Subversion Repositories t48

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

--

-- The Interrupt Controller.

-- It collects the interrupt sources and notifies the decoder.

--

-- $Id: int.vhd,v 1.6 2005-11-01 21:26:24 arniml Exp $

--

-- Copyright (c) 2004, Arnim Laeuger (arniml@opencores.org)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/cvsweb.shtml/t48/

--

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

library ieee;

use ieee.std_logic_1164.all;

use work.t48_pack.mstate_t;

entity t48_int is

  port (

    clk_i             : in  std_logic;

    res_i             : in  std_logic;

    en_clk_i          : in  boolean;

    xtal_i            : in  std_logic;

    clk_mstate_i      : in  mstate_t;

    jtf_executed_i    : in  boolean;

    tim_overflow_i    : in  boolean;

    tf_o              : out std_logic;

    en_tcnti_i        : in  boolean;

    dis_tcnti_i       : in  boolean;

    int_n_i           : in  std_logic;

    ale_i             : in  boolean;

    last_cycle_i      : in  boolean;

    en_i_i            : in  boolean;

    dis_i_i           : in  boolean;

    ext_int_o         : out boolean;

    tim_int_o         : out boolean;

    retr_executed_i   : in  boolean;

    int_executed_i    : in  boolean;

    int_pending_o     : out boolean;

    int_in_progress_o : out boolean

  );

end t48_int;

use work.t48_pack.all;

architecture rtl of t48_int is

  constant tim_int_c : std_logic := '0';

  constant ext_int_c : std_logic := '1';

  type int_state_t is (IDLE, PENDING, INT);

  signal int_state_s,

         int_state_q  : int_state_t;

  signal timer_flag_q       : boolean;

  signal timer_overflow_q   : boolean;

  signal timer_int_enable_q : boolean;

  signal int_q              : boolean;

  signal int_enable_q       : boolean;

  signal ale_q              : boolean;

  signal int_type_q         : std_logic;

  signal int_in_progress_q  : boolean;

begin

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

  -- Process nstate

  --

  -- Purpose:

  --   Determines the next state of the Interrupt controller FSM.

  --

  nstate: process (int_state_q,

                   int_type_q,

                   int_in_progress_q,

                   int_executed_i,

                   retr_executed_i,

                   clk_mstate_i,

                   last_cycle_i)

  begin

    int_state_s <= int_state_q;

    case int_state_q is

      when IDLE =>

        if int_in_progress_q and

           last_cycle_i and clk_mstate_i = MSTATE5 then

          int_state_s <= PENDING;

        end if;

      when PENDING =>

        if int_executed_i then

          int_state_s <= INT;

        end if;

      when INT =>

        if retr_executed_i then

          int_state_s <= IDLE;

        end if;

      when others =>

        int_state_s <= IDLE;

    end case;

  end process nstate;

  --

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

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

  -- Process regs

  --

  -- Purpose:

  --   Implement the various registers.

  --   They are designed according Figure "Interrupt Logic" of

  --   "The Single Component MCS-48 System".

  --

  regs: process (res_i, clk_i)

  begin

    if res_i = res_active_c then

      timer_flag_q       <= false;

      timer_overflow_q   <= false;

      timer_int_enable_q <= false;

      int_enable_q       <= false;

      int_type_q         <= '0';

      int_state_q        <= IDLE;

      int_in_progress_q  <= false;

    elsif clk_i'event and clk_i = clk_active_c then

      if en_clk_i then

        int_state_q <= int_state_s;

        if jtf_executed_i then

          timer_flag_q <= false;

        elsif tim_overflow_i then

          timer_flag_q <= true;

        end if;

        if (int_type_q = tim_int_c and int_executed_i) or

          not timer_int_enable_q then

          timer_overflow_q <= false;

        elsif tim_overflow_i then

          timer_overflow_q <= true;

        end if;

        if dis_tcnti_i then

          timer_int_enable_q <= false;

        elsif en_tcnti_i then

          timer_int_enable_q <= true;

        end if;

        if dis_i_i then

          int_enable_q <= false;

        elsif en_i_i then

          int_enable_q <= true;

        end if;

        if retr_executed_i then

          int_in_progress_q <= false;

        elsif (int_q and int_enable_q) or

          timer_overflow_q then

          int_in_progress_q <= true;

          if not int_in_progress_q then

            int_type_q <= to_stdLogic(int_q and int_enable_q);

          end if;

        end if;

      end if;

    end if;

  end process regs;

  --

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

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

  -- Process xtal_regs

  --

  -- Purpose:

  --   Implements the sequential registers clocked with XTAL.

  --

  xtal_regs: process (res_i, xtal_i)

  begin

    if res_i = res_active_c then

      int_q <= false;

      ale_q <= false;

    elsif xtal_i'event and xtal_i = clk_active_c then

      ale_q       <= ale_i;

      if last_cycle_i and

        ale_q  and not ale_i  then

        int_q <= not to_boolean(int_n_i);

      end if;

    end if;

  end process xtal_regs;

  --

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

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

  -- Output Mapping.

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

  tf_o              <= to_stdLogic(timer_flag_q);

  ext_int_o         <= int_type_q = ext_int_c;

  tim_int_o         <= int_type_q = tim_int_c;

  int_pending_o     <= int_state_q = PENDING;

  int_in_progress_o <= int_in_progress_q and int_state_q /= IDLE;

end rtl;

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

-- File History:

--

-- $Log: not supported by cvs2svn $

-- Revision 1.5  2005/09/13 21:00:16  arniml

-- Fix bug reports:

-- "Target address of JMP to Program Memory Bank 1 corrupted by interrupt"

-- "Return address of CALL to Program Memory Bank 1 corrupted by interrupt"

-- int_in_progress_o was active one cycle before int_pending_o is

-- asserted. this confused the mb multiplexer which determines the state of

-- the memory bank selection flag

--

-- Revision 1.4  2005/06/11 10:08:43  arniml

-- introduce prefix 't48_' for all packages, entities and configurations

--

-- Revision 1.3  2004/07/11 16:51:33  arniml

-- cleanup copyright notice

--

-- Revision 1.2  2004/06/30 21:18:28  arniml

-- Fix bug report:

-- "Program Memory bank can be switched during interrupt"

-- int module emits int_in_progress signal that is used inside the decoder

-- to hold mb low for JMP and CALL during interrupts

--

-- Revision 1.1  2004/03/23 21:31:52  arniml

-- initial check-in

--

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