function기능을 이용해서 multimux를 구현해 보겠습니다.

DUT

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity multimux is
    Port ( X : in std_logic_vector( 3 downto 0);
        S : in std_logic_vector( 2 downto 0);
        Y : out std_logic );
        
end multimux;

architecture Behavioral of multimux is

function Mux(x0 : in std_logic; x1 : in std_logic; s : in std_logic) return std_logic is
begin
    if s = '0' then
        return x0;
    else
        return x1;
    end if;
end function;

signal F : std_logic_vector( 1 downto 0 );

begin

F(0) <= Mux(X(0), X(1), S(0));
F(1) <= Mux(X(2), X(3), S(1));
Y <= Mux(F(0), F(1), S(2));

end Behavioral;

테스트벤치는 그대로

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity tb_multimux is
end tb_multimux;

architecture Behavioral of tb_multimux is
    signal input : std_logic_vector(3 downto 0);
    signal sel : std_logic_vector(2 downto 0);
    signal output : std_logic;

begin
UUT : entity work.multimux port map
(x => input, y => output, s => sel);

process
    begin
    input <= "0101";
    
    sel <= "000";
    wait for 10ns;
    
    sel <= "001";
    wait for 10ns;
    
    sel <= "010";
    wait for 10ns;
    
    sel <= "011";
    wait for 10ns;    

    sel <= "100";
    wait for 10ns;
    
    sel <= "101";
    wait for 10ns;
    
    sel <= "110";
    wait for 10ns;
    
    sel <= "111";
    wait for 10ns;
    
    report "종료" severity failure;
end process;

end Behavioral;

Waveform