task_id: wire

prompt:
module top_module(
	input in,
	output out);

canonical_solution:
	assign out = in;

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input in,
	output out);

	assign out = in;

endmodule

module stimulus_gen (
	input clk,
	output reg in,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		wavedrom_start("Output should follow input");
		repeat(20) @(posedge clk, negedge clk)
			in <= $random;
		wavedrom_stop();
		repeat(100) @(posedge clk, negedge clk) begin
			in <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_out;
		int errortime_out;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic in;
	logic out_ref;
	logic out_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,in,out_ref,out_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in );
	reference_module good1 (
		.in,
		.out(out_ref) );

	top_module top_module1 (
		.in,
		.out(out_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_out) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out", stats1.errors_out, stats1.errortime_out);
		else $display("Hint: Output '%s' has no mismatches.", "out");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { out_ref } === ( { out_ref } ^ { out_dut } ^ { out_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (out_ref !== ( out_ref ^ out_dut ^ out_ref ))
		begin if (stats1.errors_out == 0) stats1.errortime_out = $time;
			stats1.errors_out = stats1.errors_out+1'b1; end

	end
endmodule

simple_description: the top module 	to the stimulus_gen, and every output of the top module to the top module.

detail_description: the top module to the output of the stimulus_gen module. The top module is the module that is being tested.  	The top module contains two inputs, a clock and a reset. The clock is used to synchronize the logic of the module. The reset is used to reset the state of the module. The module also contains two outputs, a data output and a valid output. The data output is used to output the data that is being processed by the module, and the valid output is used to indicate when the data output is valid.  	The top module also contains two internal signals, a state and a counter. The state is used to keep track of the current state of the module, and the counter is used to keep track of the number of clock cycles that have passed since the last reset.  	The top module is a finite state machine (FSM). The FSM has four states: idle, wait, process, and done. The idle state is the initial state of the module, and is entered when the reset signal is asserted. In the idle state, the counter is reset to 0 and the data output is set to 0.  	When the clock signal is asserted, the FSM transitions to the wait state. In the wait state, the counter is incremented and the data output is set to 0. The FSM remains in the wait state until the counter reaches a certain threshold, at which point it transitions to the process state.  	In the process state, the data output is set to the data that is being processed by the module. The FSM then transitions to the done state. In the done state, the valid output is asserted to indicate that the data output is valid. The FSM then transitions back to the idle state.


prompt:
module top_module(
	input clk,
	input reset,
	output shift_ena);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input reset,
	output shift_ena);

	parameter B0=0, B1=1, B2=2, B3=3, Done=4;

	reg [2:0] state, next;

	always_comb begin
		case (state)
			B0: next = B1;
			B1: next = B2;
			B2: next = B3;
			B3: next = Done;
			Done: next = Done;
		endcase
	end

	always @(posedge clk)
		if (reset) state <= B0;
		else state <= next;

	assign shift_ena = (state == B0 || state == B1 || state == B2 || state == B3);

endmodule

module stimulus_gen (
	input clk,
	output reg reset
);

	initial begin
		repeat(100) @(posedge clk, negedge clk) begin
			reset <= !($random & 31);
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_shift_ena;
		int errortime_shift_ena;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic reset;
	logic shift_ena_ref;
	logic shift_ena_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,reset,shift_ena_ref,shift_ena_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.reset );
	reference_module good1 (
		.clk,
		.reset,
		.shift_ena(shift_ena_ref) );

	top_module top_module1 (
		.clk,
		.reset,
		.shift_ena(shift_ena_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_shift_ena) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "shift_ena", stats1.errors_shift_ena, stats1.errortime_shift_ena);
		else $display("Hint: Output '%s' has no mismatches.", "shift_ena");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { shift_ena_ref } === ( { shift_ena_ref } ^ { shift_ena_dut } ^ { shift_ena_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (shift_ena_ref !== ( shift_ena_ref ^ shift_ena_dut ^ shift_ena_ref ))
		begin if (stats1.errors_shift_ena == 0) stats1.errortime_shift_ena = $time;
			stats1.errors_shift_ena = stats1.errors_shift_ena+1'b1; end

	end
endmodule

detail_description:
The top module contains a 3 bit state register with the following state transition:

B0 -> B1 -> B2 -> B3 -> Done

B0 indicates that it is the first shift cycle.
B1 indicates that it is the second shift cycle.
B2 indicates that it is the third shift cycle.
B3 indicates that it is the fourth shift cycle.
Done indicates that it has completed the fourth shift cycle.

When the reset is 1, it will always go to state B0.
When the reset is 0, and state is not B0, B1, B2, or B3, it is in state Done.
shift_ena will be 1 if state is B0, B1, B2, or B3.


prompt:
module top_module(
	input clk,
	input reset,
	output reg [3:0] q);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input reset,
	output reg [3:0] q);

	always @(posedge clk)
		if (reset)
			q <= 0;
		else
			q <= q+1;

endmodule

module stimulus_gen (
	input clk,
	output reg reset,
	input tb_match,
	output reg wavedrom_enable,
	output reg[511:0] wavedrom_title
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	task reset_test(input async=0);
		bit arfail, srfail, datafail;

		@(posedge clk);
		@(posedge clk) reset <= 0;
		repeat(3) @(posedge clk);

		@(negedge clk) begin datafail = !tb_match ; reset <= 1; end
		@(posedge clk) arfail = !tb_match;
		@(posedge clk) begin
			srfail = !tb_match;
			reset <= 0;
		end
		if (srfail)
			$display("Hint: Your reset doesn't seem to be working.");
		else if (arfail && (async || !datafail))
			$display("Hint: Your reset should be %0s, but doesn't appear to be.", async ? "asynchronous" : "synchronous");
		// Don't warn about synchronous reset if the half-cycle before is already wrong. It's more likely
		// a functionality error than the reset being implemented asynchronously.

	endtask

	initial begin
		reset <= 1;
		@(negedge clk);

		wavedrom_start("Reset and counting");
		reset_test();

		repeat(3) @(posedge clk);
		wavedrom_stop();

		repeat(400) @(posedge clk, negedge clk) begin
			reset <= !($random & 31);
		end
		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic reset;
	logic [3:0] q_ref;
	logic [3:0] q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,reset,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.reset );
	reference_module good1 (
		.clk,
		.reset,
		.q(q_ref) );

	top_module top_module1 (
		.clk,
		.reset,
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { q_ref } === ( { q_ref } ^ { q_dut } ^ { q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

simple_description: This module increments the 4-bit output q on the positive edge of the clock, resetting to 0 when reset is asserted.

detail_description: This Verilog module is a simple 4-bit counter. It has three inputs: clk, reset, and q. The clk input is a clock signal, which is used to trigger the counter to increment. The reset input is a signal that, when asserted, will reset the counter to 0. The q output is a 4-bit register that holds the current value of the counter.  The module is implemented using an always block. This block is triggered on the rising edge of the clk signal. When the block is triggered, it first checks the reset signal. If the reset signal is asserted, the counter is reset to 0. Otherwise, the counter is incremented by 1. The incremented value is then stored in the q register.


