vhdl语言编程实例

实现各种逻辑功能：

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY louji1a IS

PORT(S: IN STD_LOGIC_VECTOR(2 DOWNTO 0);

C: IN STD_LOGIC;

A: IN STD_LOGIC_VECTOR(4 DOWNTO 0);

B: IN STD_LOGIC_VECTOR(4 DOWNTO 0);

F: OUT STD_LOGIC_VECTOR(4 DOWNTO 0)

);

END ENTITY louji1a;

ARCHITECTURE ONE OF louji1a IS

BEGIN

F<=A WHEN S="000" ELSE

A-B WHEN S="001" ELSE

A-1 WHEN (S="010" AND C='0') ELSE

A+1 WHEN (S="011" AND C='0') ELSE

A AND B WHEN S="100" ELSE

A OR B WHEN S="101" ELSE

A XOR B WHEN S="110" ELSE

NOT A WHEN S="111" ELSE

NULL;

END ARCHITECTURE ONE;

38译码器：

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

ENTITY yimaqi1a IS

PORT(A: IN STD_LOGIC_VECTOR(3 DOWNTO 0);

B: OUT STD_LOGIC_VECTOR(6 DOWNTO 0)

);

END ENTITY yimaqi1a;

ARCHITECTURE one OF yimaqi1a IS

--SIGNAL abc:STD_LOGIC_VECTOR(3 DOWNTO 0);

--SIGNAL def:STD_LOGIC_VECTOR(6 DOWNTO 0);

BEGIN

--abc<=A3&A2&A1&A0;

--def<=g&f&e&d&c&b&a;

PROCESS (A)

BEGIN

case A IS

WHEN"0000"=>B<="0111111";

WHEN"0001"=>B<="0000110";

WHEN"0010"=>B<="1011011";

WHEN"0011"=>B<="1001111";

WHEN"0100"=>B<="1100110";

WHEN"0101"=>B<="1101101";

WHEN"0110"=>B<="1111101";

WHEN"0111"=>B<="0000111";

WHEN"1000"=>B<="1111111";

WHEN"1001"=>B<="1101111";

WHEN"1010"=>B<="1110111";

WHEN"1011"=>B<="1111100";

WHEN"1100"=>B<="0111001";

WHEN"1101"=>B<="1011110";

WHEN"1110"=>B<="1111001";

WHEN"1111"=>B<="1110001";

WHEN OTHERS =>NULL;

END CASE ;

END PROCESS;

END ARCHITECTURE ONE;

十进制计数器：

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY jishuqi1a IS

PORT(CLK,EN,CTRL,CLR:IN STD_LOGIC;

Q:OUT STD_LOGIC_VECTOR(3 DOWNTO 0);

CO:OUT STD_LOGIC);

END ENTITY jishuqi1a;

ARCHITECTURE BHV OF jishuqi1a IS

SIGNAL QQ :STD_LOGIC_VECTOR(3 DOWNTO 0);

BEGIN

PROCESS(CLK,EN,CTRL,CLR)

--VARIABLE QQ :STD_LOGIC_VECTOR(3 DOWNTO 0);

BEGIN

IF CLR='0' THEN QQ<="0000";

ELSIF CTRL='0' THEN QQ<="0000";

ELSIF CLK'EVENT AND CLK='1'

THEN IF EN='1' THEN IF QQ<9 THEN QQ<=QQ+1;E