Subversion Repositories floating_point_adder_subtractor

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

entity addsub is

port

        ( input_a,input_b : in std_logic_vector(32 downto 0);

          msb_ab : in std_logic_vector(1 downto 0);

          clk,reset,finish_shift,add_sub : in std_logic;

          finish_addsub : out std_logic;

      output_result : out std_logic_vector(33 downto 0)

        );      -- input_a larger after swap, inpu_b shifted according to 

end addsub;

architecture addsub of addsub is

begin

process(clk,input_a,input_b,clk,reset,finish_shift,add_sub,msb_ab)

variable man_a,man_b,temp : std_logic_vector(24 downto 0);

variable exp_a : std_logic_vector(7 downto 0);

variable msb_a,msb_b : std_logic;

begin

if (reset='1' or finish_shift='0') then

        output_result<="0000000000000000000000000000000000";

        finish_addsub<='0';

elsif( reset='0' and finish_shift='1' and input_a="0000000000000000000000000000000000" and

     input_b="0000000000000000000000000000000000" ) then

        output_result<="0000000000000000000000000000000000";

        finish_addsub<='1';

elsif( reset='0' and finish_shift='1') then

        exp_a:=input_a(31 downto 24);

        man_a:='0' & input_a(23 downto 0);

        man_b:='0' & input_b(23 downto 0);

        msb_a:=input_a(32);

        msb_b:=input_b(32);

        if (add_sub='0') then  -- subtraction

          if( msb_ab="00" or msb_ab="11")then       --if both same sign then subtract

          temp:= man_a - man_b;                                     --mantissa

          elsif( msb_ab="01" or msb_ab="10") then   --if un equal sign, add mantissa

          temp:= man_a + man_b;

          end if;

        end if;

        if (add_sub='1') then

          if( msb_ab="00" or msb_ab="11")then

          temp:= man_a + man_b;

          elsif( msb_ab="01" or msb_ab="10") then

          temp:= man_a - man_b;

          end if;

        end if;

output_result <= msb_a & exp_a & temp;

finish_addsub <= '1';

end if;

end process;

end addsub;