prompt:
module top_module (
	input a,
	input b,
	input sel_b1,
	input sel_b2,
	output out_assign,
	output reg out_always
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input a,
	input b,
	input sel_b1,
	input sel_b2,
	output out_assign,
	output reg out_always
);

	assign out_assign = (sel_b1 & sel_b2) ? b : a;
	always @(*) out_always = (sel_b1 & sel_b2) ? b : a;

endmodule

module stimulus_gen (
	input clk,
	output logic a,b,sel_b1, sel_b2,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		{a, b, sel_b1, sel_b2} <= 4'b000;
		@(negedge clk) wavedrom_start("");
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0100;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1000;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1101;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0001;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0110;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1010;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1111;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0011;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0111;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1011;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b1111;
			@(posedge clk, negedge clk) {a,b,sel_b1,sel_b2} <= 4'b0011;
		wavedrom_stop();
		repeat(100) @(posedge clk, negedge clk)
			{a,b,sel_b1,sel_b2} <= $urandom;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_out_assign;
		int errortime_out_assign;
		int errors_out_always;
		int errortime_out_always;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic a;
	logic b;
	logic sel_b1;
	logic sel_b2;
	logic out_assign_ref;
	logic out_assign_dut;
	logic out_always_ref;
	logic out_always_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,a,b,sel_b1,sel_b2,out_assign_ref,out_assign_dut,out_always_ref,out_always_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.a,
		.b,
		.sel_b1,
		.sel_b2 );
	reference_module good1 (
		.a,
		.b,
		.sel_b1,
		.sel_b2,
		.out_assign(out_assign_ref),
		.out_always(out_always_ref) );

	top_module top_module1 (
		.a,
		.b,
		.sel_b1,
		.sel_b2,
		.out_assign(out_assign_dut),
		.out_always(out_always_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_out_assign) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out_assign", stats1.errors_out_assign, stats1.errortime_out_assign);
		else $display("Hint: Output '%s' has no mismatches.", "out_assign");
		if (stats1.errors_out_always) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out_always", stats1.errors_out_always, stats1.errortime_out_always);
		else $display("Hint: Output '%s' has no mismatches.", "out_always");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { out_assign_ref, out_always_ref } === ( { out_assign_ref, out_always_ref } ^ { out_assign_dut, out_always_dut } ^ { out_assign_ref, out_always_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (out_assign_ref !== ( out_assign_ref ^ out_assign_dut ^ out_assign_ref ))
		begin if (stats1.errors_out_assign == 0) stats1.errortime_out_assign = $time;
			stats1.errors_out_assign = stats1.errors_out_assign+1'b1; end
		if (out_always_ref !== ( out_always_ref ^ out_always_dut ^ out_always_ref ))
		begin if (stats1.errors_out_always == 0) stats1.errortime_out_always = $time;
			stats1.errors_out_always = stats1.errors_out_always+1'b1; end

	end
endmodule

simple_description: This module assigns the value of either 'a' or 'b' to the outputs 'out_assign' and 'out_always' depending on the values of 'sel_b1' and 'sel_b2'.

detail_description: This top Verilog module has two outputs, out_assign and out_always, and four inputs, a, b, sel_b1, and sel_b2. The module is used to select either input a or input b depending on the values of sel_b1 and sel_b2.   The out_assign output is assigned the value of either input a or input b using an assign statement. If both sel_b1 and sel_b2 are 1, then the output is assigned the value of input b. Otherwise, the output is assigned the value of input a.   The out_always output is also assigned the value of either input a or input b, but it is done using an always block. This means that the output will be updated whenever the values of the inputs change. If both sel_b1 and sel_b2 are 1, then the output is assigned the value of input b. Otherwise, the output is assigned the value of input a.


prompt:
module top_module(
	input a,
	input b,
	input c,
	output out
);

canonical_solution:
	assign out = (a | b | c);

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input a,
	input b,
	input c,
	output out
);

	assign out = (a | b | c);

endmodule

module stimulus_gen (
	input clk,
	output reg a, b, c,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		int count; count = 0;
		{a,b,c} <= 1'b0;
		wavedrom_start();
		repeat(10) @(posedge clk)
			{a,b,c} <= count++;
		wavedrom_stop();

		repeat(200) @(posedge clk, negedge clk)
			{c,b,a} <= $urandom;

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_out;
		int errortime_out;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic a;
	logic b;
	logic c;
	logic out_ref;
	logic out_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,a,b,c,out_ref,out_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.a,
		.b,
		.c );
	reference_module good1 (
		.a,
		.b,
		.c,
		.out(out_ref) );

	top_module top_module1 (
		.a,
		.b,
		.c,
		.out(out_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_out) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out", stats1.errors_out, stats1.errortime_out);
		else $display("Hint: Output '%s' has no mismatches.", "out");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { out_ref } === ( { out_ref } ^ { out_dut } ^ { out_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (out_ref !== ( out_ref ^ out_dut ^ out_ref ))
		begin if (stats1.errors_out == 0) stats1.errortime_out = $time;
			stats1.errors_out = stats1.errors_out+1'b1; end

	end
endmodule

simple_description: This module assigns the output 'out' to the logical OR of inputs 'a', 'b', and 'c'.

detail_description: This Verilog module is a simple logic gate that performs a logical OR operation on the three inputs a, b, and c and assigns the result to the output out. The OR operation is a binary operation that returns a true value if one or more of its inputs are true. In this module, the output out will be true if any of the inputs a, b, or c are true. If all of the inputs are false, then the output out will be false. The module is composed of a single assign statement that performs the OR operation on the inputs and assigns the result to the output out.


prompt:
module top_module (
	input clk,
	input resetn,
	input [3:1] r,
	output [3:1] g
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clk,
	input resetn,
	input [3:1] r,
	output [3:1] g
);
	parameter A=0, B=1, C=2, D=3;
	reg [1:0] state, next;

	always @(posedge clk) begin
		if (~resetn) state <= A;
		else state <= next;
	end

	always@(state,r) begin
		case (state)
			A: if (r[1]) next = B;
			   else if (r[2]) next = C;
			   else if (r[3]) next = D;
			   else next = A;
			B: next = r[1] ? B : A;
			C: next = r[2] ? C : A;
			D: next = r[3] ? D : A;
			default: next = 'x;
		endcase
	end

	assign g[1] = (state == B);
	assign g[2] = (state == C);
	assign g[3] = (state == D);
endmodule

module stimulus_gen (
	input clk,
	output logic resetn,
	output logic [3:1] r,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable,
	input tb_match
);
	reg reset;
	assign resetn = ~reset;

	task reset_test(input async=0);
		bit arfail, srfail, datafail;

		@(posedge clk);
		@(posedge clk) reset <= 0;
		repeat(3) @(posedge clk);

		@(negedge clk) begin datafail = !tb_match ; reset <= 1; end
		@(posedge clk) arfail = !tb_match;
		@(posedge clk) begin
			srfail = !tb_match;
			reset <= 0;
		end
		if (srfail)
			$display("Hint: Your reset doesn't seem to be working.");
		else if (arfail && (async || !datafail))
			$display("Hint: Your reset should be %0s, but doesn't appear to be.", async ? "asynchronous" : "synchronous");
		// Don't warn about synchronous reset if the half-cycle before is already wrong. It's more likely
		// a functionality error than the reset being implemented asynchronously.

	endtask

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		reset <= 1;
		r <= 0;
		@(posedge clk);

		r <= 1;
		reset_test();

		r <= 0;
		wavedrom_start("");
		@(posedge clk) r <= 0;
		@(posedge clk) r <= 7;
		@(posedge clk) r <= 7;
		@(posedge clk) r <= 7;
		@(posedge clk) r <= 6;
		@(posedge clk) r <= 6;
		@(posedge clk) r <= 6;
		@(posedge clk) r <= 4;
		@(posedge clk) r <= 4;
		@(posedge clk) r <= 4;
		@(posedge clk) r <= 0;
		@(posedge clk) r <= 0;
		@(posedge clk) r <= 4;
		@(posedge clk) r <= 6;
		@(posedge clk) r <= 7;
		@(posedge clk) r <= 7;
		@(posedge clk) r <= 7;
		@(negedge clk);
		wavedrom_stop();

