' in ``top_module''\n40: error: Could not find variable ``STATE'' in ``top_module''\n47: error: Could not find variable ``STATE'' in ``top_module''\n27: error: Could not find variable ``STATE'' in ``top_module''\n18: error: Could not find variable ``STATE'' in ``top_module''\n"} {"task_id": "review2015_fsm", "description": "We want to create a timer that:\n// (1) is started when a particular pattern (1101) is detected,\n// (2) shifts in 4 more bits to determine the duration to delay,\n// (3) waits for the counters to finish counting, and\n// (4) notifies the user and waits for the user to acknowledge the timer.\n// In this problem, implement just the finite-state machine that controls the timer. The data path (counters and some comparators) are not included here.\n// The serial data is available on the data input pin. When the pattern 1101 is received, the state machine must then assert output shift_ena for exactly 4 clock cycles. After that, the state machine asserts its counting output to indicate it is waiting for the counters, and waits until input done_counting is high.At that point, the state machine must assert done to notify the user the timer has timed out, and waits until input ack is 1 before being reset to look for the next occurrence of the start sequence (1101). The state machine should have a active high synchronous reset, setting the state to where it begins searching for the input sequence 1101.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n output reg shift_ena,\n output reg counting,\n input done_counting,\n output reg done,\n input ack );\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n output reg shift_ena,\n output reg counting,\n input done_counting,\n output reg done,\n input ack );\n reg [1:0] state;\n reg [3:0] pattern;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= 2'b00;\n pattern <= 4'b0000;\n end else begin\n case (state)\n 2'b00: begin // searching for the start sequence 1101\n if (pattern == 4'b1101) begin\n shift_ena <= 1'b1;\n state <= 2'b01;\n end else begin\n pattern <= {pattern[2:0], data};\n end\n end\n 2'b01: begin // waiting for the shift enable signal\n if (shift_ena) begin\n state <= 2'b10;\n end\n end\n 2'b10: begin // waiting for the counters to finish counting\n if (done_counting) begin\n done <= 1'b1;\n state <= 2'b11;\n end\n end\n 2'b11: begin // waiting for the user to acknowledge the timer\n if (ack) begin\n state <= 2'b00;\n pattern <= 4'b0000;\n end\n end\n endcase\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n counting <= 1'b0;\n end else begin\n case (state)\n 2'b00: begin // searching for the start sequence 1101\n counting <= 1'b0;\n end\n 2'b01: begin // waiting for the shift enable signal\n counting <= 1'b1;\n end\n 2'b10: begin // waiting for the counters to finish counting\n counting <= 1'b1;\n end\n 2'b11: begin // waiting for the user to acknowledge the timer\n counting <= 1'b0;\n end\n endcase\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n shift_ena <= 1'b0;\n end else begin\n case (state)\n 2'b00: begin // searching for the start sequence 1101\n shift_ena <= 1'b0;\n end\n 2'b01: begin // waiting for the shift enable signal\n shift_ena <= 1'b1;\n end\n 2'b10: begin // waiting for the counters to finish counting\n shift_ena <= 1'b0;\n end\n 2'b11: begin // waiting for the user to acknowledge the timer\n shift_ena <= 1'b0;\n end\n endcase\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n done <= 1'b0;\n end else begin\n case (state)\n 2'b00: begin // searching for the start sequence 1101\n done <= 1'b0;\n end\n 2'b01: begin // waiting for the shift enable signal\n done <= 1'b0;\n end\n 2'b10: begin // waiting for the counters to finish counting\n done <= 1'b1;\n end\n 2'b11: begin // waiting for the user to acknowledge the timer\n done <= 1'b0;\n end\n endcase\n end\n end\n\n always @(posedge clk) begin\n if (reset) begin\n ack <= 1'b0;\n end else begin\n case (state)\n 2'b00: begin // searching for the start sequence 1101\n ack <= 1'b0;\n end\n 2'b01: begin // waiting for the shift enable signal\n ack <= 1'b0;\n end\n 2'b10: begin // waiting for the counters to finish counting\n ack <= 1'b0;\n end\n 2'b11: begin // waiting for the user to acknowledge the timer\n ack <= 1'b1;\n end\n endcase\n end\n end\n\n endmodule", "error": "113: error: 'ack' is not a valid l-value for a procedural assignment.\n9: : 'ack' is declared here as a wire.\n126: error: 'ack' is not a valid l-value for a procedural assignment.\n123: error: 'ack' is not a valid l-value for a procedural assignment.\n120: error: 'ack' is not a valid l-value for a procedural assignment.\n117: error: 'ack' is not a valid l-value for a procedural assignment.\n"} {"task_id": "review2015_fsmonehot", "description": "Given the following Moore state machine with 3 input (d, done_counting, ack) and 3 outputs (shift_ena, counting, done). Unless otherwise stated in the diagram below, assume outputs are 0 and inputs are don't cares.\n\n// S () --d=0--> S\n// S () --d=1--> S1\n// S1 () --d=0--> S\n// S1 () --d=1--> S11\n// S11 () --d=0--> S110\n// S11 () --d=1--> S11\n// S110 () --d=0--> S\n// S110 () --d=1--> B0\n// B0 (shift_ena=1) -- (always go to next cycle) --> B1\n// B1 (shift_ena=1) -- (always go to next cycle) --> B2\n// B2 (shift_ena=1) -- (always go to next cycle) --> B3\n// B3 (shift_ena=1) -- (always go to next cycle) --> Count\n// Count (counting=1) --!(done_counting)--> Count\n// Count (counting=1) --(done_counting)--> Wait\n// Wait (done=1) --ack=0--> Wait\n// Wait (done=1) --ack=1--> S\n\n// At reset, the state machine starts in state \"S\". Derive next-state logic equations and output logic equations by inspection assuming the following one-hot encoding is used: (S, S1, S11, S110, B0, B1, B2, B3, Count, Wait) = (10'b0000000001, 10'b0000000010, 10'b0000000100, ... , 10'b1000000000)\n\n// Derive state transition and output logic equations by inspection assuming a one-hot encoding. Implement only the state transition logic and output logic (the combinational logic portion) for this state machine.\n\n// Write code that generates the following equations:\n\n// - B3_next -- next-state logic for state B3\n// - S_next\n// - S1_next\n// - Count_next\n// - Wait_next\n// - done -- output logic\n// - counting\n// - shift_ena\n", "module_header": "module top_module(\n input d,\n input done_counting,\n input ack,\n input [9:0] state, // 10-bit one-hot current state\n output B3_next,\n output S_next,\n output S1_next,\n output Count_next,\n output Wait_next,\n output done,\n output counting,\n output shift_ena\n );\n", "original_code": "module top_module(\n input d,\n input done_counting,\n input ack,\n input [9:0] state, // 10-bit one-hot current state\n output B3_next,\n output S_next,\n output S1_next,\n output Count_next,\n output Wait_next,\n output done,\n output counting,\n output shift_ena\n );\n // State transition logic\n wire [9:0] S_next_wire = (state[0] & ~d) ? 10'b0000000001 : 10'b0000000000;\n wire [9:0] S1_next_wire = (state[1] & d) ? 10'b0000000010 : 10'b0000000000;\n wire [9:0] S11_next_wire = (state[2] & d) ? 10'b0000000100 : 10'b0000000000;\n wire [9:0] S110_next_wire = (state[3] & ~d) ? 10'b0000001000 : 10'b0000000000;\n wire [9:0] B0_next_wire = (state[4]) ? 10'b0000010000 : 10'b0000000000;\n wire [9:0] B1_next_wire = (state[5]) ? 10'b0000100000 : 10'b0000000000;\n wire [9:0] B2_next_wire = (state[6]) ? 10'b0001000000 : 10'b0000000000;\n wire [9:0] B3_next_wire = (state[7]) ? 10'b0010000000 : 10'b0000000000;\n wire [9:0] Count_next_wire = (state[8] & ~done_counting) ? 10'b0100000000 : 10'b0000000000;\n wire [9:0] Wait_next_wire = (state[9] & ~ack) ? 