Subversion Repositories fpu100

-------------------------------------------------------------------------------

--

-- Project:     <Floating Point Unit Core>

--      

-- Description: post-normalization entity for the division unit

-------------------------------------------------------------------------------

--

--                              100101011010011100100

--                              110000111011100100000

--                              100000111011000101101

--                              100010111100101111001

--                              110000111011101101001

--                              010000001011101001010

--                              110100111001001100001

--                              110111010000001100111

--                              110110111110001011101

--                              101110110010111101000

--                              100000010111000000000

--

--      Author:          Jidan Al-eryani 

--      E-mail:          jidan@gmx.net

--

--  Copyright (C) 2006

--

--      This source file may be used and distributed without        

--      restriction provided that this copyright statement is not   

--      removed from the file and that any derivative work contains 

--      the original copyright notice and the associated disclaimer.

--                                                           

--              THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     

--      EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   

--      TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   

--      FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      

--      OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         

--      INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    

--      (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   

--      GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        

--      BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  

--      LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  

--      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  

--      OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         

--      POSSIBILITY OF SUCH DAMAGE. 

--

library ieee ;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

use ieee.std_logic_misc.all;

library work;

use work.fpupack.all;

entity post_norm_div is

        port(

                         clk_i                          : in std_logic;

                         opa_i                          : in std_logic_vector(FP_WIDTH-1 downto 0);

                         opb_i                          : in std_logic_vector(FP_WIDTH-1 downto 0);

                         qutnt_i                        : in std_logic_vector(FRAC_WIDTH+3 downto 0);

                         rmndr_i                        : in std_logic_vector(FRAC_WIDTH+3 downto 0);

                         exp_10_i                       : in std_logic_vector(EXP_WIDTH+1 downto 0);

                         sign_i                         : in std_logic;

                         rmode_i                        : in std_logic_vector(1 downto 0);

                         output_o                       : out std_logic_vector(FP_WIDTH-1 downto 0);

                         ine_o                          : out std_logic

                );

end post_norm_div;

architecture rtl of post_norm_div is

-- input&output register signals

signal s_opa_i, s_opb_i : std_logic_vector(FP_WIDTH-1 downto 0);

signal s_expa, s_expb : std_logic_vector(EXP_WIDTH-1 downto 0);

signal s_qutnt_i, s_rmndr_i : std_logic_vector(FRAC_WIDTH+3 downto 0);

signal s_r_zeros        : std_logic_vector(5 downto 0);

signal s_exp_10_i                       : std_logic_vector(EXP_WIDTH+1 downto 0);

signal s_sign_i                         : std_logic;

signal s_rmode_i                        : std_logic_vector(1 downto 0);

signal s_output_o                        : std_logic_vector(FP_WIDTH-1 downto 0);

signal s_ine_o, s_overflow : std_logic;

signal s_opa_dn, s_opb_dn : std_logic;

signal s_qutdn : std_logic;

signal s_shr1, s_shl1 : std_logic_vector(5 downto 0);

signal s_shr2 : std_logic;

signal s_expo1, s_expo2, s_expo3 : std_logic_vector(8 downto 0);

signal s_fraco1 : std_logic_vector(26 downto 0);

signal s_frac_rnd, s_fraco2 : std_logic_vector(24 downto 0);

signal s_guard, s_round, s_sticky, s_roundup : std_logic;

signal s_lost : std_logic;

signal s_op_0, s_opab_0 : std_logic;

signal s_infa, s_infb : std_logic;

signal s_nan_in, s_nan_op, s_nan_a, s_nan_b : std_logic;

signal s_exp_10b : std_logic_vector(9 downto 0);

begin

        -- Input Register

        process(clk_i)

        begin

                if rising_edge(clk_i) then

                        s_opa_i <= opa_i;

                        s_opb_i <= opb_i;

                        s_expa <= opa_i(30 downto 23);

                        s_expb <= opb_i(30 downto 23);

                        s_qutnt_i <= qutnt_i;

                        s_rmndr_i <= rmndr_i;

                        s_exp_10_i <= exp_10_i;

                        s_sign_i <= sign_i;

                        s_rmode_i <= rmode_i;

                end if;

        end process;

        -- Output Register

        process(clk_i)

        begin

                if rising_edge(clk_i) then

                        output_o <= s_output_o;

                        ine_o   <= s_ine_o;

                end if;

        end process;

    -- qutnt_i

    -- 26 25                    3

    -- |  |                     | 

    -- h  fffffffffffffffffffffff grs

        --*** Stage 1 ****

        -- figure out the exponent and howmuch the fraction has to be shiftd right/left

        s_opa_dn <= '1' when or_reduce(s_expa)='0' and or_reduce(opa_i(22 downto 0))='1' else '0';

        s_opb_dn <= '1' when or_reduce(s_expb)='0' and or_reduce(opb_i(22 downto 0))='1' else '0';

        s_qutdn <= not s_qutnt_i(26);

        s_exp_10b <= s_exp_10_i - ("000000000"&s_qutdn);

        process(clk_i)

                variable v_shr, v_shl : std_logic_vector(9 downto 0);

        begin

                if rising_edge(clk_i) then

                if s_exp_10b(9)='1' or s_exp_10b="0000000000" then

                        v_shr := ("0000000001" - s_exp_10b) - s_qutdn;