		@(posedge clk);
		reset <= 0;
		@(posedge clk);
		@(posedge clk);

		repeat(500) @(posedge clk, negedge clk) begin
			reset <= ($random & 63) == 0;
			r <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_g;
		int errortime_g;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic resetn;
	logic [3:1] r;
	logic [3:1] g_ref;
	logic [3:1] g_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,resetn,r,g_ref,g_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.resetn,
		.r );
	reference_module good1 (
		.clk,
		.resetn,
		.r,
		.g(g_ref) );

	top_module top_module1 (
		.clk,
		.resetn,
		.r,
		.g(g_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_g) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "g", stats1.errors_g, stats1.errortime_g);
		else $display("Hint: Output '%s' has no mismatches.", "g");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { g_ref } === ( { g_ref } ^ { g_dut } ^ { g_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (g_ref !== ( g_ref ^ g_dut ^ g_ref ))
		begin if (stats1.errors_g == 0) stats1.errortime_g = $time;
			stats1.errors_g = stats1.errors_g+1'b1; end

	end
endmodule

simple_description: This module implements a state machine that transitions between four states based on the input signals r[3:1] and the clock signal.

detail_description: The top Verilog module is a state machine that has 4 states, A, B, C, and D. The inputs to the module are a clock signal (clk), a reset signal (resetn), and a 3-bit vector (r). The outputs of the module are a 3-bit vector (g).   The module has a register, state, that stores the current state of the machine. The register is updated on the rising edge of the clock signal. If the reset signal is low, the state register is set to A. Otherwise, the state register is set to the value of the next register.  The next register stores the next state of the machine. It is updated in the always block. The logic for the next register is a case statement that depends on the current state and the 3-bit vector, r. If the current state is A, then the next state is determined by the value of r. If r[1] is high, then the next state is B. If r[2] is high, then the next state is C. If r[3] is high, then the next state is D. If none of the bits of r are high, then the next state is A. If the current state is B, then the next state is B if r[1] is high, otherwise the next state is A. If the current state is C, then the next state is C if r[2] is high, otherwise the next state is A. If the current state is D, then the next state is D if r[3] is high, otherwise the next state is A.  The 3-bit vector, g, is assigned based on the current state of the machine. If the current state is B, then g[1] is high. If the current state is C, then g[2] is high. If the current state is D, then g[3] is high. Otherwise, all the bits of g are low.


prompt:
module top_module(
	input clk,
	input reset,
	output reg [3:0] q);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input reset,
	output reg [3:0] q);

	always @(posedge clk)
		if (reset || q == 9)
			q <= 0;
		else
			q <= q+1;

endmodule

module stimulus_gen (
	input clk,
	output reg reset,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable,
	input tb_match
);

	task reset_test(input async=0);
		bit arfail, srfail, datafail;

		@(posedge clk);
		@(posedge clk) reset <= 0;
		repeat(3) @(posedge clk);

		@(negedge clk) begin datafail = !tb_match ; reset <= 1; end
		@(posedge clk) arfail = !tb_match;
		@(posedge clk) begin
			srfail = !tb_match;
			reset <= 0;
		end
		if (srfail)
			$display("Hint: Your reset doesn't seem to be working.");
		else if (arfail && (async || !datafail))
			$display("Hint: Your reset should be %0s, but doesn't appear to be.", async ? "asynchronous" : "synchronous");
		// Don't warn about synchronous reset if the half-cycle before is already wrong. It's more likely
		// a functionality error than the reset being implemented asynchronously.

	endtask

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		reset <= 1;
		wavedrom_start("Synchronous reset and counting");
		reset_test();
		repeat(12) @(posedge clk);
		wavedrom_stop();
		@(posedge clk);

		repeat(400) @(posedge clk, negedge clk) begin
			reset <= !($random & 31);
		end
		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic reset;
	logic [3:0] q_ref;
	logic [3:0] q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,reset,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.reset );
	reference_module good1 (
		.clk,
		.reset,
		.q(q_ref) );

	top_module top_module1 (
		.clk,
		.reset,
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { q_ref } === ( { q_ref } ^ { q_dut } ^ { q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

simple_description: This module increments the 4-bit output q on each rising edge of the clock, resetting it to 0 when reset is asserted or when q reaches 9.

detail_description: This Verilog module is a simple counter. It has one input, clk, one output, q, and one reset input. The clk input is used to trigger the counter. The reset input is used to reset the counter to 0. The output q is a 4-bit register that stores the current count value.  The module has an always block that is triggered on the positive edge of the clk signal. Inside the always block, an if-else statement is used to determine the next value of q. If the reset input is asserted or the current value of q is equal to 9, then q is reset to 0. Otherwise, q is incremented by 1.


prompt:
module top_module (
	input clk,
	input [7:0] in,
	input reset,
	output done
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clk,
	input [7:0] in,
	input reset,
	output done
);
	parameter BYTE1=0, BYTE2=1, BYTE3=2, DONE=3;
	reg [1:0] state;
	reg [1:0] next;

    wire in3 = in[3];

    always_comb begin
		case (state)
			BYTE1: next = in3 ? BYTE2 : BYTE1;
			BYTE2: next = BYTE3;
			BYTE3: next = DONE;
			DONE: next = in3 ? BYTE2 : BYTE1;
		endcase
    end

    always @(posedge clk) begin
		if (reset) state <= BYTE1;
        else state <= next;
	end

	assign done = (state==DONE);

endmodule

module stimulus_gen (
	input clk,
	output logic [7:0] in,
	output logic reset
);

	initial begin
		repeat(200) @(posedge clk, negedge clk) begin
			in <= $random;
			reset <= !($random & 31);
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_done;
		int errortime_done;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [7:0] in;
	logic reset;
	logic done_ref;
	logic done_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,in,reset,done_ref,done_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in,
		.reset );
	reference_module good1 (
		.clk,
		.in,
		.reset,
		.done(done_ref) );

	top_module top_module1 (
		.clk,
		.in,
		.reset,
		.done(done_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_done) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "done", stats1.errors_done, stats1.errortime_done);
		else $display("Hint: Output '%s' has no mismatches.", "done");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { done_ref } === ( { done_ref } ^ { done_dut } ^ { done_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (done_ref !== ( done_ref ^ done_dut ^ done_ref ))
		begin if (stats1.errors_done == 0) stats1.errortime_done = $time;
			stats1.errors_done = stats1.errors_done+1'b1; end

	end
endmodule

simple_description: This module implements a finite state machine that cycles through three states and outputs a done signal when the third state is reached.

detail_description: This top module is a state machine that takes in an 8-bit input and outputs a done signal when the third bit of the input is 1. The module has four states: BYTE1, BYTE2, BYTE3 and DONE. The state machine is clocked by the clk signal and reset by the reset signal.  The state machine starts in the BYTE1 state. In this state, the module checks the third bit of the input. If it is 0, the state machine remains in the BYTE1 state. If it is 1, the state machine transitions to the BYTE2 state.  In the BYTE2 state, the state machine transitions to the BYTE3 state. In the BYTE3 state, the state machine transitions to the DONE state.  In the DONE state, the module checks the third bit of the input again. If it is 0, the state machine transitions back to the BYTE1 state. If it is 1, the state machine transitions back to the BYTE2 state.  The done signal is asserted when the state machine is in the DONE state.


prompt:
module top_module (
	input a,
	input b,
	input sel,
	output out
);

canonical_solution:
	assign out = sel ? b : a;

