Subversion Repositories mod_sim_exp

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----  modulus_ram_gen                                             ---- 

----                                                              ---- 

----  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                       ----

----                                                              ---- 

----  Dependencies:                                               ----

----    - dpram_generic                                           ----

----                                                              ----

----  Authors:                                                    ----

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

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

----                                                              ---- 

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----                                                              ---- 

---- 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                     ---- 

----                                                              ---- 

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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.mod_sim_exp_pkg.all;

use mod_sim_exp.std_functions.all;

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

-- adjustable width and depth(nr of moduluses)

entity modulus_ram_gen is

  generic(

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

    depth : integer := 2      -- nr of moduluses

  );

  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_gen;

architecture Behavioral of modulus_ram_gen is

  --- constants

  constant nrRAMs       : integer := width/32;

  constant RAMselect_aw : integer := log2(nrRAMs);

  constant RAMdepth_aw  : integer := log2(depth);

  constant total_aw     : integer := RAMdepth_aw+RAMselect_aw;

  -- interconnection signals

  signal modulus_rdaddr : std_logic_vector(RAMdepth_aw-1 downto 0);

  signal modulus_wraddr : std_logic_vector(total_aw-1 downto 0);

  signal we : std_logic_vector(nrRAMs-1 downto 0);

begin

        modulus_wraddr(RAMselect_aw-1 downto 0) <= modulus_addr;

        modulus_wraddr(total_aw-1 downto RAMselect_aw) <= modulus_in_sel;

        -- generate (width/32) blocks of 32-bit ram with a given depth

        -- these rams outputs are concatenated to a width-bit signal

  ramblocks : for i in 0 to nrRAMs-1 generate

    ramblock: dpram_generic

    generic map(

      depth => depth

    )

    port map(

      clk => clk,

      -- write port

      waddr => modulus_wraddr(total_aw-1 downto RAMselect_aw),

      we    => we(i),

      din   => modulus_in,

      -- read port

      raddr => modulus_rdaddr,

      dout  => modulus_out(((i+1)*32)-1 downto i*32)

    );

    -- connect the w

    process (write_modulus, modulus_wraddr)

    begin

      if modulus_wraddr(RAMselect_aw-1 downto 0) = conv_std_logic_vector(i,RAMselect_aw) then

        we(i) <= write_modulus;

      else

        we(i) <= '0';

      end if;

    end process;

  end generate;

  modulus_rdaddr <= modulus_sel;

end Behavioral;