按键信号的边沿检测

//边沿检测
//tips：寄存了3个周期再判断
//因为按键是异步信号，先同步处理后再判断
module    edge_check(

    input    wire            clk,
    input    wire            wave,           //代表按键按下
    
    output    wire            flag_pos,
    output    wire            flag_neg

);

    reg        [3:0]            bur_wave;  //
    
    always@(posedge    clk)
        begin
            
        bur_wave <= {bur_wave[2:0] , wave};  //
        //[3] [2] [1] [0]    把下行给上行，异步信号同步处理
        //[2] [1] [0] [wave]
        
        end

    assign    flag_pos = (~bur_wave[3])&bur_wave[2];
    assign    flag_neg = (~bur_wave[2])&bur_wave[3];
endmodule    

`timescale        1ns/1ps
//200.1代表200ns 零  1ps
module    edge_check_tb();

        reg            clk;
        reg        wave;
    
        wire            flag_pos;
        wire            flag_neg;

edge_check    edge_check_inst(

    .clk            (clk),
    .wave            (wave),
    
    .flag_pos        (flag_pos),
    .flag_neg        (flag_neg)

);

initial    clk=1;
always    #10    clk=~clk;


initial    begin
    wave=0;
    #206;
    wave=1;
    #206;
    wave=0;
    #206;
    wave=1;
    #343;
    wave=0;
    #206;
    wave=1;
    #206;
    wave=0;
    #206;
    wave=1;
    #436;
    wave=0;
    #223;
    $stop;


end


endmodule