-- dec2to4.vhd

            LIBRARY ieee;
            USE ieee.std_logic_1164.all;
            USE ieee.std_logic_arith.all;

            ENTITY dec2to4 IS
            PORT (  a : in std_logic_vector(1 downto 0);
                        o : out std_logic_vector(3 downto 0));
            END dec2to4 ;

            ARCHITECTURE maxpld OF dec2to4 IS
            BEGIN 
               PROCESS
                  begin
                           case a is
                                         when "00" => o <= "0001";
                                         when "01" => o <= "0010";
                                         when "10" => o <= "0100";
                                         when others => o <= "1000";
                   end case;
               END  PROCESS;
            END maxpld;