Subversion Repositories fpu100

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

--

-- Project:     <Floating Point Unit Core>

--      

-- Description: pre-normalization entity for the square-root 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 pre_norm_sqrt is

        port(

                         clk_i                  : in std_logic;

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

                         fracta_52_o    : out std_logic_vector(2*(FRAC_WIDTH+3)-1 downto 0);

                         exp_o                  : out std_logic_vector(EXP_WIDTH-1 downto 0)

                );

end pre_norm_sqrt;

architecture rtl of pre_norm_sqrt is

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

signal s_exp_o, s_exp_tem : std_logic_vector(EXP_WIDTH downto 0);

signal s_fracta : std_logic_vector(FRAC_WIDTH-1 downto 0);

signal s_fracta_24 : std_logic_vector(FRAC_WIDTH downto 0);

signal s_fracta_52_o, s_fracta1_52_o, s_fracta2_52_o : std_logic_vector(2*(FRAC_WIDTH+3)-1 downto 0);

signal s_sqr_zeros_o : std_logic_vector(5 downto 0);

signal s_opa_dn : std_logic;

begin

        s_expa <= opa_i(30 downto 23);

        s_fracta <= opa_i(22 downto 0);

        exp_o <= s_exp_o(7 downto 0);

        fracta_52_o <= s_fracta_52_o;

        -- opa or opb is denormalized

        s_opa_dn <= not or_reduce(s_expa);

        s_fracta_24 <= (not s_opa_dn) & s_fracta;

        -- count leading zeros

        s_sqr_zeros_o <= count_l_zeros(s_fracta_24 );

        -- adjust the exponent

        s_exp_tem <= ("0"&s_expa)+"001111111" - ("000"&s_sqr_zeros_o);

        process(clk_i)

        begin

                if rising_edge(clk_i) then

                        if or_reduce(opa_i(30 downto 0))='1' then

                                s_exp_o <= ("0"&s_exp_tem(8 downto 1));

                        else

                                s_exp_o <= "000000000";

                        end if;

                end if;

        end process;

        -- left-shift the radicand      

        s_fracta1_52_o <= shl(s_fracta_24, s_sqr_zeros_o) & "0000000000000000000000000000";

        s_fracta2_52_o <= '0' & shl(s_fracta_24, s_sqr_zeros_o) & "000000000000000000000000000";

        s_fracta_52_o <= s_fracta1_52_o when s_expa(0)='0' else s_fracta2_52_o;

end rtl;