题解 | #交通灯#

无法通过牛客网的测试，代码和仿真波形如下：

module triffic_light
    (
		input rst_n, //异位复位信号，低电平有效
        input clk, //时钟信号
        input pass_request,
		output wire[7:0]clock,
        output reg red,
		output reg yellow,
		output reg green
    );
reg [7:0] count,out,new;
reg [1:0] state;
reg temp_g,temp_r,temp_y,temp_g1,temp_r1,temp_y1;
parameter s0=0,s1=1,s2=2;
always @(posedge clk or negedge rst_n)
begin
if(!rst_n)
begin
count<=10;
end
else
begin
if (pass_request!=1)
begin
count<=10;
end
else
begin
count<= count==1? new : count-1;
end
end
end

always @ (*)
begin
if (!rst_n)
begin
state =s1;
temp_g=0;temp_r=1;temp_y=0;
end
else if (count==1)
begin
case (state)
s0 :begin state=s1;new=10;temp_g=0;temp_r=1;temp_y=0; end
s1 :begin state=s2;new=60;temp_g=1;temp_r=0;temp_y=0; end
s2 :begin state=s0;new=5;temp_g=0;temp_r=0;temp_y=1; end
endcase
end
end
always@(posedge clk or negedge rst_n)
begin
temp_r1<=temp_r;
temp_g1<=temp_g;
temp_y1<=temp_y;
end



always @(posedge clk or negedge rst_n)
begin
if(!rst_n)
begin
red=0;
yellow=0;
green=0;
out=10;
end
else
begin
red<=temp_r1;
green<=temp_g1;
yellow<=temp_y1;
out<=count;
end
end

assign  clock =out;

endmodule

`timescale 1ns/1ns
module textbench();
reg clk,rst_n;
	reg pass_request;
	wire red,yellow,green;
	wire [7:0]out;
 triffic_light u0
    (
		. rst_n(rst_n), //异位复位信号，低电平有效
        .clk(clk), //时钟信号
        .pass_request(pass_request),
		.clock(out),
        .red(red),
		.yellow(yellow),
		.green(green)
    );
always #5 clk=~clk;
 initial begin
        clk=0;rst_n = 0; pass_request=1;
        #10 rst_n=1;
        #150 pass_request=0;
          #10 pass_request=1;
        #2000;
$finish;
end

endmodule

仿真结果如下：