lights.vhd

1．初始状态为4个方向的红灯全亮

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;

ENTITY lights is
	port(
		  input: IN STD_LOGIC_VECTOR( 5 DOWNTO 0);
          EWR, EWY, EWG: OUT STD_LOGIC;
          SNR, SNY, SNG: OUT STD_LOGIC;
          CLK: IN STD_LOGIC
        );
END lights;

ARCHITECTURE lights_arch OF lights IS
BEGIN
  PROCESS( CLK )
BEGIN
      if( input = "000000" ) then
        EWR <= '1';   EWY <= '0';    EWG <= '0'; 
        SNR <= '1';   SNY <= '0';    SNG <= '0'; 
      elsif( input = "100100" ) then
        EWR <= '1';   EWY <= '0';    EWG <= '0'; 
        SNR <= '1';   SNY <= '0';    SNG <= '0';
      ELSIF( input = "001100" ) THEN
        EWR <= '0';   EWY <= '0';    EWG <= '1'; 
        SNR <= '1';   SNY <= '0';    SNG <= '0';
      ELSIF( input = "010100" ) THEN
        EWR <= '0';   EWY <= CLK;    EWG <= '0'; 
        SNR <= '1';   SNY <= '0';    SNG <= '0';
      ELSIF( input= "100001" ) THEN
        EWR <= '1';   EWY <= '0';    EWG <= '0'; 
        SNR <= '0';   SNY <= '0';    SNG <= '1';
      ELSIF( input = "100010" ) THEN
        EWR <= '1';   EWY <= '0';    EWG <= '0'; 
        SNR <= '0';   SNY <= CLK;    SNG <= '0';
    END IF;
END PROCESS;
END lights_arch;