10'b1000000000 : 10'b0000000000;\n\n // Output assignment logic\n assign shift_ena = (B0_next_wire | B1_next_wire | B2_next_wire | B3_next_wire);\n assign counting = (Count_next_wire);\n assign done = (Wait_next_wire);\n\n // Triggering conditions for always blocks\n always @(posedge clk) begin\n B3_next <= B3_next_wire;\n S_next <= S_next_wire;\n S1_next <= S1_next_wire;\n Count_next <= Count_next_wire;\n Wait_next <= Wait_next_wire;\n end\n\n endmodule", "error": "35: error: 'S_next' is not a valid l-value for a procedural assignment.\n38: error: 'Wait_next' is not a valid l-value for a procedural assignment.\n8: : 'S1_next' is declared here as a wire.\n6: : 'B3_next' is declared here as a wire.\n7: : 'S_next' is declared here as a wire.\n34: error: 'B3_next' is not a valid l-value for a procedural assignment.\n33: error: Failed to evaluate event expression 'posedge clk'.\n36: error: 'S1_next' is not a valid l-value for a procedural assignment.\n33: error: Unable to bind wire/reg/memory `clk' in `top_module'\n37: error: 'Count_next' is not a valid l-value for a procedural assignment.\n10: : 'Wait_next' is declared here as a wire.\n9: : 'Count_next' is declared here as a wire.\n"} {"task_id": "review2015_fsmonehot", "description": "Given the following Moore state machine with 3 input (d, done_counting, ack) and 3 outputs (shift_ena, counting, done). Unless otherwise stated in the diagram below, assume outputs are 0 and inputs are don't cares.\n\n// S () --d=0--> S\n// S () --d=1--> S1\n// S1 () --d=0--> S\n// S1 () --d=1--> S11\n// S11 () --d=0--> S110\n// S11 () --d=1--> S11\n// S110 () --d=0--> S\n// S110 () --d=1--> B0\n// B0 (shift_ena=1) -- (always go to next cycle) --> B1\n// B1 (shift_ena=1) -- (always go to next cycle) --> B2\n// B2 (shift_ena=1) -- (always go to next cycle) --> B3\n// B3 (shift_ena=1) -- (always go to next cycle) --> Count\n// Count (counting=1) --!(done_counting)--> Count\n// Count (counting=1) --(done_counting)--> Wait\n// Wait (done=1) --ack=0--> Wait\n// Wait (done=1) --ack=1--> S\n\n// At reset, the state machine starts in state \"S\". Derive next-state logic equations and output logic equations by inspection assuming the following one-hot encoding is used: (S, S1, S11, S110, B0, B1, B2, B3, Count, Wait) = (10'b0000000001, 10'b0000000010, 10'b0000000100, ... , 10'b1000000000)\n\n// Derive state transition and output logic equations by inspection assuming a one-hot encoding. Implement only the state transition logic and output logic (the combinational logic portion) for this state machine.\n\n// Write code that generates the following equations:\n\n// - B3_next -- next-state logic for state B3\n// - S_next\n// - S1_next\n// - Count_next\n// - Wait_next\n// - done -- output logic\n// - counting\n// - shift_ena\n", "module_header": "module top_module(\n input d,\n input done_counting,\n input ack,\n input [9:0] state, // 10-bit one-hot current state\n output B3_next,\n output S_next,\n output S1_next,\n output Count_next,\n output Wait_next,\n output done,\n output counting,\n output shift_ena\n );\n", "original_code": "module top_module(\n input d,\n input done_counting,\n input ack,\n input [9:0] state, // 10-bit one-hot current state\n output B3_next,\n output S_next,\n output S1_next,\n output Count_next,\n output Wait_next,\n output done,\n output counting,\n output shift_ena\n );\n parameter S = 10'b0000000001, S1 = 10'b0000000010, S11 = 10'b0000000100, S110 = 10'b0000001000, B0 = 10'b0000010000, B1 = 10'b0000100000, B2 = 10'b0001000000, B3 = 10'b0010000000, Count = 10'b0100000000, Wait = 10'b1000000000;\n \n assign S_next = (state == S) && ~d;\n assign S1_next = (state == S1) && ~d;\n assign S11_next = (state == S11) && ~d;\n assign S110_next = (state == S110) && ~d;\n assign B0_next = (state == B0);\n assign B1_next = (state == B1);\n assign B2_next = (state == B2);\n assign B3_next = (state == B3);\n assign Count_next = (state == Count) && ~done_counting;\n assign Wait_next = (state == Wait) && ack;\n \n assign done = (state == Wait);\n assign counting = (state == Count);\n assign shift_ena = (state == B3 || state == B2 || state == B1 || state == B0);\n\nendmodule", "error": "22: warning: implicit definition of wire 'B1_next'.\n23: warning: implicit definition of wire 'B2_next'.\n19: warning: implicit definition of wire 'S11_next'.\n20: warning: implicit definition of wire 'S110_next'.\n21: warning: implicit definition of wire 'B0_next'.\n"} {"task_id": "review2015_fsmseq", "description": "Build a finite-state machine that searches for the sequence 1101 in an input bit stream. When the sequence is found, it should set start_shifting to 1, forever, until reset. Reset is active high synchronous.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n\toutput start_shifting);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n\toutput start_shifting);\n parameter IDLE = 2'b00, SEQ1 = 2'b01, SEQ2 = 2'b10, SEQ3 = 2'b11;\n\n reg [1:0] state, next_state;\n\n always @(posedge clk, posedge reset)\n if(reset)\n state <= IDLE;\n else\n state <= next_state;\n\n always @* begin\n next_state = IDLE;\n start_shifting = 0;\n case(state)\n IDLE: begin\n if(data == 1)\n next_state = SEQ1;\n else if(data == 0)\n next_state = IDLE;\n end\n SEQ1: begin\n if(data == 1)\n next_state = SEQ2;\n else if(data == 0)\n next_state = IDLE;\n end\n SEQ2: begin\n if(data == 0)\n next_state = SEQ3;\n else if(data == 1)\n next_state = SEQ1;\n end\n SEQ3: begin\n if(data == 1)\n next_state = SEQ1;\n else if(data == 0)\n next_state = IDLE;\n start_shifting = 1;\n end\n endcase\n end\n endmodule", "error": "43: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n18: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n5: : 'start_shifting' is declared here as a wire.\n"} {"task_id": "review2015_fsmseq", "description": "Build a finite-state machine that searches for the sequence 1101 in an input bit stream. When the sequence is found, it should set start_shifting to 1, forever, until reset. Reset is active high synchronous.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n\toutput start_shifting);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\tinput data,\n\toutput start_shifting);\n parameter IDLE = 2'b00,\n SEQ1 = 2'b01,\n SEQ2 = 2'b10,\n SEQ3 = 2'b11,\n SEQ4 = 2'b11;\n\n reg [1:0] state, next_state;\n\n always @(posedge clk) begin\n if(reset) begin\n state <= IDLE;\n start_shifting <= 0;\n end\n else begin\n state <= next_state;\n end\n end\n\n always @(*) begin\n case(state)\n IDLE: begin\n if(data) begin\n next_state = SEQ1;\n start_shifting = 0;\n end\n else begin\n next_state = IDLE;\n start_shifting = 0;\n end\n end\n SEQ1: begin\n if(data) begin\n next_state = SEQ2;\n start_shifting = 0;\n end\n else begin\n next_state = IDLE;\n start_shifting = 0;\n end\n end\n SEQ2: begin\n if(data) begin\n next_state = SEQ3;\n start_shifting = 0;\n end\n else begin\n next_state = IDLE;\n start_shifting = 0;\n end\n end\n SEQ3: begin\n if(data) begin\n next_state = SEQ4;\n start_shifting = 1;\n end\n else begin\n next_state = IDLE;\n start_shifting = 0;\n end\n end\n SEQ4: begin\n if(data) begin\n next_state = IDLE;\n start_shifting = 0;\n end\n else begin\n next_state = IDLE;\n start_shifting = 0;\n end\n end\n endcase\n end\n\nendmodule", "error": "29: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n43: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n59: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n63: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n69: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n39: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n33: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n73: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n5: : 'start_shifting' is declared here as a wire.