独立按键消抖2

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//****************************************//
// 作    者:绯红姜梦     
// 日    期:2022、6、1      
// QQ      :2943115420        
// QQ交流群:689408654        
// 功    能:按键消抖     

// author  :crimson ginger dream
// date    :2022/6/1
// QQ      :2943115420
// QQ group:689408654
// function:press to deshake
//****************************************//
module shake_u(        
    input      clk   ,          
    input      rstn  ,    
    input      key   ,      
    output     shape   
);
//parameter delay=45;         //仿真使用
parameter delay=999999;     //下开发板使用
reg [20:0]t20ms;
reg [ 1:0]key_d;
reg [ 1:0]state;

always@(posedge clk)
    key_d <= {key_d[0],key};
always@(posedge clk or negedge rstn)
    begin
        if(!rstn)begin
            state <= 0;
        end else begin
            case(state)
                0: state <= (key_d == 2    ) ? 1 : 0;
                1: state <= (t20ms >= delay) ? 2 : 1;
                2: state <= (key_d == 1    ) ? 3 : 2;
                3: state <= (t20ms >= delay) ? 0 : 3;
                default:begin
                    state <= 0;
                end
            endcase
        end
    end
always@(posedge clk or negedge rstn)
    begin
        if(!rstn)begin
            t20ms <= 0;
        end else if(state==1 || state==3)begin
            t20ms <= t20ms+1;
        end else begin
            t20ms <= 0;
        end
    end
assign shape = (state==3 && t20ms>=delay) ? 1 : 0;

endmodule