Subversion Repositories t48

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--

-- Interface Timing Checker.

--

-- $Id: if_timing.vhd,v 1.1 2004-04-25 16:24:10 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;

entity if_timing is

  port (

    xtal_i   : in std_logic;

    ale_i    : in std_logic;

    psen_n_i : in std_logic;

    rd_n_i   : in std_logic;

    wr_n_i   : in std_logic;

    prog_n_i : in std_logic;

    db_bus_i : in std_logic_vector(7 downto 0);

    p2_i     : in std_logic_vector(7 downto 0)

  );

end if_timing;

architecture behav of if_timing is

  signal last_xtal_rise_s    : time;

  signal period_s            : time;

  signal last_ale_rise_s,

         last_ale_fall_s     : time;

  signal last_psen_n_rise_s,

         last_psen_n_fall_s  : time;

  signal last_rd_n_rise_s,

         last_rd_n_fall_s    : time;

  signal last_wr_n_rise_s,

         last_wr_n_fall_s    : time;

  signal last_prog_n_rise_s,

         last_prog_n_fall_s  : time;

  signal last_bus_change_s,

         bus_change_ale_s    : time;

  signal last_p2_change_s    : time;

  signal t_CY                : time;

begin

  t_CY <= 15 * period_s;

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

  -- Check RD

  --

  rd_check: process (rd_n_i)

  begin

    if rd_n_i'event then

      case rd_n_i is

        -- RD active

        when '0' =>

          -- tLAFC1: ALE to Control RD

          assert (now - last_ale_fall_s) > (t_CY / 5 - 75 ns)

            report "Timing violation of tLAFC1 on RD!"

            severity error;

          -- tAFC1: Addr Float to RD

          assert (now - last_bus_change_s) > (t_CY * 2/15 - 40 ns)

            report "Timing violation of tAFC1 on RD!"

            severity error;

        -- RD inactive

        when '1' =>

          -- tCC1: Control Pulse Width RD

          assert (now - last_rd_n_fall_s) > (t_CY / 2 - 200 ns)

            report "Timing violation of tCC1 on RD!"

            severity error;

        when others =>

          null;

      end case;

    end if;

  end process rd_check;

  --

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

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

  -- Check WR

  --

  wr_check: process (wr_n_i)

  begin

    if wr_n_i'event then

      case wr_n_i is

        -- WR active

        when '0' =>

          -- tLAFC1: ALE to Control WR

          assert (now - last_ale_fall_s) > (t_CY / 5 - 75 ns)

            report "Timing violation of tLAFC1 on WR!"

            severity error;

          -- tAW: Addr Setup to WR

          assert (now - bus_change_ale_s) > (t_CY / 3 - 150 ns)

            report "Timing violation of tAW on WR!"

            severity error;

          -- tAW sanity check

          assert (now - bus_change_ale_s) < t_CY

            report "Timing relation between BUS and WR inconsistent!"

            severity error;

        -- WR inactive

        when '1' =>

          -- tCC1: Control Pulse Width WR

          assert (now - last_wr_n_fall_s) > (t_CY / 2 - 200 ns)

            report "Timing violation of tCC1 on WR!"

            severity error;

          -- tDW: Data Setup before WR

          assert (now - last_bus_change_s) > (t_CY * 13/30 - 200 ns)

            report "Timing violation of tDW on WR!"

            severity error;

        when others =>

          null;

      end case;

    end if;

  end process wr_check;

  --

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

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

  -- Check BUS

  --

  bus_check: process (db_bus_i)

  begin

    if db_bus_i'event then

      -- RD access

      -- tAD1 and tRD1 are not checked as they are constraints for the

      -- external memory, not the t48!

      -- WR access

      if wr_n_i = '0' then

        -- tDW: Data Hold after WR

        assert (now - last_wr_n_rise_s) > (t_CY / 15 - 50 ns)

          report "Timing violation of tDW on BUS vs. WR!"

          severity error;

      end if;

    end if;

  end process bus_check;

  --

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

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

  -- Monitor XTAL

  --

  xtal_mon: process

  begin

    last_xtal_rise_s     <= 0 ns;

    period_s             <= 90 ns;

    while true loop

      wait on xtal_i;

      if xtal_i = '1' then

        period_s         <= now - last_xtal_rise_s;

        last_xtal_rise_s <= now;

      end if;

    end loop;

  end process xtal_mon;

  --

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

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

  -- Monitor ALE

  --

  ale_mon: process

  begin

    last_ale_rise_s       <= 0 ns;

    last_ale_fall_s       <= 0 ns;

    while true loop

      wait on ale_i;

      case ale_i is

        when '0' =>

          last_ale_fall_s <= now;

        when '1' =>

          last_ale_rise_s <= now;

        when others =>

          null;

      end case;

    end loop;

  end process ale_mon;

  --

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

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

  -- Monitor PSEN

  --

  psen_mon: process

  begin

    last_psen_n_rise_s       <= 0 ns;

    last_psen_n_fall_s       <= 0 ns;

    while true loop

      wait on psen_n_i;

      case psen_n_i is

        when '0' =>

          last_psen_n_fall_s <= now;

        when '1' =>

          last_psen_n_rise_s <= now;

        when others =>

          null;

      end case;

    end loop;

  end process psen_mon;

  --

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

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

  -- Monitor RD

  --

  rd_mon: process

  begin

    last_rd_n_rise_s       <= 0 ns;

    last_rd_n_fall_s       <= 0 ns;

    while true loop

      wait on rd_n_i;

      case rd_n_i is

        when '0' =>

          last_rd_n_fall_s <= now;

        when '1' =>

          last_rd_n_rise_s <= now;

        when others =>

          null;

      end case;

    end loop;

  end process rd_mon;

  --

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

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

  -- Monitor WR

  --

  wr_mon: process

  begin

    last_wr_n_rise_s       <= 0 ns;

    last_wr_n_fall_s       <= 0 ns;

    while true loop

      wait on wr_n_i;

      case wr_n_i is

        when '0' =>

          last_wr_n_fall_s <= now;

        when '1' =>

          last_wr_n_rise_s <= now;

        when others =>

          null;

      end case;

    end loop;

  end process wr_mon;

  --

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

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

  -- Monitor PROG

  --

  prog_mon: process

  begin

    last_prog_n_rise_s       <= 0 ns;

    last_prog_n_fall_s       <= 0 ns;

    while true loop

      wait on prog_n_i;

      case prog_n_i is

        when '0' =>

          last_prog_n_fall_s <= now;

        when '1' =>

          last_prog_n_rise_s <= now;

        when others =>

          null;

      end case;

    end loop;

  end process prog_mon;

  --

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

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

  -- Monitor BUS

  --

  bus_mon: process

  begin

    last_bus_change_s    <= 0 ns;

    bus_change_ale_s     <= 0 ns;

    while true loop

      wait on db_bus_i;

      last_bus_change_s  <= now;

      if ale_i = '1' then

        bus_change_ale_s <= now;

      end if;

    end loop;

  end process bus_mon;

  --

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

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

  -- Monitor P2

  --

  p2_mon: process

  begin

    last_p2_change_s   <= 0 ns;

    while true loop

      wait on p2_i;

      last_p2_change_s <= now;

    end loop;

  end process p2_mon;

  --

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

end behav;

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