此VHDL程式中的TACT SW要如何加才能防止開關彈跳

still · 發表於 2009-1-18 22:06:27

此程式為一個每按一次TACT SW就會進行累加1的程式,並且LED亮度會每累加一次
就會增加,共8段亮度(0~7),此程式這些功能都可以了,但是會有開關彈跳的問題,
希望能有高手幫我解決此問題

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity pwm8 is Port (
CLK : in std_logic;--clock 1KHZ
RST : in std_logic;--reset
SW  : in std_logic;--switch in
SEG7 : out std_logic_vector(6 downto 0));--
end pwm8;

architecture arch of pwm8 is

signal  SWCNT : std_logic_vector(2 downto 0);
signal  PWMCNT : std_logic_vector(2 downto 0);
signal  DISP : std_logic;

begin

--toggle switch input counter
process(RST,SW)
begin
if RST='1' then
      SWCNT<="000";
elsif rising_edge(SW) then
      SWCNT<=SWCNT+'1';
end if;
end process;

--pwm counter
process(RST,CLK)
begin
if RST='1' then
      PWMCNT<="000";
      DISP<='0';
elsif rising_edge(CLK) then
      PWMCNT<=PWMCNT+'1';
      if (PWMCNT="111") then
         DISP<='1';
      elsif (PWMCNT=SWCNT) then
         DISP<='0';
      end if;
end if;
end process;

--7-segment display decoder
process(DISP,SWCNT)
variable DISPEN : std_logic_vector(3 downto 0);
begin
DISPEN := DISP SWCNT;
case DISPEN is --SEG7<="abcdefg"
      when "1000"=>SEG7<="1111110";
      when "1001"=>SEG7<="0110000";
      when "1010"=>SEG7<="1101101";
      when "1011"=>SEG7<="1111001";
      when "1100"=>SEG7<="0110011";
      when "1101"=>SEG7<="1011011";
      when "1110"=>SEG7<="1011111";
      when "1111"=>SEG7<="1110000";
      when others=>SEG7<="0000000";
end case;
end process;
end arch;

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[問題求助] 此VHDL程式中的TACT SW要如何加才能防止開關彈跳