lock.vhd

1、 南北和东西方向各有一组绿、黄、红灯

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

entity lock is
	port(
				clk  : in std_logic;
				kin	 : in std_logic;
				kout : out std_logic);
end lock;

architecture a of lock is
begin
	process(clk)										
		variable i1 : std_logic;
		variable i2 : std_logic;
	begin
		if(clk'event and clk='1') then
			i1 := i2;
			i2 := kin;
			if (i1=i2) then
				kout <= i2;
			end if;
		end if;	
	end process;
end;