and2.vhd

数字钟的设计,实现正点报时的系统!.......

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity AND2 is port 
   (CKDSP,CR:  in std_logic;
    AD3,AD2,AD1,AD0:  out std_logic);
end;
architecture ARC_AND2 of AND2 is
   signal  dou:  std_logic_vector(3 downto 0);
   begin
      AD3<=dou(3);
      AD2<=dou(2);
      AD1<=dou(1);
      AD0<=dou(0);
process(CKDSP,CR)
   begin
   if(CR='0')then
      dou<="0000";
   elsif(CKDSP'event and CKDSP='1')then
           if(dou="1111")then
               dou<="0000";
           else
               dou<=dou+1;
           end if;
        end if;
   end process;
end ARC_AND2;