4选1多路选择器（case-when实现）

4选1多路选择器（case-when实现）：

 

LIBRARY IEEE;

USE IEEE.STD_LOGICD_1164.ALL;

 

ENTITY chooes IS

PORT( S1，S0: IN STD_LOGIC;

             a,b,c,d: IN STD_LOGIC);

                      Z: OUT STD_LOGIC

          );

END chooes;

 

ARCHITECTURE art1 OF chooes IS

SIGNAL s: STD_LOGICVECTOR(1 DOWNTO 0);

BEGIN

     PROCESS(S1,S0,a,b,c,d)

     BEGIN

           s<=S1 & S0;

           CASE S IS

                  WHEN "00" => Z<=a;

                  WHEN "01" => Z<=b;

                  WHEN "10" => Z<=c;

                  WHEN "11" => Z<=d;

                  WHEN OTHERS => NULL;

            END CASE;

    END PROCESS;

END art1;