独立按键消抖FPGA模块

module keyxiaodou (
    input clk,//the freq or clk is 50M
    input rst,//use key3 for rst button
    input key1,key2,//use key1 to light led,use key2 to turn off led
    output led);
    //--------------------------------------------------
    reg [1:0] key_r;//the first time check the key
    always @ (posedge clk or negedge rst)
        if (!rst) key_r <= 2'b11;
        else    key_r <= {key2,key1};
    
    reg [1:0] key_rb;
    always @ (posedge clk or negedge rst)
        if (!rst) key_rb <= 2'b11;
        else    key_rb <= key_r;
    
    wire [1:0] key_an = key_rb & (~key_r);//if the key[?] is pressed,key_an[?] become 1'b1
    //--------------------------------------------------
    reg [19:0] cnt;//divice the freq 1/50m*2^20=20ms
    always @ (posedge clk or negedge rst)
        if (!rst) cnt <= 20'd0;
        else if (key_an) cnt <= 20'd0;
        else    cnt <= cnt+1'b1;
    //--------------------------------------------------
    reg [1:0] keyn_r;//the second time check the key
    always @ (posedge clk or negedge rst)
        if (!rst) keyn_r <= 2'b11;
        else if(cnt ==20'hfffff) keyn_r <= {key2,key1};//relay 20ms for debounce
    
    reg [1:0] keyn_rb;
    always @ (posedge clk or negedge rst)
        if (!rst) keyn_rb <= 2'b11;
        else    keyn_rb <= keyn_r;
    
    wire [1:0] key_p = keyn_rb & (~keyn_r);
    //--------------------------------------------------
   reg led_r;
    always @ (posedge clk or negedge rst)
        if (!rst) led_r <= 1'b0;
        else if (key_p[0]) led_r <= 1'b1;
        else if (key_p[1]) led_r <= 1'b0;
        
    assign led=~led_r;
endmodule