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input a,
	input b,
	input sel,
	output out
);

	assign out = sel ? b : a;

endmodule

module stimulus_gen (
	input clk,
	output logic a,b,sel,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		{a, b, sel} <= 3'b000;
		@(negedge clk) wavedrom_start("Sel chooses between a and b");
			@(posedge clk) {a, b, sel} <= 3'b000;
			@(posedge clk) {a, b, sel} <= 3'b100;
			@(posedge clk) {a, b, sel} <= 3'b110;
			@(posedge clk) {a, b, sel} <= 3'b111;
			@(posedge clk) {a, b, sel} <= 3'b011;
			@(posedge clk) {a, b, sel} <= 3'b001;
			@(posedge clk) {a, b, sel} <= 3'b100;
			@(posedge clk) {a, b, sel} <= 3'b101;
			@(posedge clk) {a, b, sel} <= 3'b110;
			@(posedge clk) {a, b, sel} <= 3'b111;
		@(negedge clk) wavedrom_stop();
		repeat(100) @(posedge clk, negedge clk)
			{a,b,sel} <= $random;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_out;
		int errortime_out;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic a;
	logic b;
	logic sel;
	logic out_ref;
	logic out_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,a,b,sel,out_ref,out_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.a,
		.b,
		.sel );
	reference_module good1 (
		.a,
		.b,
		.sel,
		.out(out_ref) );

	top_module top_module1 (
		.a,
		.b,
		.sel,
		.out(out_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_out) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out", stats1.errors_out, stats1.errortime_out);
		else $display("Hint: Output '%s' has no mismatches.", "out");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { out_ref } === ( { out_ref } ^ { out_dut } ^ { out_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (out_ref !== ( out_ref ^ out_dut ^ out_ref ))
		begin if (stats1.errors_out == 0) stats1.errortime_out = $time;
			stats1.errors_out = stats1.errors_out+1'b1; end

	end
endmodule

simple_description: This module assigns the output to either input a or b depending on the value of the select signal.

detail_description: This Verilog module is a simple multiplexer. It takes two inputs, a and b, as well as a selector input, sel. It then outputs the value of either a or b, depending on the value of sel. If sel is 1, the output will be b, and if sel is 0, the output will be a. This module is useful for selecting between two different values, depending on the value of the selector.


prompt:
module top_module (
	input [3:0] in,
	output out_and,
	output out_or,
	output out_xor
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input [3:0] in,
	output out_and,
	output out_or,
	output out_xor
);

	assign out_and = ∈
	assign out_or = |in;
	assign out_xor = ^in;

endmodule

module stimulus_gen (
	input clk,
	output logic [3:0] in,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		in <= 0;
		@(negedge clk) wavedrom_start("All combinations");
			@(posedge clk);
			repeat(15) @(posedge clk) in <= in + 1;
		@(negedge clk) wavedrom_stop();
		repeat(200) @(posedge clk, negedge clk)
			in <= $random;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_out_and;
		int errortime_out_and;
		int errors_out_or;
		int errortime_out_or;
		int errors_out_xor;
		int errortime_out_xor;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [3:0] in;
	logic out_and_ref;
	logic out_and_dut;
	logic out_or_ref;
	logic out_or_dut;
	logic out_xor_ref;
	logic out_xor_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,in,out_and_ref,out_and_dut,out_or_ref,out_or_dut,out_xor_ref,out_xor_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in );
	reference_module good1 (
		.in,
		.out_and(out_and_ref),
		.out_or(out_or_ref),
		.out_xor(out_xor_ref) );

	top_module top_module1 (
		.in,
		.out_and(out_and_dut),
		.out_or(out_or_dut),
		.out_xor(out_xor_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_out_and) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out_and", stats1.errors_out_and, stats1.errortime_out_and);
		else $display("Hint: Output '%s' has no mismatches.", "out_and");
		if (stats1.errors_out_or) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out_or", stats1.errors_out_or, stats1.errortime_out_or);
		else $display("Hint: Output '%s' has no mismatches.", "out_or");
		if (stats1.errors_out_xor) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out_xor", stats1.errors_out_xor, stats1.errortime_out_xor);
		else $display("Hint: Output '%s' has no mismatches.", "out_xor");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { out_and_ref, out_or_ref, out_xor_ref } === ( { out_and_ref, out_or_ref, out_xor_ref } ^ { out_and_dut, out_or_dut, out_xor_dut } ^ { out_and_ref, out_or_ref, out_xor_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (out_and_ref !== ( out_and_ref ^ out_and_dut ^ out_and_ref ))
		begin if (stats1.errors_out_and == 0) stats1.errortime_out_and = $time;
			stats1.errors_out_and = stats1.errors_out_and+1'b1; end
		if (out_or_ref !== ( out_or_ref ^ out_or_dut ^ out_or_ref ))
		begin if (stats1.errors_out_or == 0) stats1.errortime_out_or = $time;
			stats1.errors_out_or = stats1.errors_out_or+1'b1; end
		if (out_xor_ref !== ( out_xor_ref ^ out_xor_dut ^ out_xor_ref ))
		begin if (stats1.errors_out_xor == 0) stats1.errortime_out_xor = $time;
			stats1.errors_out_xor = stats1.errors_out_xor+1'b1; end

	end
endmodule

simple_description: This module takes in four inputs and outputs the logical AND, OR, and XOR of the inputs.

detail_description: This Verilog module named top has four inputs, in[3:0], and three outputs, out_and, out_or, and out_xor. The in[3:0] inputs are four bits wide. The out_and, out_or, and out_xor outputs are all single bits.   The module assigns the out_and output to the result of a logical AND operation on all of the bits in the in[3:0] inputs. The out_or output is assigned to the result of a logical OR operation on all of the bits in the in[3:0] inputs. The out_xor output is assigned to the result of a logical XOR operation on all of the bits in the in[3:0] inputs.   Therefore, the top module takes four bits as inputs and performs a logical AND, OR, and XOR operation on them, producing three single bit outputs.


prompt:
module top_module (
	input clk,
	input reset,
	input x,
	output reg z
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clk,
	input reset,
	input x,
	output reg z
);
	parameter A=0, B=1, C=2, D=3, E=4;
	reg [2:0] state, next;

	always @(posedge clk) begin
		if (reset) state <= A;
		else state <= next;
	end

	always_comb begin
		case (state)
			A: next = x ? B : A;
			B: next = x ? E : B;
			C: next = x ? B : C;
			D: next = x ? C : B;
			E: next = x ? E : D;
			default: next = 'x;
		endcase
	end

	assign z = (state == D) || (state == E);

endmodule

module stimulus_gen (
	input clk,
	output logic reset,
	output logic x
);

	initial begin
		reset = 1;
		x = 0;
		@(posedge clk);
		@(posedge clk);
		reset = 0;
		@(posedge clk);
		@(posedge clk);

		repeat(500) @(posedge clk, negedge clk) begin
			reset <= !($random & 63);
			x <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_z;
		int errortime_z;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic reset;
	logic x;
	logic z_ref;
	logic z_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,reset,x,z_ref,z_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.reset,
		.x );
	reference_module good1 (
		.clk,
		.reset,
		.x,
		.z(z_ref) );

	top_module top_module1 (
		.clk,
		.reset,
		.x,
		.z(z_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_z) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "z", stats1.errors_z, stats1.errortime_z);
		else $display("Hint: Output '%s' has no mismatches.", "z");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { z_ref } === ( { z_ref } ^ { z_dut } ^ { z_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (z_ref !== ( z_ref ^ z_dut ^ z_ref ))
		begin if (stats1.errors_z == 0) stats1.errortime_z = $time;
			stats1.errors_z = stats1.errors_z+1'b1; end

	end
endmodule

detail_description: The reset input initializes the state to A. The top module has a clock, a reset, an input, and an output. The input x is the current input and the output z is the output of the module. The output is high when the state is D or E. The internal state is represented by 3 bits, so there are 8 states. The case statement describes the state transition when x is high or low. If the state is A and x is low, then the next state is also A. If the state is A and x is high, then the next state is B. If the state is B and x is low, then the next state is B. If the state is B and x is high, then the next state is E. If the state is C and x is low, then the next state is C. If the state is C and x is high, then the next state is B. If the state is D and x is low, then the next state is B. If the state is D and x is high, then the next state is C. If the state is E and x is low, then the next state is D. If the state is E and x is high, then the next state is E.


