Subversion Repositories special_functions_unit

-- Log2 IEEE754 case detect

library ieee;

        use ieee.std_logic_1164.all;

        use ieee.numeric_std.all;

entity rsqrt_ieee is

        port      (i_data                                       : in    std_logic_vector(31 downto 0);

                                o_case                                  : out std_logic_vector(31 downto 0);

                                o_case_en                               : out std_logic);

end entity;

architecture rtl of rsqrt_ieee is

        signal s_sgn    : std_logic;

        signal s_exp    : std_logic_vector(7 downto 0);

        signal s_mantis: std_logic_vector(22 downto 0);

begin

        s_sgn   <= i_data(i_data'left);

        s_exp   <= i_data(i_data'left-1 downto 23);

        s_mantis        <= i_data(22 downto 0);

        process(s_sgn, s_exp, s_mantis)

        begin

                if s_sgn = '1' then

                        o_case_en       <= '1';

                        if s_exp = X"00" then

                                o_case <= X"FF800000";          -- -inf

                        else

                                o_case <= X"FFFFFFFF";          -- NaN

                        end if;

                else

                        if s_exp = X"00" then

                                o_case_en       <= '1';

                                o_case <= X"7F800000";          -- +inf

                        elsif s_exp = X"FF" then

                                o_case_en       <= '1';

                                if s_mantis = "00000000000000000000000" then

                                        o_case <= X"00000000";

                                else

                                        o_case <= X"FFFFFFFF"; -- NaN

                                end if;

                        else

                                o_case_en       <= '0';

                                o_case <= X"FFFFFFFF";          -- (dont care)

                        end if;

                end if;

        end process;

end rtl;