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[/] [t400/] [trunk/] [rtl/] [vhdl/] [t400_pmem_ctrl.vhd] - Blame information for rev 176

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1 2 arniml
------------------------------------------------------------------------------
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--
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-- The Program memory controller.
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--
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-- $Id: t400_pmem_ctrl.vhd,v 1.3 2006-05-28 15:32:40 arniml Exp $
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--
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-- Copyright (c) 2006 Arnim Laeuger (arniml@opencores.org)
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--
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-- All rights reserved
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--
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-- Redistribution and use in source and synthezised forms, with or without
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-- modification, are permitted provided that the following conditions are met:
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--
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-- Redistributions of source code must retain the above copyright notice,
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-- this list of conditions and the following disclaimer.
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--
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-- Redistributions in synthesized form must reproduce the above copyright
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-- notice, this list of conditions and the following disclaimer in the
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-- documentation and/or other materials provided with the distribution.
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--
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-- Neither the name of the author nor the names of other contributors may
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-- be used to endorse or promote products derived from this software without
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-- specific prior written permission.
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--
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-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
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-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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-- POSSIBILITY OF SUCH DAMAGE.
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--
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-- Please report bugs to the author, but before you do so, please
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-- make sure that this is not a derivative work and that
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-- you have the latest version of this file.
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--
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-- The latest version of this file can be found at:
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--      http://www.opencores.org/cvsweb.shtml/t400/
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--
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-------------------------------------------------------------------------------
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library ieee;
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use ieee.std_logic_1164.all;
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use work.t400_opt_pack.all;
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use work.t400_pack.all;
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entity t400_pmem_ctrl is
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  generic (
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    opt_type_g : integer := t400_opt_type_420_c
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  );
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  port (
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    -- System Interface -------------------------------------------------------
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    ck_i       : in  std_logic;
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    ck_en_i    : in  boolean;
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    por_i      : in  boolean;
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    res_i      : in  boolean;
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    a_i        : in  dw_t;
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    m_i        : in  dw_t;
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    -- Control Interface ------------------------------------------------------
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    op_i       : in  pc_op_t;
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    dec_data_i : in  dec_data_t;
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    -- Stack Interface --------------------------------------------------------
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    pc_o       : out pc_t;
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    pc_i       : in  pc_t;
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    -- Program Memory Interface -----------------------------------------------
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    pm_addr_o  : out pc_t
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  );
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end t400_pmem_ctrl;
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library ieee;
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use ieee.numeric_std.all;
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-- pragma translate_off
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use work.tb_pack.tb_pc_s;
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-- pragma translate_on
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architecture rtl of t400_pmem_ctrl is
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  signal pc_q      : pc_t;
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  signal last_pc_s : pc_t;
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begin
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  -----------------------------------------------------------------------------
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  -- Determine last program counter address
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  -----------------------------------------------------------------------------
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  last_pc_s <=   to_unsigned(16#1ff#, pc_t'length)
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               when opt_type_g = t400_opt_type_410_c else
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                 to_unsigned(16#3ff#, pc_t'length);
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  -----------------------------------------------------------------------------
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  -- Process pc
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  --
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  -- Purpose:
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  --   Implements the program counter.
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  --
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  pc: process (ck_i, por_i)
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  begin
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    if por_i then
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      pc_q <= (others => '0');
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    elsif ck_i'event and ck_i = '1' then
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      if    res_i then
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        -- synchronous reset upon external reset event
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        pc_q                 <= (others => '0');
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      elsif ck_en_i then
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        -- determine PC update mode
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        case op_i is
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          -- increment program counter ----------------------------------------
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          when PC_INC_PC =>
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            if pc_q = last_pc_s then
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              -- roll over
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              pc_q           <= (others => '0');
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            else
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              pc_q           <= pc_q + 1;
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            end if;
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          -- Load lower 6 bits from program memory data -----------------------
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          when PC_LOAD_6 =>
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            pc_q(5 downto 0) <= unsigned(dec_data_i(5 downto 0));
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          -- Load lower 7 bits from program memory data -----------------------
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          when PC_LOAD_7 =>
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            pc_q(6 downto 0) <= unsigned(dec_data_i(6 downto 0));
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          -- Load lower 8 bits from program memory data -----------------------
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          when PC_LOAD_8 =>
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            pc_q(7 downto 0) <= unsigned(dec_data_i(7 downto 0));
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          -- Load all bits from program memory data ---------------------------
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          when PC_LOAD =>
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            pc_q             <= unsigned(dec_data_i);
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          -- pop program counter from stack -----------------------------------
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          when PC_POP =>
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            pc_q             <= pc_i;
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          -- update program counter for LQID instruction ----------------------
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          when PC_LOAD_A_M =>
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            pc_q(7 downto 4) <= unsigned(a_i);
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            pc_q(3 downto 0) <= unsigned(m_i);
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          -- load interrupt vector --------------------------------------------
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          when PC_INT =>
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            if opt_type_g = t400_opt_type_420_c then
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              -- load address 0x100, i.e. skip first instruction at
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              -- vector address 0x0ff which has to be a NOP :-)
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              pc_q <= (8 => '1', others => '0');
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            end if;
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          when others =>
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            null;
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        end case;
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      end if;
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    end if;
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  end process pc;
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  --
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  -----------------------------------------------------------------------------
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  -- pragma translate_off
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  -- instrument interrupt testbench
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  tb_pc_s <= pc_q;
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  -- pragma translate_on
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  -----------------------------------------------------------------------------
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  -- Output mapping
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  -----------------------------------------------------------------------------
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  pc_o      <= pc_q;
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  pm_addr_o <= pc_q;
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end rtl;
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-------------------------------------------------------------------------------
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-- File History:
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--
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-- $Log: not supported by cvs2svn $
190 89 arniml
-- Revision 1.2  2006/05/27 19:16:52  arniml
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-- interrupt functionality added
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--
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-- Revision 1.1.1.1  2006/05/06 01:56:45  arniml
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-- import from local CVS repository, LOC_CVS_0_1
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--
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-------------------------------------------------------------------------------

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