DE2 Quartus Debounced Circuitry

Hi,

Heres a (4) switch debouncer written in AHDL quite like mentioned above:

Hope it works for you - it certainly works for me.

Peter

-------------------------------------------------------------------

SUBDESIGN debounce

(

clk : INPUT;

key_pressed[3..0] : INPUT;

pulse[3..0] : OUTPUT;

)

VARIABLE

count_reg0[20..0] : DFF;

at_zero0 : NODE;

count_reg1[20..0] : DFF;

at_zero1 : NODE;

count_reg2[20..0] : DFF;

at_zero2 : NODE;

count_reg3[20..0] : DFF;

at_zero3 : NODE;

BEGIN

% Preset to 255 when key bounces or is not %

% pressed. Decrement when key is pressed. %

%-0---%

count_reg0[].clk = clk;

count_reg0[].prn = not key_pressed[0];

count_reg0[].d = count_reg0[].q - (00000,!at_zero0);

% Emit single pulse when counter reaches 1. %

pulse[0] = count_reg0[].q == h"00001";

% Don't let counter decrement below zero. %

at_zero0 = count_reg0[].q == h"00000";

%-1---%

count_reg1[].clk = clk;

count_reg1[].prn = not key_pressed[1];

count_reg1[].d = count_reg1[].q - (00000,!at_zero1);

% Emit single pulse when counter reaches 1. %

pulse[1] = count_reg1[].q == h"00001";

% Don't let counter decrement below zero. %

at_zero1 = count_reg1[].q == h"00000";

%-2---%

count_reg2[].clk = clk;

count_reg2[].prn = not key_pressed[2];

count_reg2[].d = count_reg2[].q - (00000,!at_zero2);

% Emit single pulse when counter reaches 1. %

pulse[2] = count_reg2[].q == h"00001";

% Don't let counter decrement below zero. %

at_zero2 = count_reg2[].q == h"00000";

%-3--%

count_reg3[].clk = clk;

count_reg3[].prn = not key_pressed[3];

count_reg3[].d = count_reg3[].q - (00000,!at_zero3);

% Emit single pulse when counter reaches 1. %

pulse[3] = count_reg3[].q == h"00001";

% Don't let counter decrement below zero. %

at_zero3 = count_reg3[].q == h"00000";

END;