\n53: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n49: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n17: error: 'start_shifting' is not a valid l-value for a procedural assignment.\n"} {"task_id": "review2015_fsmshift", "description": "This module is a part of the FSM for controlling the shift register, we want the ability to enable the shift register for exactly 4 clock cycles whenever the proper bit pattern is detected. Whenever the FSM is reset, assert shift_ena for 4 cycles, then 0 forever (until reset). Reset should be active high synchronous.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput shift_ena);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput shift_ena);\n parameter SHIFT_ENA_CYCLES = 4;\n\n reg [31:0] shift_ena_counter;\n\n always @(posedge clk) begin\n if (reset) begin\n shift_ena_counter <= 0;\n shift_ena <= 1'b1;\n end else begin\n if (shift_ena_counter < SHIFT_ENA_CYCLES) begin\n shift_ena_counter <= shift_ena_counter + 1;\n shift_ena <= 1'b1;\n end else begin\n shift_ena <= 1'b0;\n end\n end\n end\n endmodule", "error": "18: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n16: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n4: : 'shift_ena' is declared here as a wire.\n12: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n"} {"task_id": "review2015_fsmshift", "description": "This module is a part of the FSM for controlling the shift register, we want the ability to enable the shift register for exactly 4 clock cycles whenever the proper bit pattern is detected. Whenever the FSM is reset, assert shift_ena for 4 cycles, then 0 forever (until reset). Reset should be active high synchronous.", "module_header": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput shift_ena);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput reset,\n\toutput shift_ena);\n reg [1:0] state;\n parameter SHIFT = 2'b00, WAIT = 2'b01;\n parameter SHIFT_ENA = 4'b1111;\n\n always @(posedge clk) begin\n if (reset) begin\n state <= SHIFT;\n shift_ena <= 1'b1;\n end else begin\n case (state)\n SHIFT: begin\n shift_ena <= SHIFT_ENA;\n state <= WAIT;\n end\n WAIT: begin\n shift_ena <= 1'b0;\n if (reset) begin\n state <= SHIFT;\n end\n end\n endcase\n end\n end\n\nendmodule", "error": "20: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n16: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n4: : 'shift_ena' is declared here as a wire.\n12: error: 'shift_ena' is not a valid l-value for a procedural assignment.\n"} {"task_id": "ringer", "description": "Suppose you are designing a circuit to control a cellphone's ringer and vibration motor. Whenever the phone needs to ring from an incoming call (input ring), your circuit must either turn on the ringer (output ringer = 1) or the motor (output motor = 1), but not both. If the phone is in vibrate mode (input vibrate_mode = 1), turn on the motor. Otherwise, turn on the ringer.", "module_header": "module top_module(\n\tinput ring, \n\tinput vibrate_mode,\n\toutput ringer,\n\toutput motor\n);\n", "original_code": "module top_module(\n\tinput ring, \n\tinput vibrate_mode,\n\toutput ringer,\n\toutput motor\n);\n assign ringer = (ring && !vibrate_mode) ? 1'b1 : 0'b0;\n assign motor = (ring && vibrate_mode) ? 1'b1 : 0'b0;\n\nendmodule", "error": "8: error: Sized numeric constant must have a size greater than zero.\n7: error: Sized numeric constant must have a size greater than zero.\n"} {"task_id": "ringer", "description": "Suppose you are designing a circuit to control a cellphone's ringer and vibration motor. Whenever the phone needs to ring from an incoming call (input ring), your circuit must either turn on the ringer (output ringer = 1) or the motor (output motor = 1), but not both. If the phone is in vibrate mode (input vibrate_mode = 1), turn on the motor. Otherwise, turn on the ringer.", "module_header": "module top_module(\n\tinput ring, \n\tinput vibrate_mode,\n\toutput ringer,\n\toutput motor\n);\n", "original_code": "module top_module(\n\tinput ring, \n\tinput vibrate_mode,\n\toutput ringer,\n\toutput motor\n);\n reg ringer;\n reg motor;\n\n always @(posedge ring) begin\n if (ring == 1'b1) begin\n if (vibrate_mode == 1'b0) begin\n ringer <= 1'b1;\n motor <= 1'b0;\n end else begin\n ringer <= 1'b0;\n motor <= 1'b1;\n end\n end else begin\n ringer <= 1'b0;\n motor <= 1'b0;\n end\n end\n\nendmodule", "error": "4: : It was declared here as a net.\n8: error: 'motor' has already been declared in this scope.\n7: error: 'ringer' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "rotate100", "description": "Build a 100-bit left/right rotator, with synchronous load and left/right enable. A rotator shifts-in the shifted-out bit from the other end of the register, unlike a shifter that discards the shifted-out bit and shifts in a zero. If enabled, a rotator rotates the bits around and does not modify/discard them. \n// (1) load: Loads shift register with data[99:0] instead of rotating. Synchronous active high.\n// (2) ena[1:0]: Synchronous. Chooses whether and which direction to rotate: \n// (a) 2'b01 rotates right by one bit, \n// (b) 2'b10 rotates left by one bit, \n// (c) 2'b00 and 2'b11 do not rotate. \n// (3) q: The contents of the rotator.", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [1:0] ena,\n\tinput [99:0] data,\n\toutput reg [99:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [1:0] ena,\n\tinput [99:0] data,\n\toutput reg [99:0] q);\n reg [99:0] reg_q;\n reg [1:0] reg_ena;\n\n always @(posedge clk) begin\n if (load) begin\n reg_q <= data;\n end else begin\n case (ena)\n 2'b01: reg_q <= {reg_q[98:0], reg_q[99]};\n 2'b10: reg_q <= {reg_q[1:99], reg_q[0]};\n default: reg_q <= reg_q;\n endcase\n end\n end\n\n assign q = reg_q;\n\n endmodule", "error": "16: error: part select reg_q[1:99] is out of order.\n"} {"task_id": "rotate100", "description": "Build a 100-bit left/right rotator, with synchronous load and left/right enable. A rotator shifts-in the shifted-out bit from the other end of the register, unlike a shifter that discards the shifted-out bit and shifts in a zero. If enabled, a rotator rotates the bits around and does not modify/discard them. \n// (1) load: Loads shift register with data[99:0] instead of rotating. Synchronous active high.\n// (2) ena[1:0]: Synchronous. Chooses whether and which direction to rotate: \n// (a) 2'b01 rotates right by one bit, \n// (b) 2'b10 rotates left by one bit, \n// (c) 2'b00 and 2'b11 do not rotate. \n// (3) q: The contents of the rotator.", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [1:0] ena,\n\tinput [99:0] data,\n\toutput reg [99:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [1:0] ena,\n\tinput [99:0] data,\n\toutput reg [99:0] q);\n reg [99:0] reg_q;\n always @(posedge clk) begin\n if (load) begin\n reg_q <= data; // load data\n end\n else begin\n case (ena)\n 2'b01: begin\n reg_q[0] <= reg_q[99]; // rotate right by one bit\n reg_q[99:1] <= reg_q[98:0];\n end\n 2'b10: begin\n reg_q[99] <= reg_q[0]; // rotate left by one bit\n reg_q[0:98] <= reg_q[1:99];\n end\n endcase\n end\n end\n assign q = reg_q;\n\nendmodule", "error": "20: error: part select reg_q[0:98] is reversed.\n20: error: part select reg_q[1:99] is out of order.