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-- $Id: ibd_kw11l.vhd 676 2015-05-09 16:31:54Z mueller $

--

-- Copyright 2008-2015 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:    ibd_kw11l - syn

-- Description:    ibus dev(loc): KW11-L (line clock)

--

-- Dependencies:   -

-- Test bench:     -

-- Target Devices: generic

-- Tool versions:  ise 8.2-14.7; viv 2014.4; ghdl 0.18-0.31

--

-- Synthesized (xst):

-- Date         Rev  ise         Target      flop lutl lutm slic t peri

-- 2010-10-17   333 12.1    M53d xc3s1000-4     9   23    0   14 s  5.3

-- 2009-07-11   232 10.1.03 K39  xc3s1000-4     8   25    0   15 s  5.3

--

-- Revision History: 

-- Date         Rev Version  Comment

-- 2015-05-09   676   1.2    add CPUSUSP, freeze timer when cpu suspended

-- 2011-11-18   427   1.1.1  now numeric_std clean

-- 2010-10-17   333   1.1    use ibus V2 interface

-- 2009-06-01   221   1.0.5  BUGFIX: add RESET; don't clear tcnt on ibus reset

-- 2008-08-22   161   1.0.4  use iblib; add EI_ACK to proc_next sens. list

-- 2008-05-09   144   1.0.3  use intreq flop, use EI_ACK

-- 2008-01-20   112   1.0.2  fix proc_next sensitivity list; use BRESET

-- 2008-01-06   111   1.0.1  Renamed to ibd_kw11l (RRI_REQ not used)

-- 2008-01-05   110   1.0    Initial version 

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

use work.slvtypes.all;

use work.iblib.all;

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

entity ibd_kw11l is                     -- ibus dev(loc): KW11-L (line clock)

                                        -- fixed address: 177546

  port (

    CLK : in slbit;                     -- clock

    CE_MSEC : in slbit;                 -- msec pulse

    RESET : in slbit;                   -- system reset

    BRESET : in slbit;                  -- ibus reset

    CPUSUSP : in slbit;                 -- cpu suspended

    IB_MREQ : in ib_mreq_type;          -- ibus request

    IB_SRES : out ib_sres_type;         -- ibus response

    EI_REQ : out slbit;                 -- interrupt request

    EI_ACK : in slbit                   -- interrupt acknowledge

  );

end ibd_kw11l;

architecture syn of ibd_kw11l is

  constant ibaddr_kw11l : slv16 := slv(to_unsigned(8#177546#,16));

  constant lks_ibf_ie :   integer :=  6;

  constant lks_ibf_moni : integer :=  7;

  constant twidth : natural  :=  5;

  constant tdivide : natural := 20;

  type regs_type is record              -- state registers

    ibsel : slbit;                      -- ibus select    

    ie : slbit;                         -- interrupt enable

    moni : slbit;                       -- monitor bit

    intreq : slbit;                     -- interrupt request

    tcnt : slv(twidth-1 downto 0);      -- timer counter

  end record regs_type;

  constant regs_init : regs_type := (

    '0',                                -- ibsel

    '0',                                -- ie

    '1',                                -- moni (set on reset !!)

    '0',                                -- intreq

    (others=>'0')                       -- tcnt

  );

  signal R_REGS : regs_type := regs_init;

  signal N_REGS : regs_type := regs_init;

begin

  proc_regs: process (CLK)

  begin

    if rising_edge(CLK) then

      if BRESET = '1' then             -- BRESET is 1 for system and ibus reset

        R_REGS <= regs_init;

        if RESET = '0' then               -- if RESET=0 we do just an ibus reset

          R_REGS.tcnt <= N_REGS.tcnt;       -- don't clear msec tick counter

        end if;

      else

        R_REGS <= N_REGS;

      end if;

    end if;

  end process proc_regs;

  proc_next : process (R_REGS, IB_MREQ, CE_MSEC, CPUSUSP, EI_ACK)

    variable r : regs_type := regs_init;

    variable n : regs_type := regs_init;

    variable idout : slv16 := (others=>'0');

    variable ibreq : slbit := '0';

    variable ibw0 : slbit := '0';

  begin

    r := R_REGS;

    n := R_REGS;

    idout := (others=>'0');

    ibreq := IB_MREQ.re or IB_MREQ.we;

    ibw0  := IB_MREQ.we and IB_MREQ.be0;

    -- ibus address decoder

    n.ibsel := '0';

    if IB_MREQ.aval='1' and

       IB_MREQ.addr=ibaddr_kw11l(12 downto 1) then

      n.ibsel := '1';

    end if;

    -- ibus output driver

    if r.ibsel = '1' then

      idout(lks_ibf_ie)   := R_REGS.ie;

      idout(lks_ibf_moni) := R_REGS.moni;

    end if;

    -- ibus write transactions

    if r.ibsel='1' and ibw0='1' then

      n.ie   := IB_MREQ.din(lks_ibf_ie);

      n.moni := IB_MREQ.din(lks_ibf_moni);

      if IB_MREQ.din(lks_ibf_ie)='0' or IB_MREQ.din(lks_ibf_moni)='0' then

        n.intreq := '0';

      end if;

    end if;

    -- other state changes

    if CE_MSEC='1' and CPUSUSP='0' then     -- on msec and not suspended

      n.tcnt := slv(unsigned(r.tcnt) + 1);

      if unsigned(r.tcnt) = tdivide-1 then

        n.tcnt := (others=>'0');

        n.moni := '1';

        if r.ie = '1' then

          n.intreq := '1';

        end if;

      end if;

    end if;

    if EI_ACK = '1' then

      n.intreq := '0';

    end if;

    N_REGS <= n;

    IB_SRES.dout <= idout;

    IB_SRES.ack  <= r.ibsel and ibreq;

    IB_SRES.busy <= '0';

    EI_REQ <= r.intreq;

  end process proc_next;

end syn;