Subversion Repositories qfp32

-- Copyright (c) 2013 Malte Graeper (mgraep@t-online.de) All rights reserved.

library IEEE;

use IEEE.std_logic_1164.all;

library work;

use work.qfp_p.all;

package qfp32_add_p is

  type qfp32_SCMD_ADD_t is (QFP_ADD,QFP_SUB);

  constant QFP_SCMD_ADD : qfp_scmd_t := "00";

  constant QFP_SCMD_SUB : qfp_scmd_t := "01";

end package qfp32_add_p;

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

library work;

use work.qfp_p.all;

use work.cla_p.all;

use work.qfp32_add_p.all;

entity qfp32_add is

  port (

    clk_i     : in  std_ulogic;

    reset_n_i : in  std_ulogic;

    cmd_i : in qfp_scmd_t;

    start_i : in std_ulogic;

    ready_o : out std_ulogic;

    regA_i : in  qfp32_t;

    regB_i : in  qfp32_t;

    complete_o : out std_ulogic;

    result_o   : out qfp32_raw_t;

    cmp_le_o  : out std_ulogic);-- regA <= regB

end qfp32_add;

architecture Rtl of qfp32_add is

  signal p1_gt : std_ulogic;

  signal p1_fmt : qfp_fmt_t;

  signal p1_mant_a : unsigned(29 downto 0);

  signal p1_mant_b : unsigned(29 downto 0);

  signal p1_cy : std_ulogic;

  signal p1_op_a : unsigned(29 downto 0);

  signal p1_op_b : unsigned(29 downto 0);

  signal p1_clag1 : cla_level_t(7 downto 0);

  signal p1_clag2 : cla_level_t(1 downto 0);

  signal p1_cmp_gt : std_ulogic;

  signal p1_is_add : std_ulogic;

  signal p1_exp1 : std_ulogic_vector(2 downto 0);

  signal p2_complete : std_ulogic;

  signal p2_gt : std_ulogic;

  signal p2_fmt : qfp_fmt_t;

  signal p2_cy : std_ulogic;

  signal p2_op_a : unsigned(29 downto 0);

  signal p2_op_b : unsigned(29 downto 0);

  signal p2_clag1 : cla_level_t(7 downto 0);

  signal p2_clag2 : cla_level_t(1 downto 0);

  signal p2_is_add : std_ulogic;

  signal p2_exp1 : std_ulogic_vector(2 downto 0);

  signal p2_exp2 : std_ulogic_vector(8 downto 0);

  signal p2_result : unsigned(29 downto 0);

  signal p2_sign : std_ulogic;

  signal p2_cmp_gt : std_ulogic;

begin  -- Rtl

  process (clk_i, reset_n_i)

  begin  -- process

    if reset_n_i = '0' then             -- asynchronous reset (active low)

      p2_gt <= '0';

      p2_fmt <= (to_unsigned(0,2),'0');

      p2_is_add <= '0';

      p2_cy <= '0';

      p2_op_a <= to_unsigned(0,30);

      p2_op_b <= to_unsigned(0,30);

      p2_clag1 <= (others => ('0','0'));

      p2_clag2 <= (others => ('0','0'));

      p2_complete <= '0';

      p2_cmp_gt <= '0';

      --p2_exp1 <= (others => '0');-- 6Mhz faster design without this reset value

    elsif clk_i'event and clk_i = '1' then  -- rising clock edge

      p2_complete <= start_i;

      if start_i = '1' then

        p2_gt <= p1_gt;

        p2_fmt <= p1_fmt;

        p2_is_add <= p1_is_add;

        p2_cy <= p1_cy;

        p2_op_a <= p1_op_a;

        p2_op_b <= p1_op_b;

        p2_clag1 <= p1_clag1;

        p2_clag2 <= p1_clag2;

        p2_cmp_gt <= p1_cmp_gt;

        p2_exp1 <= p1_exp1;

      end if;

    end if;

  end process;

