hour.vhdl

数字钟的实现

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

--  Uncomment the following lines to use the declarations that are
--  provided for instantiating Xilinx primitive components.
--library UNISIM;
--use UNISIM.VComponents.all;

entity HOUR is
    Port ( CLK,clr : in std_logic;
		 EN: in std_logic;
           HOURSHI,HOURGE : out std_logic_vector(3 downto 0));
end HOUR;

architecture Behavioral of HOUR is
begin
 process (clr,CLK)
  VARIABLE CNT1,CNT0:STD_LOGIC_VECTOR(3 DOWNTO 0); 
  begin
   if clr='0' then
       cnt1:="0000";
       cnt0:="0000"; 		 
	elsIF CLK='1' AND  CLK'event THEN
    IF EN='0' THEN
      IF CNT1="0010" AND CNT0="0011" THEN
	    CNT0:="0000";
	    CNT1:="0000";
      ELSIF CNT0<"1001" THEN 
         CNT0:=CNT0+1;
	 ELSE    
	    CNT0:="0000";
	    CNT1:=CNT1+1;
      END IF;
    END IF;
  END IF;
        HOURSHI<=CNT1;
	   HOURGE<=CNT0;
end process;
end Behavioral;