\n"} {"task_id": "rule110", "description": "Rule 110 is a one-dimensional cellular automaton with interesting properties (such as being Turing-complete). There is a one-dimensional array of cells (on or off). At each time step, the state of each cell changes. In Rule 110, the next state of each cell depends only on itself and its two neighbours, according to the following table:\n// Left | Center | Right | Center's next state\n// 1 | 1 | 1 | 0\n// 1 | 1 | 0 | 1\n// 1 | 0 | 1 | 1\n// 1 | 0 | 0 | 0\n// 0 | 1 | 1 | 1\n// 0 | 1 | 0 | 1\n// 0 | 0 | 1 | 1\n// 0 | 0 | 0 | 0 \n// In this circuit, create a 512-cell system (q[511:0]), and advance by one time step each clock cycle. The synchronous active high load input indicates the state of the system should be loaded with data[511:0]. Assume the boundaries (q[-1] and q[512]) are both zero (off).", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n // Define the rule as a function\n always @(*) begin\n q = {q[510:0], ((q[511:510] & q[509:508]) | (~q[511:510] & ~q[509:508])) & (q[509:508] ^ q[511:510])};\n end\n\n // Load new data into q on a rising edge of load\n always @(posedge clk) begin\n if (load) begin\n q <= data;\n end\n end\n\n // Boundaries are always 0\n assign q[-1] = 0;\n assign q[512] = 0;\n\nendmodule", "error": "14: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n19: sorry: part selects straddling the start of signal (q[-('sd1)]) are not currently supported.\n20: error: Index q[512] is out of range.\n8: error: Cannot perform procedural assignment to variable 'q' because it is also continuously assigned.\n"} {"task_id": "rule110", "description": "Rule 110 is a one-dimensional cellular automaton with interesting properties (such as being Turing-complete). There is a one-dimensional array of cells (on or off). At each time step, the state of each cell changes. In Rule 110, the next state of each cell depends only on itself and its two neighbours, according to the following table:\n// Left | Center | Right | Center's next state\n// 1 | 1 | 1 | 0\n// 1 | 1 | 0 | 1\n// 1 | 0 | 1 | 1\n// 1 | 0 | 0 | 0\n// 0 | 1 | 1 | 1\n// 0 | 1 | 0 | 1\n// 0 | 0 | 1 | 1\n// 0 | 0 | 0 | 0 \n// In this circuit, create a 512-cell system (q[511:0]), and advance by one time step each clock cycle. The synchronous active high load input indicates the state of the system should be loaded with data[511:0]. Assume the boundaries (q[-1] and q[512]) are both zero (off).", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n\n always @(posedge clk) begin\n // always block triggered on positive edge of clock signal.\n if (load) begin\n // If load signal is high.\n q <= data; // Assign data to q.\n end else begin\n // If load signal is low.\n q[0] <= (q[1] & q[2]) | (~q[1] & ~q[2]); // Calculate new value for q[0].\n q[511] <= (q[510] & q[511]) | (~q[510] & ~q[511]); // Calculate new value for q[511].\n for (i = 1; i < 511; i = i + 1) begin\n // Loop through q from index 1 to 510.\n q[i] <= (q[i-1] & q[i+1]) | (~q[i-1] & ~q[i+1]); // Calculate new value for each q[i].\n end\n end\n end\n // end of always block\n endmodule", "error": "16: register ``i'' unknown in top_module.\n"} {"task_id": "rule90", "description": "Rule 90 is a one-dimensional cellular automaton with interesting properties. The rules are simple. There is a one-dimensional array of cells (on or off). At each time step, the next state of each cell is the XOR of the cell's two current neighbours:\n// Left | Center | Right | Center's next state\n// 1 | 1 | 1 | 0\n// 1 | 1 | 0 | 1\n// 1 | 0 | 1 | 0\n// 1 | 0 | 0 | 1\n// 0 | 1 | 1 | 1\n// 0 | 1 | 0 | 0 \n// 0 | 0 | 1 | 1\n// 0 | 0 | 0 | 0\n// In this circuit, create a 512-cell system (q[511:0]), and advance by one time step each clock cycle. The load input indicates the state of the system should be loaded with data[511:0]. Assume the boundaries (q[-1] and q[512]) are both zero (off).", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n // intermediate storage\n reg [513:0] current_state, next_state;\n reg [2:0] left, center, right;\n\n // load initial state\n always @(posedge clk) begin\n if (load) begin\n current_state <= {1'b0, data, 1'b0};\n end else begin\n current_state <= next_state;\n end\n end\n\n // calculate next state\n always @(*) begin\n next_state = {1'b0, current_state[511:1], 1'b0};\n for (i = 0; i < 512; i = i + 1) begin\n left = current_state[i-1:i-2];\n center = current_state[i:i+1];\n right = current_state[i+2:i+3];\n next_state[i+1] = (left ^ center ^ right);\n end\n end\n\n // output current state\n always @(posedge clk) begin\n q <= current_state[511:0];\n end\n\n endmodule", "error": "22: register ``i'' unknown in top_module.\n"} {"task_id": "rule90", "description": "Rule 90 is a one-dimensional cellular automaton with interesting properties. The rules are simple. There is a one-dimensional array of cells (on or off). At each time step, the next state of each cell is the XOR of the cell's two current neighbours:\n// Left | Center | Right | Center's next state\n// 1 | 1 | 1 | 0\n// 1 | 1 | 0 | 1\n// 1 | 0 | 1 | 0\n// 1 | 0 | 0 | 1\n// 0 | 1 | 1 | 1\n// 0 | 1 | 0 | 0 \n// 0 | 0 | 1 | 1\n// 0 | 0 | 0 | 0\n// In this circuit, create a 512-cell system (q[511:0]), and advance by one time step each clock cycle. The load input indicates the state of the system should be loaded with data[511:0]. Assume the boundaries (q[-1] and q[512]) are both zero (off).", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput [511:0] data,\n\toutput reg [511:0] q);\n always @(posedge clk) begin\n if (load) begin\n q <= data;\n end else begin\n q[0] <= q[1] ^ q[511];\n q[511] <= q[510] ^ q[0];\n for (i = 1; i < 511; i = i + 1) begin\n q[i] <= q[i-1] ^ q[i+1];\n end\n end\n end\n\n endmodule", "error": "12: register ``i'' unknown in top_module.\n"} {"task_id": "shift18", "description": "Build a 64-bit arithmetic shift register, with synchronous load. The shifter can shift both left and right, and by 1 or 8 bit positions, selected by \"amount.\" Assume the right shit is an arithmetic right shift. \n\n// Signals are defined as below:\n// (1) load: Loads shift register with data[63:0] instead of shifting. Active high.\n// (2) ena: Chooses whether to shift. Active high. \n// (3) amount: Chooses which direction and how much to shift. \n// (a) 2'b00: shift left by 1 bit. \n// (b) 2'b01: shift left by 8 bits. \n// (c) 2'b10: shift right by 1 bit. \n// (d) 2'b11: shift right by 8 bits. \n// (4) q: The contents of the shifter.", "module_header": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput ena,\n\tinput [1:0] amount,\n\tinput [63:0] data,\n\toutput reg [63:0] q);\n", "original_code": "module top_module(\n\tinput clk,\n\tinput load,\n\tinput ena,\n\tinput [1:0] amount,\n\tinput [63:0] data,\n\toutput reg [63:0] q);\n reg [63:0] shift_reg;\n \n always @(posedge clk) begin\n if (load) begin\n shift_reg <= data;\n end else if (ena) begin\n case (amount)\n 2'b00: shift_reg <= {shift_reg[62:0], 1'b0};\n 2'b01: shift_reg <= {shift_reg[47:0], 1'b0};\n 2'b10: shift_reg <= {1'b1, shift_reg[63:1]};\n 2'b11: shift_reg <= {8'b11111111, shift_reg[7:8]};\n endcase\n end\n end\n \n assign q = shift_reg;\n \nendmodule", "error": "18: error: part select shift_reg[7:8] is out of order.\n"} {"task_id": "step_one", "description": "Build a circuit with no inputs and one output. That output should always drive 1 (or logic high).", "module_header": "module top_module(\n\toutput one);\n", "original_code": "module top_module(\n\toutput one);\n // Module is supply voltage agnostic, over-voltage and under-voltage safe\n supply1 VPWR;\n supply0 VGND;\n supply1 VPB ;\n supply0 VNB ;\n\n always @(*) begin\n one = 1'b1;\n end\n endmodule", "error": "10: error: 'one' is not a valid l-value for a procedural assignment.\n2: : 'one' is declared here as a wire.\n"} {"task_id": "step_one", "description": "Build a circuit with no inputs and one output. That output should always drive 1 (or logic high).", "module_header": "module top_module(\n\toutput one);\n", "original_code": "module top_module(\n\toutput one);\n reg one;\n\n always @(posedge clk)\n begin\n one <= 1'b1;\n end\n\n endmodule", "error": "3: error: 'one' has already been declared in this scope.\n2: : It was declared here as a net.