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-- $Id: iob_keeper_gen.vhd 314 2010-07-09 17:38:41Z mueller $

--

-- Copyright 2010- by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>

--

-- This program is free software; you may redistribute and/or modify it under

-- the terms of the GNU General Public License as published by the Free

-- Software Foundation, either version 2, or at your option any later version.

--

-- This program 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 complete details.

--

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

-- Module Name:    iob_keeper_gen - sim

-- Description:    keeper for IOB, vector

--

-- Dependencies:   -

-- Test bench:     -

-- Target Devices: generic Spartan, Virtex

-- Tool versions:  xst 8.1, 8.2, 9.1, 9.2; ghdl 0.18-0.25

-- Revision History: 

-- Date         Rev Version  Comment

-- 2010-06-03   299   1.1    add explicit R_KEEP and driver

-- 2008-05-22   148   1.0    Initial version 

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

library ieee;

use ieee.std_logic_1164.all;

use work.slvtypes.all;

use work.xlib.all;

entity iob_keeper_gen is                -- keeper for IOB, vector

  generic (

    DWIDTH : positive := 16);           -- data port width

  port (

    PAD  : inout slv(DWIDTH-1 downto 0)  -- i/o pad

  );

end iob_keeper_gen;

-- Is't possible to directly use 'PAD<='H' in proc_pad. Introduced R_KEEP and

-- the explicit driver 'PAD<=R_KEEP' to state the keeper function more clearly.

architecture sim of iob_keeper_gen is

  signal R_KEEP : slv(DWIDTH-1 downto 0) := (others=>'W');

begin

  proc_keep: process (PAD)

  begin

    for i in PAD'range loop

      if PAD(i) = '1' then

        R_KEEP(i) <= 'H';

      elsif PAD(i) = '0' then

        R_KEEP(i) <= 'L';

      elsif PAD(i)='X' or PAD(i)='U' then

        R_KEEP(i) <= 'W';

      end if;

    end loop;

    PAD <= R_KEEP;

  end process proc_keep;

end sim;