prompt:
module top_module (
	input clk,
	input resetn,
	input x,
	input y,
	output f,
	output g
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clk,
	input resetn,
	input x,
	input y,
	output f,
	output g
);
	parameter A=0, B=1, S0=2, S1=3, S10=4, G1=5, G2=6, P0=7, P1=8;
	reg [3:0] state, next;

	always @(posedge clk) begin
		if (~resetn) state <= A;
		else state <= next;
	end

	always_comb begin
		case (state)
			A: next = B;
			B: next = S0;
			S0: next = x ? S1 : S0;
			S1: next = x ? S1 : S10;
			S10: next = x? G1 : S0;
			G1: next = y ? P1 : G2;
			G2: next = y ? P1 : P0;
			P0: next = P0;
			P1: next = P1;
			default: next = 'x;
		endcase
	end

	assign f = (state == B);
	assign g = (state == G1) || (state == G2) || (state == P1);
endmodule

module stimulus_gen (
	input clk,
	output logic resetn,
	output logic x, y
);

	initial begin
		resetn = 0;
		x = 0;
		y = 0;
		@(posedge clk);
		@(posedge clk);
		resetn = 1;
		repeat(500) @(posedge clk, negedge clk) begin
			resetn <= ($random & 31) != 0;
			{x,y} <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_f;
		int errortime_f;
		int errors_g;
		int errortime_g;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic resetn;
	logic x;
	logic y;
	logic f_ref;
	logic f_dut;
	logic g_ref;
	logic g_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,resetn,x,y,f_ref,f_dut,g_ref,g_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.resetn,
		.x,
		.y );
	reference_module good1 (
		.clk,
		.resetn,
		.x,
		.y,
		.f(f_ref),
		.g(g_ref) );

	top_module top_module1 (
		.clk,
		.resetn,
		.x,
		.y,
		.f(f_dut),
		.g(g_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_f) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "f", stats1.errors_f, stats1.errortime_f);
		else $display("Hint: Output '%s' has no mismatches.", "f");
		if (stats1.errors_g) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "g", stats1.errors_g, stats1.errortime_g);
		else $display("Hint: Output '%s' has no mismatches.", "g");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { f_ref, g_ref } === ( { f_ref, g_ref } ^ { f_dut, g_dut } ^ { f_ref, g_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (f_ref !== ( f_ref ^ f_dut ^ f_ref ))
		begin if (stats1.errors_f == 0) stats1.errortime_f = $time;
			stats1.errors_f = stats1.errors_f+1'b1; end
		if (g_ref !== ( g_ref ^ g_dut ^ g_ref ))
		begin if (stats1.errors_g == 0) stats1.errortime_g = $time;
			stats1.errors_g = stats1.errors_g+1'b1; end

	end
endmodule

detail_description:
FSM machine is implemented on this code.
From A state it goes to B and from B state it goes to S0.
From S0, if x is 1 then it goes to S1 and if x is 0 then it stays in S0 itself.
From S1, if x is 1 then it stays in S1 and if x is 0 then it goes to S10.
From S10, if x is 1 then it goes to G1 and if x is 0 then it goes to S0.
From G1, if y is 1 then it goes to P1 and if y is 0 then it goes to G2.
From G2, if y is 1 then it goes to P1 and if y is 0 then it goes to P0.
From P0, it stays in P0.
From P1, it stays in P1.

f is assigned to 1 when the state is B.
g is assigned to 1 when the state is G1 or G2 or P1.


prompt:
module top_module(
	input clk,
	input [7:0] d,
	input reset,
	output reg [7:0] q);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input [7:0] d,
	input reset,
	output reg [7:0] q);

	always @(negedge clk)
		if (reset)
			q <= 8'h34;
		else
			q <= d;

endmodule

module stimulus_gen (
	input clk,
	output reg [7:0] d, output reg reset,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable,
	input tb_match
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	task reset_test(input async=0);
		bit arfail, srfail, datafail;

		@(posedge clk);
		@(posedge clk) reset <= 0;
		repeat(3) @(posedge clk);

		@(negedge clk) begin datafail = !tb_match ; reset <= 1; end
		@(posedge clk) arfail = !tb_match;
		@(posedge clk) begin
			srfail = !tb_match;
			reset <= 0;
		end
		if (srfail)
			$display("Hint: Your reset doesn't seem to be working.");
		else if (arfail && (async || !datafail))
			$display("Hint: Your reset should be %0s, but doesn't appear to be.", async ? "asynchronous" : "synchronous");
		// Don't warn about synchronous reset if the half-cycle before is already wrong. It's more likely
		// a functionality error than the reset being implemented asynchronously.

	endtask

	initial begin
		reset <= 1;
		d <= $random;
		@(negedge clk);
		@(negedge clk);
		wavedrom_start("Synchronous active-high reset");
		reset_test();
		repeat(10) @(negedge clk)
			d <= $random;
		wavedrom_stop();

		repeat(400) @(posedge clk, negedge clk) begin
			reset <= !($random & 15);
			d <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [7:0] d;
	logic reset;
	logic [7:0] q_ref;
	logic [7:0] q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,d,reset,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.d,
		.reset );
	reference_module good1 (
		.clk,
		.d,
		.reset,
		.q(q_ref) );

	top_module top_module1 (
		.clk,
		.d,
		.reset,
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { q_ref } === ( { q_ref } ^ { q_dut } ^ { q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

simple_description: This module is a synchronous reset register that assigns the value 0x34 to the output q when reset is asserted and assigns the value of the input d to q when reset is deasserted.

detail_description: This Verilog module is a simple 8-bit register. It has four ports: clk, d, reset, and q. The clk port is an input that is used to clock the register. The d port is an 8-bit input that is used to store the data in the register. The reset port is an input that is used to reset the register to a predefined value. The q port is an 8-bit output that is used to output the data stored in the register.  The module has an always block that is triggered on the negative edge of the clk signal. Inside this block, there is an if statement that checks the reset signal. If the reset signal is asserted, the q port is set to 8'h34. If the reset signal is not asserted, the q port is set to the value of the d port. This allows the register to store the data from the d port.


task_id: reduction

prompt:
module top_module (
	input [7:0] in,
	output parity
);

canonical_solution:
	assign parity = ^in;

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input [7:0] in,
	output parity
);

	assign parity = ^in;

endmodule

module stimulus_gen (
	input clk,
	output logic [7:0] in
);

	initial begin
		repeat(100) @(posedge clk, negedge clk)
			in <= $random;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_parity;
		int errortime_parity;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [7:0] in;
	logic parity_ref;
	logic parity_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,in,parity_ref,parity_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in );
	reference_module good1 (
		.in,
		.parity(parity_ref) );

	top_module top_module1 (
		.in,
		.parity(parity_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_parity) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "parity", stats1.errors_parity, stats1.errortime_parity);
		else $display("Hint: Output '%s' has no mismatches.", "parity");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { parity_ref } === ( { parity_ref } ^ { parity_dut } ^ { parity_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (parity_ref !== ( parity_ref ^ parity_dut ^ parity_ref ))
		begin if (stats1.errors_parity == 0) stats1.errortime_parity = $time;
			stats1.errors_parity = stats1.errors_parity+1'b1; end

	end
endmodule

simple_description: This module takes in an 8-bit input and outputs the parity bit of the input.

detail_description: This Verilog module is a simple parity checker. It has one 8-bit input port, "in", and one output port, "parity". The output port is assigned to the bitwise XOR of the 8-bit input port. This means that the output will be a single bit that is 1 if the number of 1s in the 8-bit input is odd, and 0 if the number of 1s in the 8-bit input is even. This module can be used to detect errors in 8-bit data.