\n"} {"task_id": "thermostat", "description": "A heating/cooling thermostat controls both a heater (during winter) and an air conditioner (during summer). Implement a circuit that will turn on and off the heater, air conditioning, and blower fan as appropriate. The thermostat can be in one of two modes: heating (mode = 1) and cooling (mode = 0). In heating mode, turn the heater on when it is too cold (too_cold = 1) but do not use the air conditioner. In cooling mode, turn the air conditioner on when it is too hot (too_hot = 1), but do not turn on the heater. When the heater or air conditioner are on, also turn on the fan to circulate the air. In addition, the user can also request the fan to turn on (fan_on = 1), even if the heater and air conditioner are off.", "module_header": "module top_module(\n\tinput mode,\n\tinput too_cold, \n\tinput too_hot,\n\tinput fan_on,\n\toutput heater,\n\toutput aircon,\n\toutput fan\n);\n", "original_code": "module top_module(\n\tinput mode,\n\tinput too_cold, \n\tinput too_hot,\n\tinput fan_on,\n\toutput heater,\n\toutput aircon,\n\toutput fan\n);\n parameter mode = 1;\n parameter too_cold = 1;\n parameter too_hot = 0;\n parameter fan_on = 0;\n\n reg heater_reg;\n reg aircon_reg;\n reg fan_reg;\n\n always @(posedge clk) begin\n if (mode == 1 && too_cold == 1) begin\n heater_reg <= 1;\n fan_reg <= 1;\n end else if (mode == 0 && too_hot == 1) begin\n aircon_reg <= 1;\n fan_reg <= 1;\n end else if (fan_on == 1) begin\n fan_reg <= 1;\n end else begin\n heater_reg <= 0;\n aircon_reg <= 0;\n fan_reg <= 0;\n end\n end\n\n assign heater = heater_reg;\n assign aircon = aircon_reg;\n assign fan = fan_reg;\n\n endmodule", "error": "11: error: 'too_cold' has already been declared in this scope.\n4: : It was declared here as a net.\n2: : It was declared here as a net.\n10: error: 'mode' has already been declared in this scope.\n13: error: 'fan_on' has already been declared in this scope.\n5: : It was declared here as a net.\n12: error: 'too_hot' has already been declared in this scope.\n3: : It was declared here as a net.\n"} {"task_id": "thermostat", "description": "A heating/cooling thermostat controls both a heater (during winter) and an air conditioner (during summer). Implement a circuit that will turn on and off the heater, air conditioning, and blower fan as appropriate. The thermostat can be in one of two modes: heating (mode = 1) and cooling (mode = 0). In heating mode, turn the heater on when it is too cold (too_cold = 1) but do not use the air conditioner. In cooling mode, turn the air conditioner on when it is too hot (too_hot = 1), but do not turn on the heater. When the heater or air conditioner are on, also turn on the fan to circulate the air. In addition, the user can also request the fan to turn on (fan_on = 1), even if the heater and air conditioner are off.", "module_header": "module top_module(\n\tinput mode,\n\tinput too_cold, \n\tinput too_hot,\n\tinput fan_on,\n\toutput heater,\n\toutput aircon,\n\toutput fan\n);\n", "original_code": "module top_module(\n\tinput mode,\n\tinput too_cold, \n\tinput too_hot,\n\tinput fan_on,\n\toutput heater,\n\toutput aircon,\n\toutput fan\n);\n reg heater;\n reg aircon;\n reg fan;\n\n always @(posedge clk) begin\n if (mode == 1'b1) begin // cooling mode\n if (too_hot == 1'b1) begin\n heater <= 1'b0;\n aircon <= 1'b1;\n end else begin\n heater <= 1'b0;\n aircon <= 1'b0;\n end\n end else begin // heating mode\n if (too_cold == 1'b1) begin\n heater <= 1'b1;\n aircon <= 1'b0;\n end else begin\n heater <= 1'b0;\n aircon <= 1'b0;\n end\n end\n if (fan_on == 1'b1 || heater == 1'b1 || aircon == 1'b1) begin\n fan <= 1'b1;\n end else begin\n fan <= 1'b0;\n end\n end\n\nendmodule", "error": "11: error: 'aircon' has already been declared in this scope.\n10: error: 'heater' has already been declared in this scope.\n8: : It was declared here as a net.\n12: error: 'fan' has already been declared in this scope.\n7: : It was declared here as a net.\n6: : It was declared here as a net.\n"} {"task_id": "timer", "description": "Implement a timer that counts down for a given number of clock cycles, then asserts a signal to indicate that the given duration has elapsed. A good way to implement this is with a down-counter that asserts an output signal when the count becomes 0. At each clock cycle: \n// (1) If load = 1, load the internal counter with the 10-bit data, the number of clock cycles the timer should count before timing out. The counter can be loaded at any time, including when it is still counting and has not yet reached 0. \n// (2) If load = 0, the internal counter should decrement by 1. The output signal tc (\"terminal count\") indicates whether the internal counter has reached 0. Once the internal counter has reached 0, it should stay 0 (stop counting) until the counter is loaded again.\n\n", "module_header": "module top_module(\n\tinput clk, \n\tinput load, \n\tinput [9:0] data, \n\toutput tc\n);\n", "original_code": "module top_module(\n\tinput clk, \n\tinput load, \n\tinput [9:0] data, \n\toutput tc\n);\n // Your code here\n reg [9:0] count;\n reg tc_reg;\n always @(posedge clk) begin\n if (load) begin\n count <= data;\n tc_reg <= 0;\n end else if (count > 0) begin\n count <= count - 1;\n tc_reg <= 0;\n end else begin\n tc_reg <= 1;\n end\n end\n assign tc = tc_reg;\n assign tc_reg = (count == 0) ? 1'b1 : 1'b0;\nendmodule", "error": "13: error: Cannot perform procedural assignment to variable 'tc_reg' because it is also continuously assigned.\n18: error: Cannot perform procedural assignment to variable 'tc_reg' because it is also continuously assigned.\n16: error: Cannot perform procedural assignment to variable 'tc_reg' because it is also continuously assigned.\n"} {"task_id": "timer", "description": "Implement a timer that counts down for a given number of clock cycles, then asserts a signal to indicate that the given duration has elapsed. A good way to implement this is with a down-counter that asserts an output signal when the count becomes 0. At each clock cycle: \n// (1) If load = 1, load the internal counter with the 10-bit data, the number of clock cycles the timer should count before timing out. The counter can be loaded at any time, including when it is still counting and has not yet reached 0. \n// (2) If load = 0, the internal counter should decrement by 1. The output signal tc (\"terminal count\") indicates whether the internal counter has reached 0. Once the internal counter has reached 0, it should stay 0 (stop counting) until the counter is loaded again.\n\n", "module_header": "module top_module(\n\tinput clk, \n\tinput load, \n\tinput [9:0] data, \n\toutput tc\n);\n", "original_code": "module top_module(\n\tinput clk, \n\tinput load, \n\tinput [9:0] data, \n\toutput tc\n);\n reg [9:0] count;\n\n always @(posedge clk) begin\n if (load) begin\n count <= data;\n end else begin\n count <= count - 1;\n end\n if (count == 0) begin\n tc <= 1;\n end else begin\n tc <= 0;\n end\n end\n\nendmodule", "error": "16: error: 'tc' is not a valid l-value for a procedural assignment.\n5: : 'tc' is declared here as a wire.\n18: error: 'tc' is not a valid l-value for a procedural assignment.\n"} {"task_id": "truthtable1", "description": "Create a combinational circuit that implements the truth table.\n\n// x3 | x2 | x1 | f\n// 0 | 0 | 0 | 0\n// 0 | 0 | 1 | 0\n// 0 | 1 | 0 | 1\n// 0 | 1 | 1 | 1\n// 1 | 0 | 0 | 0\n// 1 | 0 | 1 | 1\n// 1 | 1 | 0 | 0\n// 1 | 1 | 1 | 1", "module_header": "module top_module (\n\tinput x3,\n\tinput x2,\n\tinput x1,\n\toutput f\n);\n", "original_code": "module top_module (\n\tinput x3,\n\tinput x2,\n\tinput x1,\n\toutput f\n);\n parameter SIZE = 8;\n reg [SIZE-1:0] f;\n\n always @* begin\n if (x3 && x2 && x1)\n f = 8'b11111111;\n else if (x3 && x2)\n f = 8'b11111110;\n else if (x3 && x1)\n f = 8'b11111100;\n else if (x2 && x1)\n f = 8'b11111000;\n else if (x3)\n f = 8'b11110000;\n else if (x2)\n f = 8'b11100000;\n else if (x1)\n f = 8'b11000000;\n else\n f = 8'b00000000;\n end\n\nendmodule", "error": "8: error: 'f' has already been declared in this scope.