Subversion Repositories mod_sim_exp

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

----  modulus_ram_asym                                            ---- 

----                                                              ---- 

----  This file is part of the                                    ----

----    Modular Simultaneous Exponentiation Core project          ---- 

----    http://www.opencores.org/cores/mod_sim_exp/               ---- 

----                                                              ---- 

----  Description                                                 ---- 

----    BRAM memory and logic to store the modulus, due to the    ----

----    achitecture, a minimum depth of 2 is needed for this      ----

----    module to be inferred into blockram, this version is      ----

----    slightly more performant than modulus_ram_gen and uses    ----

----    less resources. but does not work on every fpga, only     ----

----    the ones that support asymmetric rams.                    ----

----                                                              ---- 

----  Dependencies:                                               ----

----    - dpramblock_asym                                         ----

----                                                              ----

----  Authors:                                                    ----

----      - Geoffrey Ottoy, DraMCo research group                 ----

----      - Jonas De Craene, JonasDC@opencores.org                ---- 

----                                                              ---- 

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

----                                                              ---- 

---- Copyright (C) 2011 DraMCo research group and OPENCORES.ORG   ---- 

----                                                              ---- 

---- 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 source file is free software; you can redistribute it   ---- 

---- and/or modify it under the terms of the GNU Lesser General   ---- 

---- Public License as published by the Free Software Foundation; ---- 

---- either version 2.1 of the License, or (at your option) any   ---- 

---- later version.                                               ---- 

----                                                              ---- 

---- This source is distributed in the hope that it will be       ---- 

---- useful, but WITHOUT ANY WARRANTY; without even the implied   ---- 

---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ---- 

---- PURPOSE.  See the GNU Lesser General Public License for more ---- 

---- details.                                                     ---- 

----                                                              ---- 

---- You should have received a copy of the GNU Lesser General    ---- 

---- Public License along with this source; if not, download it   ---- 

---- from http://www.opencores.org/lgpl.shtml                     ---- 

----                                                              ---- 

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

library mod_sim_exp;

use mod_sim_exp.std_functions.all;

use mod_sim_exp.mod_sim_exp_pkg.all;

-- structural description of a RAM to hold the modulus, with 

-- adjustable width (64, 128, 256, 512, 576, 640,..) and depth(nr of moduluses)

--    formula for available widths: (i*512+(0 or 64 or 128 or 256)) (i=integer number) 

--

entity modulus_ram_asym is

  generic(

    width : integer := 1536;  -- must be a multiple of 32

    depth : integer := 2;     -- nr of moduluses

    device : string := "xilinx"

  );

  port(

    clk            : in std_logic;

      -- bus side

    write_modulus  : in std_logic; -- write enable

    modulus_in_sel : in std_logic_vector(log2(depth)-1 downto 0); -- modulus operand to write to

    modulus_addr   : in std_logic_vector(log2((width)/32)-1 downto 0); -- modulus word(32-bit) address

    modulus_in     : in std_logic_vector(31 downto 0); -- modulus word data in

    modulus_sel    : in std_logic_vector(log2(depth)-1 downto 0); -- selects the modulus to use for multiplications

      -- multiplier side

    modulus_out    : out std_logic_vector(width-1 downto 0)

  );

end modulus_ram_asym;

architecture structural of modulus_ram_asym is

  -- constants

  constant RAMblock_maxwidth   : integer := 512;

  constant nrRAMblocks_full    : integer := width/RAMblock_maxwidth;

  constant RAMblock_part       : integer := width rem RAMblock_maxwidth;

  constant RAMblock_part_width : integer := width-(nrRAMblocks_full*RAMblock_maxwidth);

  constant RAMselect_aw        : integer := log2(width/32)-log2(nrRAMblocks_full/32);

begin

  -- generate (width/512) ramblocks with a given depth

  -- these rams are tyed together to form the following structure

  --  dual port ram:

  --  - PORT A : 32-bit write

  --  - PORT B : (width)-bit read

  -- 

  single_block : if (width <= RAMblock_maxwidth) generate

    signal waddr : std_logic_vector(log2((width*depth)/32)-1 downto 0);

  begin

    waddr <= modulus_in_sel & modulus_addr;

    ramblock: dpramblock_asym

    generic map(

      width => width,

      depth => depth,

      device  => device

    )

    port map(

      clk => clk,

      -- write port

      waddr => waddr,

      we    => write_modulus,

      din   => modulus_in,

      -- read port

      raddr => modulus_sel,

      dout  => modulus_out

    );

  end generate;

  multiple_full_blocks : if (width > RAMblock_maxwidth) generate

    -- signals for multiple blocks

    signal waddr  : std_logic_vector(log2(RAMblock_maxwidth*depth/32)-1 downto 0);

    signal we_RAM : std_logic_vector(nrRAMblocks_full-1 downto 0);

  begin

    ramblocks_full : for i in 0 to nrRAMblocks_full generate

      -- write port signal

      waddr <= modulus_in_sel & modulus_addr(log2(RAMblock_maxwidth/32)-1 downto 0);

      full_ones : if (i < nrRAMblocks_full) generate

        ramblock_full : dpramblock_asym

        generic map(

          width  => RAMblock_maxwidth,

          depth  => depth,

          device => device

        )

        port map(

          clk => clk,

          -- write port

          waddr => waddr,

          we    => we_RAM(i),

          din   => modulus_in,

          -- read port

          raddr => modulus_sel,

          dout  => modulus_out((i+1)*RAMblock_maxwidth-1 downto i*RAMblock_maxwidth)

        );

        -- we

        process (write_modulus, modulus_addr)

        begin

          if modulus_addr(log2(width/32)-1 downto log2(RAMblock_maxwidth/32)) = conv_std_logic_vector(i,RAMselect_aw) then

            we_RAM(i) <= write_modulus;

          else

            we_RAM(i) <= '0';

          end if;

        end process;

      end generate; -- end of if generate for full blocks

      optional_part : if (i = nrRAMblocks_full) and (RAMblock_part /= 0) generate

        -- signals for optional part

        signal waddr_part : std_logic_vector(log2(RAMblock_part_width*depth/32)-1 downto 0);

        signal we_part    : std_logic;

      begin

        -- write port signal

        waddr_part <= modulus_in_sel & modulus_addr(log2(RAMblock_part_width/32)-1 downto 0);

        ramblock_part : dpramblock_asym

        generic map(

          width  => RAMblock_part_width,

          depth  => depth,

          device => device

        )

        port map(

          clk => clk,

          -- write port

          waddr => waddr_part,

          we    => we_part,

          din   => modulus_in,

          -- read port

          raddr => modulus_sel,

          dout  => modulus_out(width-1 downto i*RAMblock_maxwidth)

        );

        -- we_part

        process (write_modulus, modulus_addr)

        begin

          if modulus_addr(log2(width/32)-1 downto log2(RAMblock_maxwidth/32)) = conv_std_logic_vector(i,RAMselect_aw) then

            we_part <= write_modulus;

          else

            we_part <= '0';

          end if;

        end process;

      end generate;-- end of if generate for part block

    end generate;-- end of for generate

  end generate;-- end of if generate for multiple blocks

end structural;