  pp: process (cmd_i, p1_clag1, p1_clag2, p1_cy, p1_fmt.exp, p1_gt,

               p1_mant_a(0), p1_mant_a(29 downto 1), p1_mant_b(0),

               p1_mant_b(29 downto 1), p1_op_a, p1_op_b, p2_clag1, p2_exp1,

               p2_exp2, p2_fmt.exp, p2_fmt.sign, p2_is_add, p2_op_a, p2_op_b,

               p2_result(28 downto 0), p2_result(29), p2_sign, regA_i.fmt.exp,

               regA_i.fmt.sign, regA_i.mant, regB_i.fmt.exp, regB_i.fmt.sign,

               regB_i.mant)

  begin  -- process

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

    -- stage 1

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

    -- check if mantissa of regb > rega

    p1_gt <= '0';

    if regb_i.fmt.exp > rega_i.fmt.exp or (regb_i.fmt.exp = rega_i.fmt.exp and fast_gt(regb_i.mant,rega_i.mant)) then

      p1_gt <= '1';

    end if;

    -- adjust mantissa to be aligned

    if regA_i.fmt.exp < regB_i.fmt.exp then

      p1_fmt.exp <= regB_i.fmt.exp;

    else

      p1_fmt.exp <= regA_i.fmt.exp;

    end if;

    -- determine sign

    if p1_gt = '1' then -- b > a

      -- greater value determines sign; invert sign if b > a and will be substracted

      if cmd_i = QFP_SCMD_SUB then

        p1_fmt.sign <= not regB_i.fmt.sign;

      else

        p1_fmt.sign <= regB_i.fmt.sign;

      end if;

    else

      p1_fmt.sign <= regA_i.fmt.sign;

    end if;

    -- extend for rounding

    p1_mant_a <= fast_shift(regA_i.mant & '0',to_integer(p1_fmt.exp-regA_i.fmt.exp)*8,'1');

    p1_mant_b <= fast_shift(regB_i.mant & '0',to_integer(p1_fmt.exp-regB_i.fmt.exp)*8,'1');

    -- negate operands for subtraction

    p1_cy <= '0';

    p1_is_add <= '0';

    p1_op_a <= '0' & p1_mant_a(29 downto 1);

    p1_op_b <= '0' & p1_mant_b(29 downto 1);

    if (cmd_i = QFP_SCMD_ADD and (regA_i.fmt.sign xor regB_i.fmt.sign) = '1') or

       (cmd_i = QFP_SCMD_SUB and (regA_i.fmt.sign xor regB_i.fmt.sign) = '0') then

      -- substraction

      if p1_gt = '1' then

        p1_op_a <= not ('0' & p1_mant_a(29 downto 1));

        p1_cy <= not p1_mant_a(0);-- use rounding

      else

        p1_op_b <= not ('0' & p1_mant_b(29 downto 1));

        p1_cy <= not p1_mant_b(0);-- use rounding

      end if;

    else -- addition

      p1_cy <= p1_mant_a(0) or p1_mant_b(0);-- rounding up

      p1_is_add <= '1';

    end if;

    -- calc greater than b > a

    p1_cmp_gt <= p1_gt;

    if regA_i.fmt.sign /= regB_i.fmt.sign then

      p1_cmp_gt <= regA_i.fmt.sign;

    elsif regA_i.fmt.sign = '1' then

      p1_cmp_gt <= not p1_gt;

    end if;

    -- calculate pre carry (first level of carray lookahead adder)

    p1_clag1 <= CLALevelMk(p1_op_a,p1_op_b,4);

    -- second level

    p1_clag2 <= CLALevelMk(p1_clag1,4);

    -- expand first level carry

    p1_exp1 <= CLAExpandCy(p1_clag2,p1_cy);

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

    -- stage 2

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

    -- expand second level carry

    p2_exp2 <= CLAExpandCy(p2_clag1,p2_exp1);

    -- propagate carry (level 2)

    p2_result <= CLAParallelAdd(p2_op_a,p2_op_b,p2_exp2);

    p2_sign <= p2_fmt.sign;

    result_o.extMant <= p2_result(28 downto 0) & (23 downto 0 => '0');

    result_o.ov <= "0000" & (p2_result(29) and p2_is_add); -- allow overflow only for real additions

    result_o.exp <= '0' & p2_fmt.exp;

    result_o.sign <= p2_sign;-- and not p2_cmp_eq;

  end process pp;

  cmp_le_o <= not p2_cmp_gt;-- less equal than

  ready_o <= '1';

  complete_o <= p2_complete;

end Rtl;