Subversion Repositories t400

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

--

-- The G port controller.

--

-- $Id: t400_io_g.vhd 179 2009-04-01 19:48:38Z arniml $

--

-- 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_opt_pack.all;

use work.t400_pack.all;

entity t400_io_g is

  generic (

    opt_out_type_3_g : integer := t400_opt_out_type_std_c;

    opt_out_type_2_g : integer := t400_opt_out_type_std_c;

    opt_out_type_1_g : integer := t400_opt_out_type_std_c;

    opt_out_type_0_g : integer := t400_opt_out_type_std_c;

    opt_microbus_g   : integer := t400_opt_no_microbus_c

  );

  port (

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

    ck_i       : in  std_logic;

    ck_en_i    : in  boolean;

    por_i      : in  boolean;

    res_i      : in  boolean;

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

    op_i       : in  io_g_op_t;

    m_i        : in  dw_t;

    dec_data_i : in  dec_data_t;

    cs_n_i     : in  std_logic;

    wr_n_i     : in  std_logic;

    -- Port G Interface -------------------------------------------------------

    io_g_o     : out dw_t;

    io_g_en_o  : out dw_t

  );

end t400_io_g;

use work.t400_io_pack.all;

architecture rtl of t400_io_g is

  signal g_q   : dw_t;

  signal vdd_s : std_logic;

begin

  vdd_s <= '1';

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

  -- Process g_reg

  --

  -- Purpose:

  --   Implements the G output register.

  --

  g_reg: process (ck_i, por_i)

  begin

    if por_i then

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

    elsif ck_i'event and ck_i = '1' then

      if    res_i then

        -- synchronous reset upon external reset event

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

      elsif ck_en_i then

        case op_i is

          when IOG_LOAD_M =>

            g_q <= m_i;

          when IOG_LOAD_DEC =>

            g_q <= dec_data_i(dw_range_t);

          when others =>

            null;

        end case;

      end if;

      -- reset G(0) in MICROBUS operation upon write

      if opt_microbus_g = t400_opt_microbus_c and

         cs_n_i = '0' and wr_n_i = '0' then

        g_q(0) <= '0';

      end if;

    end if;

  end process g_reg;

  --

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

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

  -- Process out_driver

  --

  -- Purpose:

  --   Implements the output driver data and enable.

  --

  out_driver: process (g_q,

                       vdd_s)

  begin

    -- bit 3

    io_g_o(3)    <= io_out_f(dat => g_q(3),

                             opt => opt_out_type_3_g);

    io_g_en_o(3) <= io_en_f (en  => vdd_s, dat => g_q(3),

                             opt => opt_out_type_3_g);

     -- bit 2

    io_g_o(2)    <= io_out_f(dat => g_q(2),

                             opt => opt_out_type_2_g);

    io_g_en_o(2) <= io_en_f (en  => vdd_s, dat => g_q(2),

                             opt => opt_out_type_2_g);

    -- bit 1

    io_g_o(1)    <= io_out_f(dat => g_q(1),

                             opt => opt_out_type_1_g);

    io_g_en_o(1) <= io_en_f (en  => vdd_s, dat => g_q(1),

                             opt => opt_out_type_1_g);

    -- bit 0

    io_g_o(0)    <= io_out_f(dat => g_q(0),

                             opt => opt_out_type_0_g);

    io_g_en_o(0) <= io_en_f (en  => vdd_s, dat => g_q(0),

                             opt => opt_out_type_0_g);

  end process out_driver;

  --

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

end rtl;