daoji10.vhd

实现抢答器功能

--倒时时为30秒
--首先是10位倒计时
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity daoji10 is
    Port ( EN,clk,rst : in std_logic;
           CQ : out std_logic_vector(3 downto 0);
           CL : out std_logic);
end daoji10;


architecture Behavioral of daoji10 is
signal CQI : std_logic_vector(3 downto 0);
begin
CQ<=CQI;
process(clk,rst)
begin
   if rst='0'then
		CQI<="1001";
   elsif CLK'EVENT AND CLK='1' then
          if EN='0' THEN
            if CQI > "0001" then
			       CQI<=CQI-1;
            elsif cqi="0001" then
			       CQI<="0000";CL <='0';
			elsif  cqi="0000" then
			       CQI<="1001";CL <='1';
           end if;
         end if;
   END IF;
   
end process;
end Behavioral;