prompt:
module top_module (
	input in,
	input [1:0] state,
	output reg [1:0] next_state,
	output out
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input in,
	input [1:0] state,
	output reg [1:0] next_state,
	output out
);
	parameter A=0, B=1, C=2, D=3;

    always_comb begin
		case (state)
			A: next_state = in ? B : A;
			B: next_state = in ? B : C;
			C: next_state = in ? D : A;
			D: next_state = in ? B : C;
		endcase
    end

	assign out = (state==D);

endmodule

module stimulus_gen (
	input clk,
	output logic in,
	output logic [1:0] state
);

	initial begin
		repeat(100) @(posedge clk, negedge clk) begin
			in <= $random;
			state <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_next_state;
		int errortime_next_state;
		int errors_out;
		int errortime_out;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic in;
	logic [1:0] state;
	logic [1:0] next_state_ref;
	logic [1:0] next_state_dut;
	logic out_ref;
	logic out_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,in,state,next_state_ref,next_state_dut,out_ref,out_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in,
		.state );
	reference_module good1 (
		.in,
		.state,
		.next_state(next_state_ref),
		.out(out_ref) );

	top_module top_module1 (
		.in,
		.state,
		.next_state(next_state_dut),
		.out(out_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_next_state) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "next_state", stats1.errors_next_state, stats1.errortime_next_state);
		else $display("Hint: Output '%s' has no mismatches.", "next_state");
		if (stats1.errors_out) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "out", stats1.errors_out, stats1.errortime_out);
		else $display("Hint: Output '%s' has no mismatches.", "out");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { next_state_ref, out_ref } === ( { next_state_ref, out_ref } ^ { next_state_dut, out_dut } ^ { next_state_ref, out_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (next_state_ref !== ( next_state_ref ^ next_state_dut ^ next_state_ref ))
		begin if (stats1.errors_next_state == 0) stats1.errortime_next_state = $time;
			stats1.errors_next_state = stats1.errors_next_state+1'b1; end
		if (out_ref !== ( out_ref ^ out_dut ^ out_ref ))
		begin if (stats1.errors_out == 0) stats1.errortime_out = $time;
			stats1.errors_out = stats1.errors_out+1'b1; end

	end
endmodule

simple_description: The top Verilog module implements a state machine that transitions between states A, B, C, and D based on the input and outputs a signal when it is in state D.

detail_description: This Verilog module is a state machine that has four states, A, B, C, and D. The input port 'in' is a single bit signal that is used to control the state transitions. The 'state' port is a two bit signal that is used to represent the current state of the state machine. The 'next_state' port is a two bit signal that is used to represent the next state of the state machine. The 'out' port is a single bit signal that is used to indicate when the state machine is in state D.   The always_comb block is used to define the state transitions. It uses a case statement to determine the next state of the state machine based on the current state and the value of the 'in' signal. If the current state is A and the 'in' signal is high, the next state is B. If the 'in' signal is low, the next state remains A. Similarly, if the current state is B and the 'in' signal is high, the next state is B. If the 'in' signal is low, the next state is C. If the current state is C and the 'in' signal is high, the next state is D. If the 'in' signal is low, the next state is A. Finally, if the current state is D and the 'in' signal is high, the next state is B. If the 'in' signal is low, the next state is C.   The 'out' signal is assigned to be high when the state machine is in state D. This allows the user to detect when the state machine is in state D.


prompt:
module top_module(
	input x,
	input y,
	output z);

canonical_solution:
	assign z = ~(x^y);

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input x,
	input y,
	output z);

	assign z = ~(x^y);

endmodule

module stimulus_gen (
	input clk,
	output logic x,
	output logic y,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		{x,y} <= 0;
		@(negedge clk) wavedrom_start();
			@(posedge clk) {y,x} <= 0;
			@(posedge clk) {y,x} <= 1;
			@(posedge clk) {y,x} <= 2;
			@(posedge clk) {y,x} <= 3;
		@(negedge clk) wavedrom_stop();
		repeat(100) @(posedge clk, negedge clk)
			{x, y} <= $random % 4;
		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_z;
		int errortime_z;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic x;
	logic y;
	logic z_ref;
	logic z_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,x,y,z_ref,z_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.x,
		.y );
	reference_module good1 (
		.x,
		.y,
		.z(z_ref) );

	top_module top_module1 (
		.x,
		.y,
		.z(z_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_z) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "z", stats1.errors_z, stats1.errortime_z);
		else $display("Hint: Output '%s' has no mismatches.", "z");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { z_ref } === ( { z_ref } ^ { z_dut } ^ { z_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (z_ref !== ( z_ref ^ z_dut ^ z_ref ))
		begin if (stats1.errors_z == 0) stats1.errortime_z = $time;
			stats1.errors_z = stats1.errors_z+1'b1; end

	end
endmodule

simple_description: This module assigns the output z to the logical negation of the XOR of inputs x and y.

detail_description: This Verilog module is a simple logic gate that takes two inputs, x and y, and produces an output, z. The output is the logical negation of the exclusive-or (XOR) of the two inputs. In other words, the output is true if either x or y is true, but not both. If both x and y are true, then the output is false. This module is a basic building block for more complex digital logic circuits.


prompt:
module top_module (
	input clk,
	input reset,
	input w,
	output z
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clk,
	input reset,
	input w,
	output z
);
	parameter A=0,B=1,C=2,D=3,E=4,F=5;
	reg[2:0] state, next;

	always @(posedge clk)
		if (reset) state <= A;
		else state <= next;

	always_comb begin
		case (state)
			A: next = w ? B : A;
			B: next = w ? C : D;
			C: next = w ? E : D;
			D: next = w ? F : A;
			E: next = w ? E : D;
			F: next = w ? C : D;
			default: next = 'x;
		endcase
	end

	assign z = (state == E) || (state == F);

endmodule

module stimulus_gen (
	input clk,
	output logic reset,
	output logic w
);

	initial begin
		repeat(200) @(posedge clk, negedge clk) begin
			reset <= ($random & 'h1f) == 0;
			w <= $random;
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_z;
		int errortime_z;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic reset;
	logic w;
	logic z_ref;
	logic z_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,reset,w,z_ref,z_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.reset,
		.w );
	reference_module good1 (
		.clk,
		.reset,
		.w,
		.z(z_ref) );

	top_module top_module1 (
		.clk,
		.reset,
		.w,
		.z(z_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_z) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "z", stats1.errors_z, stats1.errortime_z);
		else $display("Hint: Output '%s' has no mismatches.", "z");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { z_ref } === ( { z_ref } ^ { z_dut } ^ { z_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (z_ref !== ( z_ref ^ z_dut ^ z_ref ))
		begin if (stats1.errors_z == 0) stats1.errortime_z = $time;
			stats1.errors_z = stats1.errors_z+1'b1; end

	end
endmodule

simple_description: This module implements a finite state machine with 6 states and a single output z which is true when the state is either E or F.

detail_description: The top module is a state machine that has three inputs (clk, reset, and w) and one output (z). The clk input is a clock signal that is used to synchronize the state transitions. The reset input is a synchronous reset signal that is used to reset the state machine to its initial state. The w input is an input signal that is used to control the state transitions. The z output is an output signal that is set to 1 when the state machine is in either state E or F.  The state machine has six states, A, B, C, D, E, and F, which are represented by a 3-bit register called state. The state transitions are determined by the w input and the current state. The next state is determined by a combinational logic block that is implemented using a case statement. If the w input is 0, the state transitions from A to A, from B to D, from C to D, from D to A, from E to D, and from F to D. If the w input is 1, the state transitions from A to B, from B to C, from C to E, from D to F, from E to E, and from F to C.  The output z is set to 1 when the state machine is in either state E or F. This is implemented by an assign statement that sets the z output to 1 when the state register is equal to either E or F.


