Subversion Repositories t400

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

--

-- The IN port controller.

--

-- $Id: t400_io_in.vhd,v 1.3 2006-05-27 19:14:18 arniml Exp $

--

-- Copyright (c) 2006 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/t400/

--

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

library ieee;

use ieee.std_logic_1164.all;

use work.t400_pack.all;

entity t400_io_in is

  port (

    -- System Interface -------------------------------------------------------

    ck_i      : in  std_logic;

    ck_en_i   : in  boolean;

    por_i     : in  boolean;

    icyc_en_i : in boolean;

    in_en_i   : in  boolean;

    -- Control Interface ------------------------------------------------------

    op_i      : in  io_in_op_t;

    en1_i     : in  std_logic;

    -- Port Interface ---------------------------------------------------------

    io_in_i   : in  dw_t;

    in_o      : out dw_t;

    int_o     : out boolean

  );

end t400_io_in;

architecture rtl of t400_io_in is

  constant idx_in3_c  : natural := 2;

  constant idx_in0_c  : natural := 1;

  constant idx_int_c  : natural := 0;

  type     neg_edge_t is array (natural range 1 downto 0) of

                           std_logic_vector(2 downto 0);

  signal   neg_edge_q : neg_edge_t;

  signal   neg_edge_s : std_logic_vector(2 downto 0);

  signal   il_q       : std_logic_vector(1 downto 0);

  signal   int_q,

           int_icyc_q : boolean;

begin

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

  -- Process seq

  --

  -- Purpose:

  --   Implements the sequential elements.

  --

  seq: process (ck_i, por_i)

    variable neg_edge_v : std_logic_vector(2 downto 0);

  begin

    if por_i then

      neg_edge_q <= (others => (others => '0'));

      il_q       <= (others => '0');

      int_q      <= false;

      int_icyc_q <= false;

    elsif ck_i'event and ck_i = '1' then

      -- negative edge detector filp-flops ------------------------------------

      neg_edge_v(idx_in3_c) := to_X01(io_in_i(3));

      neg_edge_v(idx_in0_c) := to_X01(io_in_i(0));

      neg_edge_v(idx_int_c) := to_X01(io_in_i(1));

      if in_en_i then

        neg_edge_q(0) <= neg_edge_v;

        neg_edge_q(1) <= neg_edge_q(0) or neg_edge_v;

      end if;

      -- IL latches -----------------------------------------------------------

      if in_en_i then

        if neg_edge_q(1)(idx_in3_c) = '1' and

           ((neg_edge_q(0)(idx_in3_c) or neg_edge_v(idx_in3_c)) = '0') then

          il_q(1) <= '1';

        end if;

        if neg_edge_q(1)(idx_in0_c) = '1' and

           ((neg_edge_q(0)(idx_in0_c) or neg_edge_v(idx_in0_c)) = '0') then

          il_q(0) <= '1';

        end if;

      end if;

      -- Interrupt trigger ----------------------------------------------------

      if in_en_i then

        if neg_edge_q(1)(idx_int_c) = '1' and

           ((neg_edge_q(0)(idx_int_c) or neg_edge_v(idx_int_c)) = '0') then

          int_q <= true;

        end if;

      end if;

      if icyc_en_i then

        -- delay interrupt request until end of current instruction

        -- this ensures that the interrupt is valid for a full instruction

        -- (i.e. the next one)

        int_icyc_q <= int_q;

      end if;

      if ck_en_i then

        if op_i = IOIN_INIL then

          il_q <= (others => '0');

        end if;

        if op_i = IOIN_INTACK then

          int_q      <= false;

          int_icyc_q <= false;

        end if;

      end if;

    end if;

  end process seq;

  --

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

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

  -- Output mapping

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

  in_o  <=   il_q(1) & "00" & il_q(0)

           when op_i = IOIN_INIL else

             io_in_i;

  int_o <= int_icyc_q;

end rtl;

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

-- File History:

--

-- $Log: not supported by cvs2svn $

-- Revision 1.2  2006/05/23 01:13:28  arniml

-- + reset neg_edge flip-flops to '1'

--   -> after por, a 1-to-0 edge is required to trigger the latches initially

-- + use to_X01

--

-- Revision 1.1  2006/05/22 00:00:55  arniml

-- initial check-in

--

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