\n5: : It was declared here as a net.\n"} {"task_id": "truthtable1", "description": "Create a combinational circuit that implements the truth table.\n\n// x3 | x2 | x1 | f\n// 0 | 0 | 0 | 0\n// 0 | 0 | 1 | 0\n// 0 | 1 | 0 | 1\n// 0 | 1 | 1 | 1\n// 1 | 0 | 0 | 0\n// 1 | 0 | 1 | 1\n// 1 | 1 | 0 | 0\n// 1 | 1 | 1 | 1", "module_header": "module top_module (\n\tinput x3,\n\tinput x2,\n\tinput x1,\n\toutput f\n);\n", "original_code": "module top_module (\n\tinput x3,\n\tinput x2,\n\tinput x1,\n\toutput f\n);\n parameter [0:1] x3_values = 2'b00;\n parameter [0:1] x2_values = 2'b00;\n parameter [0:1] x1_values = 2'b00;\n parameter [0:1] f_values = 2'b00;\n\n always @(*) begin\n if (x3 == x3_values[0] && x2 == x2_values[0] && x1 == x1_values[0])\n f = f_values[0];\n else if (x3 == x3_values[0] && x2 == x2_values[0] && x1 == x1_values[1])\n f = f_values[1];\n else if (x3 == x3_values[0] && x2 == x2_values[1] && x1 == x1_values[0])\n f = f_values[2];\n else if (x3 == x3_values[0] && x2 == x2_values[1] && x1 == x1_values[1])\n f = f_values[3];\n else if (x3 == x3_values[1] && x2 == x2_values[0] && x1 == x1_values[0])\n f = f_values[4];\n else if (x3 == x3_values[1] && x2 == x2_values[0] && x1 == x1_values[1])\n f = f_values[5];\n else if (x3 == x3_values[1] && x2 == x2_values[1] && x1 == x1_values[0])\n f = f_values[6];\n else if (x3 == x3_values[1] && x2 == x2_values[1] && x1 == x1_values[1])\n f = f_values[7];\n end\n\nendmodule", "error": "22: error: 'f' is not a valid l-value for a procedural assignment.\n24: error: 'f' is not a valid l-value for a procedural assignment.\n18: error: 'f' is not a valid l-value for a procedural assignment.\n20: error: 'f' is not a valid l-value for a procedural assignment.\n26: error: 'f' is not a valid l-value for a procedural assignment.\n14: error: 'f' is not a valid l-value for a procedural assignment.\n5: : 'f' is declared here as a wire.\n16: error: 'f' is not a valid l-value for a procedural assignment.\n28: error: 'f' is not a valid l-value for a procedural assignment.\n"} {"task_id": "vector0", "description": "Build a circuit that has one 3-bit input, then outputs the same vector, and also splits it into three separate 1-bit outputs. Connect output o0 to the input vector's position 0, o1 to position 1, etc.", "module_header": "module top_module(\n\tinput [2:0] vec, \n\toutput [2:0] outv,\n\toutput o2,\n\toutput o1,\n\toutput o0\n);\n", "original_code": "module top_module(\n\tinput [2:0] vec, \n\toutput [2:0] outv,\n\toutput o2,\n\toutput o1,\n\toutput o0\n);\n assign outv = vec;\n assign o2 = vec2;\n assign o1 = vec1;\n assign o0 = vec0;\n\nendmodule", "error": "11: error: Unable to elaborate r-value: vec0\n11: error: Unable to bind wire/reg/memory `vec0' in `top_module'\n10: error: Unable to bind wire/reg/memory `vec1' in `top_module'\n9: error: Unable to elaborate r-value: vec2\n10: error: Unable to elaborate r-value: vec1\n9: error: Unable to bind wire/reg/memory `vec2' in `top_module'\n"} {"task_id": "vector100r", "description": "Given a 100-bit input vector [99:0], reverse its bit ordering.", "module_header": "module top_module (\n\tinput [99:0] in,\n\toutput reg [99:0] out\n);\n", "original_code": "module top_module (\n\tinput [99:0] in,\n\toutput reg [99:0] out\n);\n integer i;\n\n always @(*) begin\n // always block triggered when any input changes.\n // Perform bit reversal operation on input.\n for (i = 0; i < 100; i = i + 1) begin\n // Loop through each bit of the input.\n outi = ini;\n // Assign the input bit to the output in reversed order.\n end\n end\n\nendmodule", "error": "12: error: Could not find variable ``outi'' in ``top_module''\n"} {"task_id": "vector100r", "description": "Given a 100-bit input vector [99:0], reverse its bit ordering.", "module_header": "module top_module (\n\tinput [99:0] in,\n\toutput reg [99:0] out\n);\n", "original_code": "module top_module (\n\tinput [99:0] in,\n\toutput reg [99:0] out\n);\n reverse_module reverse_inst (\n .in(in),\n .out(out)\n );\n\nendmodule", "error": "5: error: Unknown module type: reverse_module\n"} {"task_id": "vector2", "description": "Build a circuit that reverses the byte order of a 32-bit vector.", "module_header": "module top_module (\n\tinput [31:0] in,\n\toutput [31:0] out\n);\n", "original_code": "module top_module (\n\tinput [31:0] in,\n\toutput [31:0] out\n);\n // Temporary 8-bit register\n reg [7:0] temp;\n\n // State transition logic\n always @(posedge clk) begin\n // Extract the four bytes\n temp[7:0] = in[7:0];\n temp[15:8] = in[15:8];\n temp[23:16] = in[23:16];\n temp[31:24] = in[31:24];\n\n // Reverse their order\n out[7:0] = temp[31:24];\n out[15:8] = temp[23:16];\n out[23:16] = temp[15:8];\n out[31:24] = temp[7:0];\n end\n\nendmodule", "error": "19: error: 'out['sd23:'sd16]' is not a valid l-value for a procedural assignment.\n3: : 'out['sd23:'sd16]' is declared here as a wire.\n20: error: 'out['sd31:'sd24]' is not a valid l-value for a procedural assignment.\n3: : 'out['sd7:'sd0]' is declared here as a wire.\n3: : 'out['sd15:'sd8]' is declared here as a wire.\n18: error: 'out['sd15:'sd8]' is not a valid l-value for a procedural assignment.\n12: warning: Part select temp[15:8] is out of range.\n3: : 'out['sd31:'sd24]' is declared here as a wire.\n13: warning: Part select temp[23:16] is out of range.\n9: error: Failed to evaluate event expression 'posedge clk'.\n17: error: 'out['sd7:'sd0]' is not a valid l-value for a procedural assignment.\n9: error: Unable to bind wire/reg/memory `clk' in `top_module'\n14: warning: Part select temp[31:24] is out of range.\n"} {"task_id": "vector2", "description": "Build a circuit that reverses the byte order of a 32-bit vector.", "module_header": "module top_module (\n\tinput [31:0] in,\n\toutput [31:0] out\n);\n", "original_code": "module top_module (\n\tinput [31:0] in,\n\toutput [31:0] out\n);\n string out_str;\n byte byte1;\n byte byte2;\n byte byte3;\n byte byte4;\n\n always @(*) begin\n byte1 = in[7:0];\n byte2 = in[15:8];\n byte3 = in[23:16];\n byte4 = in[31:24];\n\n out = {byte1, byte2, byte3, byte4};\n\n end\n\nendmodule", "error": "17: error: 'out' is not a valid l-value for a procedural assignment.\n3: : 'out' is declared here as a wire.\n"} {"task_id": "vector3", "description": "Given several input vectors, concatenate them together then split them up into several output vectors. There are six 5-bit input vectors: a, b, c, d, e, and f, for a total of 30 bits of input. There are four 8-bit output vectors: w, x, y, and z, for 32 bits of output. The output should be a concatenation of the input vectors followed by two 1 bits (the two 1 bits should be in the LSB positions).", "module_header": "module top_module (\n\tinput [4:0] a,\n\tinput [4:0] b,\n\tinput [4:0] c,\n\tinput [4:0] d,\n\tinput [4:0] e,\n\tinput [4:0] f,\n\toutput [7:0] w,\n\toutput [7:0] x,\n\toutput [7:0] y,\n\toutput [7:0] z\n);\n", "original_code": "module top_module (\n\tinput [4:0] a,\n\tinput [4:0] b,\n\tinput [4:0] c,\n\tinput [4:0] d,\n\tinput [4:0] e,\n\tinput [4:0] f,\n\toutput [7:0] w,\n\toutput [7:0] x,\n\toutput [7:0] y,\n\toutput [7:0] z\n);\n assign w = { a, b, c, d, e, f, 2'b11 };\n assign x = w[15:8];\n assign y = w[23:16];\n assign z = w[31:24];\n\nendmodule", "error": "16: : Replacing the out of bound bits with 'bx.\n16: warning: Part select [31:24] is selecting after the vector w[7:0].\n15: warning: Part select [23:16] is selecting after the vector w[7:0].\n15: : Replacing the out of bound bits with 'bx.\n14: : Replacing the out of bound bits with 'bx.