--Importation des bibliothèques
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;

-- Description de l'interface externe
entity COMPARATEUR2bits is port(
    A,B : IN STD_LOGIC_VECTOR (1 dowto 0); -- A et B sont des mots de 2bits : A = A1A0 et B = B1B0
    S : OUT STD_LOGIC;
end COMPARATEUR2bits;

-- Description structurelle
architecture EQU_LOG of COMPARATEUR2bits
begin
    S <= ( not(A(1)) and not(A(0)) and not(B(1)) and not(B(0)))
         or (not(A(1)) and A(0) and not(B(1)) and B(0))
         or (A(1) and not(A(0)) and B(1) and not(B(0)))
         or (A(1) and A(0) and B(1) and B(0));
end EQU_LOG;