FULL ADDER / FULL SUBTRACTOR USING MODE CONTROL

library ieee;

use ieee.std_logic_1164.all;

Entity FA_FS is

port( M , A , B ,C : in std_logic;

            SUM / DIFF ,CARRY / BORW :out std_logic );

end FA_FS;

Architecture Behavioral of  FA_FS is

begin

process( M , A , B ,C )

begin

if M='0' then

if A='0' then SUM / DIFF <=B xor C ; CARRY / BORW<=B and C;

else SUM / DIFF <=B xnor C ; CARRY / BORW<=B nand C;

end if;

else

if A='0' then SUM / DIFF <=B xor C ; CARRY / BORW<=B nand C;

else SUM / DIFF <=B xnor C ; CARRY / BORW<=B and C;

end if;

end if;

end process;

end Behavioral;