\n14: warning: Part select [15:8] is selecting after the vector w[7:0].\n"} {"task_id": "vector3", "description": "Given several input vectors, concatenate them together then split them up into several output vectors. There are six 5-bit input vectors: a, b, c, d, e, and f, for a total of 30 bits of input. There are four 8-bit output vectors: w, x, y, and z, for 32 bits of output. The output should be a concatenation of the input vectors followed by two 1 bits (the two 1 bits should be in the LSB positions).", "module_header": "module top_module (\n\tinput [4:0] a,\n\tinput [4:0] b,\n\tinput [4:0] c,\n\tinput [4:0] d,\n\tinput [4:0] e,\n\tinput [4:0] f,\n\toutput [7:0] w,\n\toutput [7:0] x,\n\toutput [7:0] y,\n\toutput [7:0] z\n);\n", "original_code": "module top_module (\n\tinput [4:0] a,\n\tinput [4:0] b,\n\tinput [4:0] c,\n\tinput [4:0] d,\n\tinput [4:0] e,\n\tinput [4:0] f,\n\toutput [7:0] w,\n\toutput [7:0] x,\n\toutput [7:0] y,\n\toutput [7:0] z\n);\n assign w = {a, b, c, d, e, f, 2'b01};\n assign x = w[15:8];\n assign y = w[23:16];\n assign z = w[31:24];\n\nendmodule", "error": "16: : Replacing the out of bound bits with 'bx.\n16: warning: Part select [31:24] is selecting after the vector w[7:0].\n15: warning: Part select [23:16] is selecting after the vector w[7:0].\n15: : Replacing the out of bound bits with 'bx.\n14: : Replacing the out of bound bits with 'bx.\n14: warning: Part select [15:8] is selecting after the vector w[7:0].\n"} {"task_id": "vector4", "description": "One common place to see a replication operator is when sign-extending a smaller number to a larger one, while preserving its signed value. This is done by replicating the sign bit (the most significant bit) of the smaller number to the left. For example, sign-extending 4'b0101 (5) to 8 bits results in 8'b00000101 (5), while sign-extending 4'b1101 (-3) to 8 bits results in 8'b11111101 (-3). Build a circuit that sign-extends an 8-bit number to 32 bits. This requires a concatenation of 24 copies of the sign bit (i.e., replicate bit[7] 24 times) followed by the 8-bit number itself.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput [31:0] out\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput [31:0] out\n);\n sign_extend sign_extend_inst (\n .in(in),\n .out(out)\n );\n\n endmodule", "error": "5: error: Unknown module type: sign_extend\n"} {"task_id": "vector5", "description": "Given five 1-bit signals (a, b, c, d, and e), compute all 25 pairwise one-bit comparisons in the 25-bit output vector. The output should be 1 if the two bits being compared are equal. Example: out[24] = ~a ^ a; out[23] = ~a ^ b; out[22] = ~a ^ c; ... out[ 1] = ~e ^ d; out[ 0] = ~e ^ e.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\tinput e,\n\toutput [24:0] out\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\tinput e,\n\toutput [24:0] out\n);\n // 25-bit output vector\n\twire [24:0] out;\n\n\t// pairwise one-bit comparisons\n\tassign out[24] = ~a ^ a;\n\tassign out[23] = ~a ^ b;\n\tassign out[22] = ~a ^ c;\n\tassign out[21] = ~a ^ d;\n\tassign out[20] = ~a ^ e;\n\tassign out[19] = ~b ^ a;\n\tassign out[18] = ~b ^ b;\n\tassign out[17] = ~b ^ c;\n\tassign out[16] = ~b ^ d;\n\tassign out[15] = ~b ^ e;\n\tassign out[14] = ~c ^ a;\n\tassign out[13] = ~c ^ b;\n\tassign out[12] = ~c ^ c;\n\tassign out[11] = ~c ^ d;\n\tassign out[10] = ~c ^ e;\n\tassign out[9] = ~d ^ a;\n\tassign out[8] = ~d ^ b;\n\tassign out[7] = ~d ^ c;\n\tassign out[6] = ~d ^ d;\n\tassign out[5] = ~d ^ e;\n\tassign out[4] = ~e ^ a;\n\tassign out[3] = ~e ^ b;\n\tassign out[2] = ~e ^ c;\n\tassign out[1] = ~e ^ d;\n\tassign out[0] = ~e ^ e;\n\nendmodule", "error": "10: error: 'out' has already been declared in this scope.\n7: : It was declared here as a net.\n"} {"task_id": "vector5", "description": "Given five 1-bit signals (a, b, c, d, and e), compute all 25 pairwise one-bit comparisons in the 25-bit output vector. The output should be 1 if the two bits being compared are equal. Example: out[24] = ~a ^ a; out[23] = ~a ^ b; out[22] = ~a ^ c; ... out[ 1] = ~e ^ d; out[ 0] = ~e ^ e.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\tinput e,\n\toutput [24:0] out\n);\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\tinput e,\n\toutput [24:0] out\n);\n always @(*) begin\n out[24] = ~a ^ e;\n out[23] = ~a ^ d;\n out[22] = ~a ^ c;\n out[21] = ~a ^ b;\n out[20] = ~b ^ e;\n out[19] = ~b ^ d;\n out[18] = ~b ^ c;\n out[17] = ~b ^ a;\n out[16] = ~c ^ e;\n out[15] = ~c ^ d;\n out[14] = ~c ^ b;\n out[13] = ~c ^ a;\n out[12] = ~d ^ e;\n out[11] = ~d ^ b;\n out[10] = ~d ^ a;\n out[9] = ~e ^ c;\n out[8] = ~e ^ b;\n out[7] = ~e ^ a;\n out[6] = b ^ c;\n out[5] = b ^ d;\n out[4] = b ^ e;\n out[3] = c ^ d;\n out[2] = c ^ e;\n out[1] = d ^ e;\n out[0] = e ^ e;\n end\n\nendmodule", "error": "7: : 'out['sd13]' is declared here as a wire.\n23: error: 'out['sd11]' is not a valid l-value for a procedural assignment.\n29: error: 'out['sd5]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd11]' is declared here as a wire.\n15: error: 'out['sd19]' is not a valid l-value for a procedural assignment.\n31: error: 'out['sd3]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd23]' is declared here as a wire.\n7: : 'out['sd7]' is declared here as a wire.\n7: : 'out['sd16]' is declared here as a wire.\n21: error: 'out['sd13]' is not a valid l-value for a procedural assignment.\n19: error: 'out['sd15]' is not a valid l-value for a procedural assignment.\n27: error: 'out['sd7]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd1]' is declared here as a wire.\n7: : 'out['sd22]' is declared here as a wire.\n26: error: 'out['sd8]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd12]' is declared here as a wire.\n30: error: 'out['sd4]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd20]' is declared here as a wire.\n12: error: 'out['sd22]' is not a valid l-value for a procedural assignment.\n33: error: 'out['sd1]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd8]' is declared here as a wire.\n7: : 'out['sd17]' is declared here as a wire.\n16: error: 'out['sd18]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd19]' is declared here as a wire.\n7: : 'out['sd0]' is declared here as a wire.\n11: error: 'out['sd23]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd9]' is declared here as a wire.\n7: : 'out['sd18]' is declared here as a wire.\n7: : 'out['sd21]' is declared here as a wire.\n7: : 'out['sd5]' is declared here as a wire.\n18: error: 'out['sd16]' is not a valid l-value for a procedural assignment.\n22: error: 'out['sd12]' is not a valid l-value for a procedural assignment.\n10: error: 'out['sd24]' is not a valid l-value for a procedural assignment.\n34: error: 'out['sd0]' is not a valid l-value for a procedural assignment.\n17: error: 'out['sd17]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd10]' is declared here as a wire.\n13: error: 'out['sd21]' is not a valid l-value for a procedural assignment.\n20: error: 'out['sd14]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd6]' is declared here as a wire.\n7: : 'out['sd3]' is declared here as a wire.\n7: : 'out['sd4]' is declared here as a wire.\n7: : 'out['sd24]' is declared here as a wire.\n32: error: 'out['sd2]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd15]' is declared here as a wire.\n9: warning: @* found no sensitivities so it will never trigger.\n25: error: 'out['sd9]' is not a valid l-value for a procedural assignment.\n7: : 'out['sd14]' is declared here as a wire.\n7: : 'out['sd2]' is declared here as a wire.\n28: error: 'out['sd6]' is not a valid l-value for a procedural assignment.\n14: error: 'out['sd20]' is not a valid l-value for a procedural assignment.\n24: error: 'out['sd10]' is not a valid l-value for a procedural assignment.