交通信号灯

 绿灯25秒，黄灯5秒，红灯30s

`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Engineer: connor jiao
// Create Date: 10:14 2020/6/5
// Design Name: 
// Module Name: 
// Function   :  
// Revision 0.01 - File Created
// Additional Comments:
//////////////////////////////////////////////////////////////////////////////////
module traffic(
                clk,
                rst_n,
                light1,
                light2
                );
    input clk;
    input rst_n;
    output reg [2:0]light1;
    output reg [2:0]light2;
    /* parameter cnt5s=249_999_999,cnt25s=1_249_999_999; */
    parameter cnt5s=249,cnt25s=1_249;//仿真用
    localparam IDLE=5'b00001,
                S1=5'b00010,
                S2=5'b00100,
                S3=5'b01000,
                S4=5'b10000;
    reg [4:0]current_state,next_state;
    reg [31:0]cnt;
    reg en_cnt;
    //使能和计数
    always@(posedge clk or negedge rst_n)
        if(!rst_n)
            cnt<=32'd0;
        else if(en_cnt==1'b1)
            cnt<=cnt+32'd1;
        else
            cnt<=32'd0;
    //状态切换
    always@(posedge clk or negedge rst_n)
        if(!rst_n)
            current_state<=IDLE;
        else
            current_state<=next_state;
    //次态生成
    always@(*)
        if(!rst_n)begin
            en_cnt=0;
            next_state=IDLE;
        end
        else begin
            case(current_state)
                IDLE:begin
                    en_cnt=1;
                    if(cnt==cnt5s)begin
                        next_state=S1;
                        en_cnt=0;
                    end
                    else
                        next_state=IDLE;
                end
                S1:begin
                    en_cnt=1;
                    if(cnt==cnt25s)begin
                        next_state=S2;
                        en_cnt=0;
                    end
                    else
                        next_state=S1;
                end
                S2:begin
                    en_cnt=1;
                    if(cnt==cnt5s)begin
                        next_state=S3;
                        en_cnt=0;
                    end
                    else
                        next_state=S2;
                end
                S3:begin
                    en_cnt=1;
                    if(cnt==cnt25s)begin
                        next_state=S4;
                        en_cnt=0;
                    end
                    else
                        next_state=S3;
                end
                S4:begin
                    en_cnt=1;
                    if(cnt==cnt5s)begin
                        next_state=S1;
                        en_cnt=0;
                    end
                    else
                        next_state=S4;
                end
                default:begin
                
                    en_cnt=0;
                    next_state=IDLE;
                end
            endcase
        end
    //
    always@(posedge clk or negedge rst_n)
        if(!rst_n)begin
            light1<=3'b010;
            light2<=3'b010;
        end
        else begin
            case(current_state)
                IDLE:begin
                    light1<=3'b010;
                    light2<=3'b010;
                end
                S1:begin
                    light1<=3'b100;
                    light2<=3'b001;
                end
                S2:begin
                    light1<=3'b100;
                    light2<=3'b010;
                end
                S3:begin
                   light1<=3'b001;
                   light2<=3'b100; 
                end
                S4:begin
                   light1<=3'b010;
                   light2<=3'b100;
                end
                default:begin
                   light1<=3'b010;
                   light2<=3'b010;
                end
            endcase
        end
endmodule

`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Engineer: connor jiao
// Create Date: 
// Design Name: 
// Module Name: 
// Function   :  
// Revision 0.01 - File Created
// Additional Comments:
//////////////////////////////////////////////////////////////////////////////////
module traffic_tb();
    reg clk;
    reg rst_n;
    wire [2:0]light1;
    wire [2:0]light2;
    traffic traffic(
                .clk(clk),
                .rst_n(rst_n),
                .light1(light1),
                .light2(light2)
                );
    initial clk=0;
    always #10 clk=~clk;
    initial begin
        rst_n=0;
        #201;
        rst_n=1;
        
    end
endmodule