pps_ei.vhd

这是一个基于mips-I结构的处理器,32bit,冯诺依曼结构

------------------------------------------------------------------------------------
--                                                                                --
--    Copyright (c) 2004, Hangouet Samuel                                         --
--                  , Jan Sebastien                                               --
--                  , Mouton Louis-Marie                                          --
--                  , Schneider Olivier     all rights reserved                   --
--                                                                                --
--    This file is part of miniMIPS.                                              --
--                                                                                --
--    miniMIPS is free software; you can redistribute it and/or modify            --
--    it under the terms of the GNU General Public License as published by        --
--    the Free Software Foundation; either version 2 of the License, or           --
--    (at your option) any later version.                                         --
--                                                                                --
--    miniMIPS 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 General Public License for more details.                                --
--                                                                                --
--    You should have received a copy of the GNU General Public License           --
--    along with miniMIPS; if not, write to the Free Software                     --
--    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA   --
--                                                                                --
------------------------------------------------------------------------------------


-- If you encountered any problem, please contact :
--
--   [e-mail]
--   [e-mail]
--   [e-mail]
--



--------------------------------------------------------------------------
--                                                                      --
--                                                                      --
--        miniMIPS Processor : Instruction extraction stage             --
--                                                                      --
--                                                                      --
--                                                                      --
-- Authors : Hangouet  Samuel                                           --
--           Jan       S閎astien                                        --
--           Mouton    Louis-Marie                                      --
--           Schneider Olivier                                          --
--                                                                      --
--                                                          june 2003   --
--------------------------------------------------------------------------

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;

library work;
use work.pack_mips.all;

entity pps_ei is
port (
  clock : in std_logic;
  reset : in std_logic;
  clear : in std_logic;    -- Clear the pipeline stage
  stop_all : in std_logic; -- Evolution locking signal
  
  -- Asynchronous inputs
  stop_ei : in std_logic;  -- Lock the EI_adr and Ei_instr registers
  genop : in std_logic;    -- Send nops

  -- Bus controler interface
  CTE_instr : in bus32;    -- Instruction from the memory
  ETC_adr : out bus32;     -- Address to read in memory

  -- Synchronous inputs from PF stage
  PF_pc : in bus32;        -- Current value of the pc

  -- Synchronous outputs to DI stage
  EI_instr : out bus32;    -- Read interface
  EI_adr : out bus32;      -- Address from the read instruction
  EI_it_ok : out std_logic -- Allow hardware interruptions
);
end pps_ei;

architecture rtl of pps_ei is
begin

  ETC_adr <= PF_pc; -- Connexion of the PC to the memory address bus

  -- Set the results
  process (clock)
  begin
    if (clock='1' and clock'event) then
      if reset='1' then
        EI_instr <= INS_NOP;
        EI_adr <= (others => '0');
        EI_it_ok <= '0';
      elsif stop_all='0' then
        if clear='1' then
          -- Clear the stage
          EI_instr <= INS_NOP;
          EI_it_ok <= '0';
        elsif genop='1' and stop_ei='0' then
          -- Send a nop
          EI_instr <= INS_NOP;
          EI_it_ok <= '1';
        elsif stop_ei='0' then
          -- Normal evolution
          EI_adr <= PF_pc;
          EI_instr <= CTE_instr;
          EI_it_ok <= '1';
        end if;
      end if;
    end if;
  end process;
end rtl;