light.vhd

这是一个用VHDL编写的发光二极管走马灯

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY light IS
PORT(clo,sw1,btn2: IN STD_LOGIC;
     ld: OUT STD_LOGIC_VECTOR(8 DOWNTO 1));
END light;
ARCHITECTURE light_arch OF light IS
SIGNAL a:STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
  PROCESS(btn2,clo,sw1)
     BEGIN
     IF(btn2='1')THEN
     ld<="00000000";
      ELSE
        IF(SW1='0')THEN
			IF(a="1111")THEN
			a<="0000";
			elsif (clo'event AND clo='1')THEN
           a<=a+1;
			
          CASE a IS
            WHEN"0000"=>ld<="10000000";
            WHEN"0001"=>ld<="01000000";
			WHEN"0010"=>ld<="00100000";
			WHEN"0011"=>ld<="00010000";
			WHEN"0100"=>ld<="00001000";
			WHEN"0101"=>ld<="00000100";
			WHEN"0110"=>ld<="00000010";
			WHEN"0111"=>ld<="00000001";
			WHEN"1000"=>ld<="00000010";
			WHEN"1001"=>ld<="00000100";
			WHEN"1010"=>ld<="00001000";
			WHEN"1011"=>ld<="00010000";
			WHEN"1100"=>ld<="00100000";
			WHEN"1101"=>ld<="01000000";
			WHEN"1110"=>ld<="10000000";
			WHEN"1111"=>ld<="00000000";
			END CASE;
			END IF;
		  if(SW1='1')then
			elsIF(a="0111")THEN
			a<="0000";
			elsIF(clo'event AND clo='1')THEN
           a<=a+1;
			
		  CASE a IS
		    WHEN"0000"=>ld<="00000000";
			WHEN"0001"=>ld<="00011000";
			WHEN"0010"=>ld<="00111100";
			WHEN"0011"=>ld<="01111110";
			WHEN"0100"=>ld<="11111111";
			WHEN"0101"=>ld<="01111110";
			WHEN"0110"=>ld<="00111100";
			WHEN"0111"=>ld<="00011000";
			WHEN OTHERS=>ld<="00000000";
			END CASE;
			END IF;
			END IF;
			END IF;
			--END IF;
	END PROCESS;
END light_arch;