12课 按键消抖

NET clk LOC=p24 | IOSTANDARD=LVCMOS33;
NET rst LOC=p93 | IOSTANDARD=LVCMOS33;
NET key LOC=p94 | IOSTANDARD=LVCMOS33;
NET led[0] LOC=p92 | IOSTANDARD=LVCMOS33;
NET led[1] LOC=p87 | IOSTANDARD=LVCMOS33;
NET led[2] LOC=p55 | IOSTANDARD=LVCMOS33;
NET led[3] LOC=p59 | IOSTANDARD=LVCMOS33;

module key_test(
    input    wire    clk,
    input    wire    rst,
    input    wire    key,
    output    wire    [3:0]led);
reg [3:0]    led_shift= 4'b0001;
reg            key_reg;
always @(posedge clk or negedge rst) begin
    if (rst==0) begin
        key_reg<=1;
    end
    else 
        key_reg<=key;
    
end


always @(posedge clk or negedge rst) begin
    if (rst==0) begin
        led_shift<=4'b0001;
    end
    else if (key==0&&key_reg==1) begin
        led_shift<={led_shift[2:0],led_shift[3]};
    end
end

assign led = led_shift;
endmodule

 需要过滤掉前抖动 后抖动 　　抖动5~10ms左右

计数到5ms左右产生一个按键的标志拉高 　　后抖动时将其拉低

module    debounce(
    input    wire    clk,
    input    wire    rst,
    input    wire    key,
    output    wire    op_key);

parameter cnt_end=250_000;
reg [31:0]cnt;
reg    cnt_flag;
reg key_flag;
always @(posedge clk or posedge rst) begin
    if (rst==1) begin
        cnt<=0;
    end
    else if (key==0) begin
        cnt<=cnt+1;
    end
    else begin
        cnt<=0;
    end
end

always @(posedge clk or posedge rst) begin
    if (rst==1) begin
        cnt_flag<=0;
    end
    else if(key==1) begin
        cnt_flag<=0;
    end
    else if (cnt==cnt_end) begin
        cnt_flag<=1;
    end
end

always @(posedge clk or posedge rst) begin
    if (rst==1) begin
        key_flag<=0;
    end
    else if (cnt_flag==1&&cnt==cnt_end) begin
        key_flag<=1;
    end
    else begin
        key_flag<=0;
    end
end

assign op_key =key_flag ;
endmodule