src/pre_norm_sqrt.vhd

   1 -------------------------------------------------------------------------------
   2 --
   3 -- Project:     <Floating Point Unit Core>
   4 --
   5 -- Description: pre-normalization entity for the square-root unit
   6 -------------------------------------------------------------------------------
   7 --
   8 --                              100101011010011100100
   9 --                              110000111011100100000
  10 --                              100000111011000101101
  11 --                              100010111100101111001
  12 --                              110000111011101101001
  13 --                              010000001011101001010
  14 --                              110100111001001100001
  15 --                              110111010000001100111
  16 --                              110110111110001011101
  17 --                              101110110010111101000
  18 --                              100000010111000000000
  19 --
  20 --      Author:          Jidan Al-eryani
  21 --      E-mail:          [email protected]
  22 --
  23 --  Copyright (C) 2006
  24 --
  25 --      This source file may be used and distributed without
  26 --      restriction provided that this copyright statement is not
  27 --      removed from the file and that any derivative work contains
  28 --      the original copyright notice and the associated disclaimer.
  29 --
  30 --              THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY
  31 --      EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  32 --      TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  33 --      FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR
  34 --      OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  35 --      INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  36 --      (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  37 --      GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  38 --      BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  39 --      LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT
  40 --      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  41 --      OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  42 --      POSSIBILITY OF SUCH DAMAGE.
  43 --
  44
  45 library ieee ;
  46 use ieee.std_logic_1164.all;
  47 use ieee.std_logic_unsigned.all;
  48 use ieee.std_logic_misc.all;
  49
  50 library work;
  51 use work.fpupack.all;
  52
  53 entity pre_norm_sqrt is
  54         port(
  55                          clk_i                  : in std_logic;
  56                          opa_i                  : in std_logic_vector(FP_WIDTH-1 downto 0);
  57                          fracta_52_o    : out std_logic_vector(2*(FRAC_WIDTH+3)-1 downto 0);
  58                          exp_o                  : out std_logic_vector(EXP_WIDTH-1 downto 0)
  59                 );
  60 end pre_norm_sqrt;
  61
  62 architecture rtl of pre_norm_sqrt is
  63
  64 signal s_expa : std_logic_vector(EXP_WIDTH-1 downto 0);
  65 signal s_exp_o, s_exp_tem : std_logic_vector(EXP_WIDTH downto 0);
  66 signal s_fracta : std_logic_vector(FRAC_WIDTH-1 downto 0);
  67 signal s_fracta_24 : std_logic_vector(FRAC_WIDTH downto 0);
  68 signal s_fracta_52_o, s_fracta1_52_o, s_fracta2_52_o : std_logic_vector(2*(FRAC_WIDTH+3)-1 downto 0);
  69 signal s_sqr_zeros_o : std_logic_vector(5 downto 0);
  70
  71
  72 signal s_opa_dn : std_logic;
  73
  74 begin
  75
  76         s_expa <= opa_i(30 downto 23);
  77         s_fracta <= opa_i(22 downto 0);
  78
  79
  80         exp_o <= s_exp_o(7 downto 0);
  81         fracta_52_o <= s_fracta_52_o;
  82
  83         -- opa or opb is denormalized
  84         s_opa_dn <= not or_reduce(s_expa);
  85
  86         s_fracta_24 <= (not s_opa_dn) & s_fracta;
  87
  88         -- count leading zeros
  89         s_sqr_zeros_o <= count_l_zeros(s_fracta_24 );
  90
  91         -- adjust the exponent
  92         s_exp_tem <= ("0"&s_expa)+"001111111" - ("000"&s_sqr_zeros_o);
  93
  94         process(clk_i)
  95         begin
  96                 if rising_edge(clk_i) then
  97                         if or_reduce(opa_i(30 downto 0))='1' then
  98                                 s_exp_o <= ("0"&s_exp_tem(8 downto 1));
  99                         else
 100                                 s_exp_o <= "000000000";
 101                         end if;
 102                 end if;
 103         end process;
 104
 105         -- left-shift the radicand
 106         s_fracta1_52_o <= shl(s_fracta_24, s_sqr_zeros_o) & "0000000000000000000000000000";
 107         s_fracta2_52_o <= '0' & shl(s_fracta_24, s_sqr_zeros_o) & "000000000000000000000000000";
 108
 109         s_fracta_52_o <= s_fracta1_52_o when s_expa(0)='0' else s_fracta2_52_o;
 110
 111 end rtl;