scan_led.vhd

一个8位数码管扫描程序,经过编译和仿真.

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY scan_led IS
  PORT(clk:IN STD_LOGIC;
        sg:OUT STD_LOGIC_VECTOR(6 DOWNTO 0);
        bt:OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END scan_led;
ARCHITECTURE m OF scan_led IS
   SIGNAL cnt8:STD_LOGIC_VECTOR(2 DOWNTO 0);
   SIGNAL    a:INTEGER RANGE 0 TO 15;
  BEGIN
    p1:PROCESS(cnt8)
         BEGIN
           CASE cnt8 IS
             WHEN "000"=>bt<="00000001";a<=1;
             WHEN "001"=>bt<="00000010";a<=3;				
			 WHEN "010"=>bt<="00000100";a<=5;
			 WHEN "011"=>bt<="00001000";a<=7;
			 WHEN "100"=>bt<="00010000";a<=9;
			 WHEN "101"=>bt<="00100000";a<=11;
			 WHEN "110"=>bt<="01000000";a<=13;
			 WHEN "111"=>bt<="10000000";a<=15;
			 WHEN OTHERS=>NULL;
		   END CASE;
		END PROCESS p1;
    p2:PROCESS(clk)
       BEGIN
        IF(clk'EVENT AND clk='1')  THEN
            IF(cnt8="111") THEN
               cnt8<="000";
            ELSE
               cnt8<=cnt8+1;
            END IF;
        END IF;
      END PROCESS p2;
   p3:PROCESS(cnt8)
     BEGIN
        CASE cnt8 IS
           WHEN "000"=>sg<="0000110";
           WHEN "001"=>sg<="1001111";
           WHEN "010"=>sg<="1101101";
           WHEN "011"=>sg<="0000111";
           WHEN "100"=>sg<="1100111";
           WHEN "101"=>sg<="1111100";
           WHEN "110"=>sg<="1011110";
           WHEN "111"=>sg<="1110001";
        END CASE;
     END PROCESS p3;
 END m;