cnt24.vhd

用VHDL写的源代码程序

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

ENTITY cnt24 is 
	port(clk,rst : in std_logic;
		co : out std_logic;
        qout : out std_logic_vector(7 downto 0));		
END cnt24;

architecture behave of cnt24 is 
signal qh,ql : std_logic_vector(3 downto 0);
BEGIN
	process(rst,clk)
	begin
	if (rst='0') then ql<="0000"; qh<="0000"; co<='0';
	elsif (clk'event and clk='1') then
		if (ql=3) then ql<="0000";
			if (qh=2) then qh<="0000";co<='1';
		  	else qh<=qh+1;co<='0';
		  	end if;
		else ql<=ql+1;
		end if;
	end if;
	qout<=qh&ql;
	end process;
END behave;