scan.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 scan IS
   PORT( 
         CLK : IN STD_LOGIC;
         Hinput : IN STD_LOGIC_VECTOR( 6 DOWNTO 0);
         Linput : IN STD_LOGIC_VECTOR( 6 DOWNTO 0);
         Zoput : OUT STD_LOGIC_VECTOR( 6 DOWNTO 0);
         Hoput : OUT STD_LOGIC;
         LOPUT : OUT STD_LOGIC
       );
END scan;

ARCHITECTURE scan_arch OF scan is
SIGNAL count : UNSIGNED( 1 DOWNTO 0);

BEGIN
	PROCESS(CLK)
    BEGIN 
      IF( CLK'event and CLK = '1' ) THEN 
        count <= count + 1;
      
        IF( COUNT = 0 ) THEN
           Hoput <= '1'; Loput <= '0'; Zoput <= Hinput;
        ELSIF( COUNT = 1 ) THEN 
           Hoput <= '0'; Loput <= '1'; Zoput <= Linput;
           COUNT <= "00";
        END IF;
     END IF;
END PROCESS;
END scan_arch;