八選一須具選擇器：用CASE語句。

LIBRARY    IEEE;
USE      IEEE.STD_LOGIC_1164.ALL;
ENTITY      mux_8_1      IS
  PORT (A,B,C,D,E,F,G,H,En:IN STD_LOGIC;
         S:in STD_LOGIC_vector(2 downto 0);
         Y: out STD_LOGIC);
end     mux_8_1;
ARCHITECTURE     mux   OF     mux_8_1     IS
begin
  process( S,A,B,C,D,E,F,G,H,En)
     begin
       if En='0' then
          case  S   is
           when "000" => Y<=A;
           when "001" => Y<=B;
           when "010" => Y<=C;
           when "011" => Y<=D;
           when "100" => Y<=E;
           when "101" => Y<=F;
           when "110" => Y<=G;
           when "111" => Y<=H;
          end case;
       end if;
    end process;
  end  mux;

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