prompt:
module top_module(
	input clk,
	input resetn,
	input [1:0] byteena,
	input [15:0] d,
	output reg [15:0] q);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input resetn,
	input [1:0] byteena,
	input [15:0] d,
	output reg [15:0] q);

	always @(posedge clk) begin
		if (!resetn)
			q <= 0;
		else begin
			if (byteena[0])
				q[7:0] <= d[7:0];
			if (byteena[1])
				q[15:8] <= d[15:8];
		end
	end

endmodule

module stimulus_gen (
	input clk,
	output reg [15:0] d, output reg [1:0] byteena,
	output reg resetn,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable,
	input tb_match
);
	reg reset;
	assign resetn = ~reset;

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	task reset_test(input async=0);
		bit arfail, srfail, datafail;

		@(posedge clk);
		@(posedge clk) reset <= 0;
		repeat(3) @(posedge clk);

		@(negedge clk) begin datafail = !tb_match ; reset <= 1; end
		@(posedge clk) arfail = !tb_match;
		@(posedge clk) begin
			srfail = !tb_match;
			reset <= 0;
		end
		if (srfail)
			$display("Hint: Your reset doesn't seem to be working.");
		else if (arfail && (async || !datafail))
			$display("Hint: Your reset should be %0s, but doesn't appear to be.", async ? "asynchronous" : "synchronous");
		// Don't warn about synchronous reset if the half-cycle before is already wrong. It's more likely
		// a functionality error than the reset being implemented asynchronously.

	endtask

	initial begin
		reset <= 1;
		byteena <= 2'b11;
		d <= 16'habcd;
		@(posedge clk);
		wavedrom_start("Synchronous active-low reset");
		reset_test(0);
		repeat(2) @(posedge clk);
		wavedrom_stop();
		@(posedge clk);

		byteena <= 2'b11;
		d <= $random;
		@(posedge clk);
		@(negedge clk);
		wavedrom_start("DFF with byte enables");
		repeat(10) @(posedge clk) begin
			d <= $random;
			byteena <= byteena + 1;
		end
		wavedrom_stop();

		repeat(400) @(posedge clk, negedge clk) begin
			byteena[0] <= ($random & 3) != 0;
			byteena[1] <= ($random & 3) != 0;
			d <= $random;
		end
		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic resetn;
	logic [1:0] byteena;
	logic [15:0] d;
	logic [15:0] q_ref;
	logic [15:0] q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,resetn,byteena,d,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.resetn,
		.byteena,
		.d );
	reference_module good1 (
		.clk,
		.resetn,
		.byteena,
		.d,
		.q(q_ref) );

	top_module top_module1 (
		.clk,
		.resetn,
		.byteena,
		.d,
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { q_ref } === ( { q_ref } ^ { q_dut } ^ { q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

simple_description: This module is a synchronous register that loads data into the output q based on the byteena and d inputs when the clock signal is high.

detail_description: This Verilog module is a top-level module which is used to write data to a 16-bit register. It has five inputs and one output. The inputs are a clock signal (clk), a reset signal (resetn), a 2-bit byte enable signal (byteena), and a 16-bit data signal (d). The output is a 16-bit register (q).  The module is triggered by a rising edge of the clock signal. When the reset signal is low, the register is reset to 0. Otherwise, the data signal is written to the register based on the byte enable signal. If the first bit of the byte enable signal is high, the lower 8 bits of the data signal are written to the lower 8 bits of the register. If the second bit of the byte enable signal is high, the upper 8 bits of the data signal are written to the upper 8 bits of the register.


task_id: edgedetect

prompt:
module top_module(
	input clk,
	input [7:0] in,
	output reg [7:0] pedge);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input [7:0] in,
	output reg [7:0] pedge);

	reg [7:0] d_last;

	always @(posedge clk) begin
		d_last <= in;
		pedge <= in & ~d_last;
	end

endmodule

module stimulus_gen (
	input clk,
	input tb_match,
	output reg [7:0] in,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		in <= 0;
		@(posedge clk);
		wavedrom_start("");
		repeat(2) @(posedge clk);
		in <= 1;
		repeat(4) @(posedge clk);
		in <= 0;
		repeat(4) @(negedge clk);
		in <= 6;
		repeat(2) @(negedge clk);
		in <= 0;
		repeat(2) @(posedge clk);
		wavedrom_stop();

		repeat(200)
			@(posedge clk, negedge clk) in <= $random;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_pedge;
		int errortime_pedge;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [7:0] in;
	logic [7:0] pedge_ref;
	logic [7:0] pedge_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,in,pedge_ref,pedge_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.in );
	reference_module good1 (
		.clk,
		.in,
		.pedge(pedge_ref) );

	top_module top_module1 (
		.clk,
		.in,
		.pedge(pedge_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_pedge) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "pedge", stats1.errors_pedge, stats1.errortime_pedge);
		else $display("Hint: Output '%s' has no mismatches.", "pedge");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { pedge_ref } === ( { pedge_ref } ^ { pedge_dut } ^ { pedge_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (pedge_ref !== ( pedge_ref ^ pedge_dut ^ pedge_ref ))
		begin if (stats1.errors_pedge == 0) stats1.errortime_pedge = $time;
			stats1.errors_pedge = stats1.errors_pedge+1'b1; end

	end
endmodule

simple_description: This module detects the rising edge of the input signal and outputs it on the pedge output.

detail_description: This top Verilog module is used to detect the rising edges of an 8-bit input signal. The module has three ports, a clock input, an 8-bit input signal, and an 8-bit output signal.   The clock input is used to synchronize the module's operations. The 8-bit input signal is used to detect the rising edges. The 8-bit output signal is used to indicate the rising edges.   The module contains a register, d_last, which is used to store the value of the input signal from the previous clock cycle.   The module is always triggered on the rising edge of the clock signal. When triggered, the module stores the current value of the 8-bit input signal in the d_last register. It then calculates the 8-bit output signal, pedge, by performing a bitwise AND operation between the current value of the 8-bit input signal and the inverse of the value stored in the d_last register. This results in a signal that is high only when a rising edge is detected.


prompt:
module top_module (
	input clock,
	input a,
	output reg p,
	output reg q
);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module (
	input clock,
	input a,
	output reg p,
	output reg q
);

	always @(negedge clock)
		q <= a;

	always @(*)
		if (clock)
			p = a;
endmodule

module stimulus_gen (
	input clk,
	output logic clock=0,
	output logic a,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

	always begin
		repeat(3) @(posedge clk);
		clock = ~clock;
	end

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		a <= 0;
		@(negedge clock) {a} <= 0;
		@(negedge clk) wavedrom_start("Unknown circuit");
			@(posedge clk) {a} <= 0;
			repeat(14) @(posedge clk,negedge clk) a <= ~a;
			repeat(5) @(posedge clk, negedge clk);
			repeat(8) @(posedge clk,negedge clk) a <= ~a;
		wavedrom_stop();

		repeat(200) @(posedge clk, negedge clk)
			a <= $urandom;
		$finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_p;
		int errortime_p;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic clock;
	logic a;
	logic p_ref;
	logic p_dut;
	logic q_ref;
	logic q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clock,a,p_ref,p_dut,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.clock,
		.a );
	reference_module good1 (
		.clock,
		.a,
		.p(p_ref),
		.q(q_ref) );

	top_module top_module1 (
		.clock,
		.a,
		.p(p_dut),
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_p) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "p", stats1.errors_p, stats1.errortime_p);
		else $display("Hint: Output '%s' has no mismatches.", "p");
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { p_ref, q_ref } === ( { p_ref, q_ref } ^ { p_dut, q_dut } ^ { p_ref, q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (p_ref !== ( p_ref ^ p_dut ^ p_ref ))
		begin if (stats1.errors_p == 0) stats1.errortime_p = $time;
			stats1.errors_p = stats1.errors_p+1'b1; end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

detail_description: This Verilog module has 2 inputs and 2 outputs. The inputs are a clock (clock) and a signal (a). The outputs are two registers, p and q. The clock signal is used to trigger the two always blocks. The first always block is triggered on the negative edge of the clock signal. This always block assigns the current value of the signal a to the register q. The second always block is triggered on any change of the input signal a. This always block assigns the current value of the signal a to the register p if the clock signal is high.