                        v_shl := (others =>'0');

                        s_expo1 <= "000000001";

                elsif s_exp_10b(8)='1' then

                        v_shr := (others =>'0');

                        v_shl := (others =>'0');

                        s_expo1 <= "011111111";

                else

                        v_shr := (others =>'0');

                        v_shl :=  "000000000"& s_qutdn;

                        s_expo1 <= s_exp_10b(8 downto 0);

                end if;

                if  v_shr(6)='1' then

                        s_shr1 <= "111111";

                else

                        s_shr1 <= v_shr(5 downto 0);

                end if;

                s_shl1 <= v_shl(5 downto 0);

                end if;

        end process;

        -- *** Stage 2 ***

        -- Shifting the fraction and rounding

        -- shift the fraction

        process(clk_i)

        begin

                if rising_edge(clk_i) then

                        if s_shr1 /= "000000" then

                                s_fraco1 <= shr(s_qutnt_i, s_shr1);

                        else

                                s_fraco1 <= shl(s_qutnt_i, s_shl1);

                        end if;

                end if;

        end process;

        s_expo2 <= s_expo1 - "000000001" when s_fraco1(26)='0' else s_expo1;

        s_r_zeros <= count_r_zeros(s_qutnt_i);

        s_lost <= '1' when (s_shr1+("00000"&s_shr2)) > s_r_zeros else '0';

        -- ***Stage 3***

        -- Rounding

        s_guard <= s_fraco1(2);

        s_round <= s_fraco1(1);

        s_sticky <= s_fraco1(0) or or_reduce(s_rmndr_i);

        s_roundup <= s_guard and ((s_round or s_sticky)or s_fraco1(3)) when s_rmode_i="00" else -- round to nearset even

                                 ( s_guard or s_round or s_sticky) and (not s_sign_i) when s_rmode_i="10" else -- round up

                                 ( s_guard or s_round or s_sticky) and (s_sign_i) when s_rmode_i="11" else -- round down

                                 '0'; -- round to zero(truncate = no rounding)

        s_frac_rnd <= ("0"&s_fraco1(26 downto 3)) + '1' when s_roundup='1' else "0"&s_fraco1(26 downto 3);

        s_shr2 <= s_frac_rnd(24);

        process(clk_i)

        begin

                if rising_edge(clk_i) then

                        if s_shr2='1' and s_expo2 /= "011111111" then

                                s_expo3 <= s_expo2 + "1";

                                s_fraco2 <= "0"&s_frac_rnd(24 downto 1);

                        else

                                s_expo3 <= s_expo2;

                                s_fraco2 <= s_frac_rnd;

                        end if;

                end if;

        end process;

        ---

        ---***Stage 4****

        -- Output

        s_op_0 <= not ( or_reduce(s_opa_i(30 downto 0)) and or_reduce(s_opb_i(30 downto 0)) );

        s_opab_0 <= not ( or_reduce(s_opa_i(30 downto 0)) or or_reduce(s_opb_i(30 downto 0)) );

        s_infa <= '1' when s_expa="11111111"  else '0';

        s_infb <= '1' when s_expb="11111111"  else '0';

        s_nan_a <= '1' when (s_infa='1' and or_reduce (s_opa_i(22 downto 0))='1') else '0';

        s_nan_b <= '1' when (s_infb='1' and or_reduce (s_opb_i(22 downto 0))='1') else '0';

        s_nan_in <= '1' when s_nan_a='1' or  s_nan_b='1' else '0';

        s_nan_op <= '1' when (s_infa and s_infb)='1' or s_opab_0='1' else '0';-- 0 / 0, inf / inf

        s_overflow <= '1' when s_expo3 = "011111111" and (s_infa or s_infb)='0' and or_reduce(s_opb_i(30 downto 0))='1' else '0';

        s_ine_o <= '1' when s_op_0='0' and (s_lost or or_reduce(s_fraco1(2 downto 0)) or s_overflow or or_reduce(s_rmndr_i))='1' else '0';

        process(s_sign_i, s_expo3, s_fraco2, s_nan_in, s_nan_op, s_infa, s_infb, s_overflow)

        begin

                if (s_nan_in or s_nan_op)='1' then

                        s_output_o <= s_sign_i & QNAN;

                elsif (s_infa or s_infb)='1' or s_overflow='1' then

                                s_output_o <= s_sign_i & INF;

                else

                                s_output_o <= s_sign_i & s_expo3(7 downto 0) & s_fraco2(22 downto 0);

                end if;

        end process;

end rtl;