实验程序如下:
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY CS_LED IS
PORT ( CLK : IN STD_LOGIC;
SG : OUT STD_LOGIC_VECTOR(6 DOWNTO 0);
BT : OUT STD_LOGIC_VECTOR(7 DOWNTO 0) );
END;
ARCHITECTURE one OF CS_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 CNT8 <= CNT8 + 1;
END IF;
END PROCESS P2 ;
P3: PROCESS( A )
BEGIN
CASE A IS
WHEN 0 => SG <= "0111111"; WHEN 1 => SG <= "0000110";
WHEN 2 => SG <= "1011011"; WHEN 3 => SG <= "1001111";
WHEN 4 => SG <= "1100110"; WHEN 5 => SG <= "1101101";
WHEN 6 => SG <= "1111101"; WHEN 7 => SG <= "0000111";
WHEN 8 => SG <= "1111111"; WHEN 9 => SG <= "1101111";
WHEN 10 => SG <= "1110111"; WHEN 11 => SG <= "1111100";
WHEN 12 => SG <= "0111001"; WHEN 13 => SG <= "1011110";
WHEN 14 => SG <= "1111001"; WHEN 15 => SG <= "1110001";
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