prompt:
module top_module(
	input clk,
	input load,
	input [511:0] data,
	output reg [511:0] q);

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
module reference_module(
	input clk,
	input load,
	input [511:0] data,
	output reg [511:0] q);

	always @(posedge clk) begin
		if (load)
			q <= data;
		else begin
			q <= q[$bits(q)-1:1] ^ {q[$bits(q)-2:0], 1'b0} ;
		end
	end
endmodule

module stimulus_gen (
	input clk,
	output reg load,
	output reg[511:0] data,
	output reg[511:0] wavedrom_title,
	output reg wavedrom_enable
);

// Add two ports to module stimulus_gen:
//    output [511:0] wavedrom_title
//    output reg wavedrom_enable

	task wavedrom_start(input[511:0] title = "");
	endtask

	task wavedrom_stop;
		#1;
	endtask

	initial begin
		data <= 0;
		data[0] <= 1'b1;
		load <= 1;
		@(posedge clk); wavedrom_start("Sierpiński triangle: See Hint.");
		@(posedge clk);
		@(posedge clk);
		load <= 0;
		repeat(10) @(posedge clk);
		wavedrom_stop();

		data <= 0;
		data[256] <= 1'b1;
		load <= 1;
		@(posedge clk);
		@(posedge clk);
		@(posedge clk);
		load <= 0;
		repeat(1000) @(posedge clk) begin
		end
		data <= 512'h1000000000000001;
		load <= 1;
		@(posedge clk);
		load <= 0;
		repeat(1000) @(posedge clk) begin
		end

		data <= $random;
		load <= 1;
		@(posedge clk);
		load <= 0;
		repeat(1000) @(posedge clk) begin
		end

		data <= 0;
		load <= 1;
		repeat(20) @(posedge clk);
		repeat(2) @(posedge clk) data <= data + 2;
		@(posedge clk) begin
			load <= 0;
			data <= data + 1;
		end
		repeat(20) @(posedge clk) data <= data + 1;
		repeat(500) @(posedge clk) begin
		end

		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_q;
		int errortime_q;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic load;
	logic [511:0] data;
	logic [511:0] q_ref;
	logic [511:0] q_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,clk,load,data,q_ref,q_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.load,
		.data );
	reference_module good1 (
		.clk,
		.load,
		.data,
		.q(q_ref) );

	top_module top_module1 (
		.clk,
		.load,
		.data,
		.q(q_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_q) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "q", stats1.errors_q, stats1.errortime_q);
		else $display("Hint: Output '%s' has no mismatches.", "q");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { q_ref } === ( { q_ref } ^ { q_dut } ^ { q_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (q_ref !== ( q_ref ^ q_dut ^ q_ref ))
		begin if (stats1.errors_q == 0) stats1.errortime_q = $time;
			stats1.errors_q = stats1.errors_q+1'b1; end

	end
endmodule

detail_description:
The top module is a data load module. When load is 1, it will load the data in the input data to the output q, and when load is 0, it will shift the output q to the right and adding a 0 at the end.

input

input clk
input load
input [511:0] data

output

output reg [511:0] q

The output q is 512 bits long and is a reg type which can store the value inside.

Declaration

always @(posedge clk) begin

When the clock edge comes, the following operation will be executed.

The operation when load is 1

if (load)
	q <= data;
The input data will be loaded to the output q.

The operation when load is 0

else begin
	q <= q[$bits(q)-1:1] ^ {q[$bits(q)-2:0], 1'b0} ;
end
The last two bits of q are xored, and a 0 is added at the beginning of q.

End the operation

end


prompt:
module top_module(
	input [1:0] A,
	input [1:0] B,
	output z);

canonical_solution:
	assign z = A[1:0]==B[1:0];

endmodule

test:
`timescale 1 ps/1 ps
`define OK 12
`define INCORRECT 13
/*
	Midterm 2015 Question 1k. 2-bit equality comparator.
*/
module reference_module(
	input [1:0] A,
	input [1:0] B,
	output z);

	assign z = A[1:0]==B[1:0];

endmodule

module stimulus_gen (
	input clk,
	output logic [1:0] A,
	output logic [1:0] B
);

	always @(posedge clk, negedge clk)
		{A, B} <= $random % 16;

	initial begin
		repeat(1000) @(negedge clk);
		#1 $finish;
	end

endmodule

module tb();

	typedef struct packed {
		int errors;
		int errortime;
		int errors_z;
		int errortime_z;

		int clocks;
	} stats;

	stats stats1;

	wire[511:0] wavedrom_title;
	wire wavedrom_enable;
	int wavedrom_hide_after_time;

	reg clk=0;
	initial forever
		#5 clk = ~clk;

	logic [1:0] A;
	logic [1:0] B;
	logic z_ref;
	logic z_dut;

	initial begin
		$dumpfile("wave.vcd");
		$dumpvars(1, stim1.clk, tb_mismatch ,A,B,z_ref,z_dut );
	end

	wire tb_match;		// Verification
	wire tb_mismatch = ~tb_match;

	stimulus_gen stim1 (
		.clk,
		.* ,
		.A,
		.B );
	reference_module good1 (
		.A,
		.B,
		.z(z_ref) );

	top_module top_module1 (
		.A,
		.B,
		.z(z_dut) );

	bit strobe = 0;
	task wait_for_end_of_timestep;
		repeat(5) begin
			strobe <= !strobe;  // Try to delay until the very end of the time step.
			@(strobe);
		end
	endtask

	final begin
		if (stats1.errors_z) $display("Hint: Output '%s' has %0d mismatches. First mismatch occurred at time %0d.", "z", stats1.errors_z, stats1.errortime_z);
		else $display("Hint: Output '%s' has no mismatches.", "z");

		$display("Hint: Total mismatched samples is %1d out of %1d samples\n", stats1.errors, stats1.clocks);
		$display("Simulation finished at %0d ps", $time);
		$display("Mismatches: %1d in %1d samples", stats1.errors, stats1.clocks);
	end

	// Verification: XORs on the right makes any X in good_vector match anything, but X in dut_vector will only match X.
	assign tb_match = ( { z_ref } === ( { z_ref } ^ { z_dut } ^ { z_ref } ) );
	// Use explicit sensitivity list here. @(*) causes NetProc::nex_input() to be called when trying to compute
	// the sensitivity list of the @(strobe) process, which isn't implemented.
	always @(posedge clk, negedge clk) begin

		stats1.clocks++;
		if (!tb_match) begin
			if (stats1.errors == 0) stats1.errortime = $time;
			stats1.errors++;
		end
		if (z_ref !== ( z_ref ^ z_dut ^ z_ref ))
		begin if (stats1.errors_z == 0) stats1.errortime_z = $time;
			stats1.errors_z = stats1.errors_z+1'b1; end

	end
endmodule

simple_description: The top module compares two 2-bit inputs A and B and assigns the result to the output z.

detail_description: This Verilog module is a simple comparison module. It takes two 2-bit inputs, A and B, and compares them bit-by-bit. If all the bits of A are equal to the corresponding bits of B, then the output z is set to 1. Otherwise, z is set to 0. The module does not have any internal logic or state transitions, as it is simply a comparison of two inputs. The port connections of the module are as follows: A and B are both 2-bit inputs, and z is a single-bit output.