Subversion Repositories mod_sim_exp

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

----  mont_ctrl                                                   ---- 

----                                                              ---- 

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

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

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

----                                                              ---- 

----  Description                                                 ---- 

----    control unit for a pipelined montgomery multiplier, with  ----

----    split pipeline operation and "auto-run" support           ----

----                                                              ----

----  Dependencies:                                               ----

----    - autorun_cntrl                                           ----

----                                                              ----

----  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;

-- This module controls the montgommery mutliplier and controls traffic between

-- RAM and multiplier. Also contains the autorun logic for exponentiations.

entity mont_ctrl is

  port (

    clk   : in std_logic;

    reset : in std_logic;

      -- bus side

    start           : in std_logic;

    x_sel_single    : in std_logic_vector(1 downto 0);

    y_sel_single    : in std_logic_vector(1 downto 0);

    run_auto        : in std_logic;

    op_buffer_empty : in std_logic;

    op_sel_buffer   : in std_logic_vector(31 downto 0);

    read_buffer     : out std_logic;

    buffer_noread   : in std_logic;

    done            : out std_logic;

    calc_time       : out std_logic;

      -- multiplier side

    op_sel           : out std_logic_vector(1 downto 0);

    load_x           : out std_logic;

    load_result      : out std_logic;

    start_multiplier : out std_logic;

    multiplier_ready : in std_logic

  );

end mont_ctrl;

architecture Behavioral of mont_ctrl is

  signal start_d      : std_logic; -- delayed version of start input

  signal start_pulse        : std_logic;

  signal auto_start_pulse   : std_logic;

  signal start_multiplier_i   : std_logic;

  signal start_up_counter   : std_logic_vector(2 downto 0) := "100"; -- used in op_sel at multiplier start

  signal calc_time_i : std_logic; -- high ('1') during multiplication

  signal x_sel        : std_logic_vector(1 downto 0); -- the operand used as x input

  signal y_sel        : std_logic_vector(1 downto 0); -- the operand used as y input

  signal x_sel_buffer : std_logic_vector(1 downto 0); -- x operand as specified by fifo buffer (autorun)

  signal auto_done             : std_logic;

  signal start_auto            : std_logic;

  signal auto_multiplier_done_i : std_logic;

begin

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

        -- Processes related to starting and stopping the multiplier

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

        -- generate a start pulse (duration 1 clock cycle) based on ext. start sig

        START_PULSE_PROC: process(clk)

        begin

                if rising_edge(clk) then

                        start_d <= start;

                end if;

        end process START_PULSE_PROC;

        start_pulse <= start and (not start_d);

        start_auto <= start_pulse and run_auto;

        -- to start the multiplier we first need to select the x_operand and

        -- clock it in the x shift register

        -- the we select the y_operand and start the multiplier

        -- start_up_counter

        --   default state : "100"

        --   at start pulse counter resets to 0 and counts up to "100"

        START_MULT_PROC: process(clk, reset)

        begin

                if reset = '1' then

                        start_up_counter <= "100";

                elsif rising_edge(clk) then

                        if start_pulse = '1' or auto_start_pulse = '1' then

                                start_up_counter <= "000";

                        elsif start_up_counter(2) /= '1' then

                                start_up_counter <= start_up_counter + '1';

                        else

                                start_up_counter <= "100";

                        end if;

                else

                        start_up_counter <= start_up_counter;

                end if;

        end process;

        -- select operands (autorun/single run)

        x_sel <= x_sel_buffer when (run_auto = '1') else x_sel_single;

        y_sel <= "11" when (run_auto = '1') else y_sel_single; -- y is operand3 in auto mode

        -- clock operands to operand_mem output (first x, then y)

        with start_up_counter(2 downto 1) select

                op_sel <= x_sel when "00",  -- start_up_counter="00x" (first 2 cycles)

                          y_sel when others;  -- 

        load_x <= start_up_counter(0) and (not start_up_counter(1)); -- latch x operand if start_up_counter="x01"

        -- start multiplier when start_up_counter="x11"

        start_multiplier_i <= start_up_counter(1) and start_up_counter(0);

        start_multiplier <= start_multiplier_i;

        -- signal calc time is high during multiplication

        CALC_TIME_PROC: process(clk, reset)

        begin

                if reset = '1' then

                        calc_time_i <= '0';

                elsif rising_edge(clk) then

                        if start_multiplier_i = '1' then

                                calc_time_i <= '1';

                        elsif multiplier_ready = '1' then

                                calc_time_i <= '0';

                        else

                                calc_time_i <= calc_time_i;

                        end if;

                else

                        calc_time_i <= calc_time_i;

                end if;

        end process CALC_TIME_PROC;

        calc_time <= calc_time_i;

        -- what happens when a multiplication has finished

        load_result <= multiplier_ready;

        -- ignore multiplier_ready when in automode, the logic will assert auto_done when finished

        done <= ((not run_auto) and multiplier_ready) or auto_done;

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

        -- Processes related to op_buffer cntrl and auto_run mode

        -- start_auto     -> start autorun mode operation

        -- auto_start_pulse <- autorun logic starts the multiplier

        -- auto_done        <- autorun logic signals when autorun operation has finished

        -- x_sel_buffer   <- autorun logic determines which operand is used as x

        -- check buffer empty signal

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

        -- multiplier_ready is only passed to autorun control when in autorun mode

        auto_multiplier_done_i <= (multiplier_ready and run_auto);

  autorun_control_logic : autorun_cntrl port map(

    clk              => clk,

    reset            => reset,

    start            => start_auto,

    done             => auto_done,

    op_sel           => x_sel_buffer,

    start_multiplier => auto_start_pulse,

    multiplier_done  => auto_multiplier_done_i,

    read_buffer      => read_buffer,

    buffer_din       => op_sel_buffer,

    buffer_empty     => op_buffer_empty

  );

end Behavioral;