\n"} {"task_id": "vectorgates", "description": "Build a circuit that has two 3-bit inputs that computes the bitwise-OR of the two vectors, the logical-OR of the two vectors, and the inverse (NOT) of both vectors. Place the inverse of b in the upper half of out_not (i.e., bits [5:3]), and the inverse of a in the lower half.", "module_header": "module top_module(\n\tinput [2:0] a, \n\tinput [2:0] b, \n\toutput [2:0] out_or_bitwise,\n\toutput out_or_logical,\n\toutput [5:0] out_not\n);\n", "original_code": "module top_module(\n\tinput [2:0] a, \n\tinput [2:0] b, \n\toutput [2:0] out_or_bitwise,\n\toutput out_or_logical,\n\toutput [5:0] out_not\n);\n\n reg [2:0] a_reg;\n reg [2:0] b_reg;\n reg [2:0] out_or_bitwise_reg;\n reg out_or_logical_reg;\n reg [5:0] out_not_reg;\n\n always @(posedge clk) begin\n a_reg <= a;\n b_reg <= b;\n out_or_bitwise_reg <= a_reg | b_reg;\n out_or_logical_reg <= |(a_reg | b_reg);\n out_not_reg[5:3] <= ~b_reg;\n out_not_reg[2:0] <= ~a_reg;\n end\n\n assign out_or_bitwise = out_or_bitwise_reg;\n assign out_or_logical = out_or_logical_reg;\n assign out_not = out_not_reg;\n\nendmodule", "error": "15: error: Failed to evaluate event expression 'posedge clk'.\n15: error: Unable to bind wire/reg/memory `clk' in `top_module'\n"} {"task_id": "vectorr", "description": "Given an 8-bit input vector [7:0], reverse its bit ordering.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput [7:0] out\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput [7:0] out\n);\n assign out = {in0, in1, in2, in3, in4, in5, in6, in7};\n\nendmodule", "error": "5: error: Unable to bind wire/reg/memory `in0' in `top_module'\n5: error: Unable to bind wire/reg/memory `in2' in `top_module'\n5: error: Unable to bind wire/reg/memory `in1' in `top_module'\n5: error: Unable to bind wire/reg/memory `in5' in `top_module'\n5: error: Unable to elaborate r-value: {in0, in1, in2, in3, in4, in5, in6, in7}\n5: error: Unable to bind wire/reg/memory `in3' in `top_module'\n5: error: Unable to bind wire/reg/memory `in4' in `top_module'\n5: error: Concatenation/replication may not have zero width in this context.\n5: error: Unable to bind wire/reg/memory `in6' in `top_module'\n5: error: Unable to bind wire/reg/memory `in7' in `top_module'\n"} {"task_id": "vectorr", "description": "Given an 8-bit input vector [7:0], reverse its bit ordering.", "module_header": "module top_module (\n\tinput [7:0] in,\n\toutput [7:0] out\n);\n", "original_code": "module top_module (\n\tinput [7:0] in,\n\toutput [7:0] out\n);\n integer i;\n reg [7:0] temp;\n\n always @(*) begin\n for (i = 0; i < 8; i = i + 1) begin\n temp[i] = in[7-i];\n end\n out = temp;\n end\n\nendmodule", "error": "12: error: 'out' is not a valid l-value for a procedural assignment.\n3: : 'out' is declared here as a wire.\n"} {"task_id": "wire4", "description": "Create a module with 3 inputs and 4 outputs that behaves like wires that makes these connections: a -> w\n// ; b -> x; b -> y; c -> z.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\toutput w,\n\toutput x,\n\toutput y,\n\toutput z );\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\toutput w,\n\toutput x,\n\toutput y,\n\toutput z );\n wire a;\n wire b;\n wire c;\n wire w;\n wire x;\n wire y;\n wire z;\n\n assign w = a;\n assign x = b;\n assign y = b;\n assign z = c;\n\nendmodule", "error": "14: error: 'y' has already been declared in this scope.\n4: : It was declared here as a net.\n15: error: 'z' has already been declared in this scope.\n2: : It was declared here as a net.\n8: : It was declared here as a net.\n13: error: 'x' has already been declared in this scope.\n9: error: 'a' has already been declared in this scope.\n10: error: 'b' has already been declared in this scope.\n5: : It was declared here as a net.\n12: error: 'w' has already been declared in this scope.\n7: : It was declared here as a net.\n11: error: 'c' has already been declared in this scope.\n3: : It was declared here as a net.\n6: : It was declared here as a net.\n"} {"task_id": "wire_decl", "description": "Implement the following circuit. Create two intermediate wires (named anything you want) to connect the AND and OR gates together. Note that the wire that feeds the NOT gate is really wire `out`, so you do not necessarily need to declare a third wire here. Notice how wires are driven by exactly one source (output of a gate), but can feed multiple inputs.\n\n// The circuit is composed of two layers. The first layer, counting from the input, is two AND gates: one whose input is connected to a and b, and the second is connected to c and d. The second layer there is an OR gate to OR the two AND outputs, connected the output 'out'. Additionally, there is an inverted output 'out_n'.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out,\n\toutput out_n );\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out,\n\toutput out_n );\n wire and0_out;\n wire and1_out;\n wire or0_out;\n\n and and0 (\n .a(a),\n .b(b),\n .out(and0_out)\n );\n\n and and1 (\n .a(c),\n .b(d),\n .out(and1_out)\n );\n\n or or0 (\n .a(and0_out),\n .b(and1_out),\n .out(or0_out)\n );\n\n not not0 (\n .a(or0_out),\n .out(out_n)\n );\n\n buf buf0 (\n .in(or0_out),\n .out(out)\n );\n\n endmodule", "error": "30: error: Gates do not have port names.\n24: error: Gates do not have port names.\n35: error: Gates do not have port names.\n18: error: Gates do not have port names.\n12: error: Gates do not have port names.\n"} {"task_id": "wire_decl", "description": "Implement the following circuit. Create two intermediate wires (named anything you want) to connect the AND and OR gates together. Note that the wire that feeds the NOT gate is really wire `out`, so you do not necessarily need to declare a third wire here. Notice how wires are driven by exactly one source (output of a gate), but can feed multiple inputs.\n\n// The circuit is composed of two layers. The first layer, counting from the input, is two AND gates: one whose input is connected to a and b, and the second is connected to c and d. The second layer there is an OR gate to OR the two AND outputs, connected the output 'out'. Additionally, there is an inverted output 'out_n'.", "module_header": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out,\n\toutput out_n );\n", "original_code": "module top_module (\n\tinput a,\n\tinput b,\n\tinput c,\n\tinput d,\n\toutput out,\n\toutput out_n );\n wire and0_out;\n wire and1_out;\n wire or0_out;\n\n and and0 (\n .a(a),\n .b(b),\n .o(and0_out)\n );\n and and1 (\n .a(c),\n .b(d),\n .o(and1_out)\n );\n or or0 (\n .a(and0_out),\n .b(and1_out),\n .o(or0_out)\n );\n assign out = or0_out;\n assign out_n = ~or0_out;\n endmodule", "error": "17: error: Gates do not have port names.\n22: error: Gates do not have port names.\n12: error: Gates do not have port names.\n"} {"task_id": "zero", "description": "Build a circuit that always outputs a LOW.", "module_header": "module top_module(\n\toutput zero);\n", "original_code": "module top_module(\n\toutput zero);\n // Output port is declared as\n // a wire since it is not connected to\n // any of the logic elements in the design\n wire zero;\n\n // Assigning a constant value of 1'b0 to the output port\n assign zero = 1'b0;\n\n endmodule", "error": "2: : It was declared here as a net.\n6: error: 'zero' has already been declared in this scope.\n"} {"task_id": "zero", "description": "Build a circuit that always outputs a LOW.", "module_header": "module top_module(\n\toutput zero);\n", "original_code": "module top_module(\n\toutput zero);\n // Output port is declared as\n // a wire.\n\twire zero;\n\n\tassign zero = 1'b0;\n\n\tendmodule", "error": "2: : It was declared here as a net.\n5: error: 'zero' has already been declared in this scope.\n"}