how to implement debouncing in verilog

Question

I am using push button of DE2 board as asynchronous reset, but it fails to work. This is my module for a n-bit register:

module regne (D, Clock, Resetn, Q);

    parameter n;
    input [n-1:0] D;
    input Clock, Resetn;
    output reg [n-1:0] Q;

    always @ (posedge Clock or negedge Resetn)
    begin
        if (Resetn == 0)
            Q[n-1:0] <= 'b0;
        else
            Q[n-1:0] <= D[n-1:0];
    end
endmodule

However, the reset fails to work. It does not do anything when I press the push button. I think it is caused by bouncing of push button. So how can I implement debouncing in Verilog?

If you press and hold reset does it still not function property? If not, this is a connectivity issue and not a bounce issue. If a long press does cause a reset then check to see if the DE2 board is filtering inputs. — Greg, Nov 06 '13 at 01:42
Are you sure that the push buttons are pull downs? Your code resets when the `Resetn` line is `0`. Try triggering on `posedge Clock or posedge Resetn` and making the if statement read `if (Resetn == 1)`. — Neil Forrester, Nov 06 '13 at 01:46
I am sure that the push button on DE2 is pull down. And it does not work even if I press and hold button for a while — SHuoDo, Nov 06 '13 at 02:49
Check the pinout of the generated bit stream is correct - there are a variety of logfiles with this information in normally — Martin Thompson, Nov 06 '13 at 12:07

score 0 · Answer 1 · answered Nov 06 '13 at 15:32

You don't need to implement debouncer for DE2 buttons. Its buttons (push buttons and switch buttons) have debouncer by themselves.

Replace

always @ (posedge Clock or negedge Resetn)

with

always @ (posedge Clock)

If it didn't work and you are sure about your pin assignments, make sure your board is working correctly.

how to implement debouncing in verilog

1 Answers1