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-- $Id: ibdr_lp11.vhd 641 2015-02-01 22:12:15Z mueller $

--

-- Copyright 2009-2013 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:    ibdr_lp11 - syn

-- Description:    ibus dev(rem): LP11

--

-- 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    12   35    0   24 s  5.6

-- 2009-07-11   232 10.1.03 K39  xc3s1000-4    11   30    0   19 s  5.8

--

-- Revision History: 

-- Date         Rev Version  Comment

-- 2013-05-04   515   1.3    BUGFIX: r.err was cleared in racc read !

-- 2011-11-18   427   1.2.2  now numeric_std clean

-- 2010-10-23   335   1.2.1  rename RRI_LAM->RB_LAM;

-- 2010-10-17   333   1.2    use ibus V2 interface

-- 2010-06-11   303   1.1    use IB_MREQ.racc instead of RRI_REQ

-- 2009-06-21   228   1.0.1  generate interrupt locally when err=1

-- 2009-05-30   220   1.0    Initial version 

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

--

-- Notes:

--   - the ERR bit is just a status flag

--   - no hardware interlock (DONE forced 0 when ERR=1), like in simh

--   - also no interrupt when ERR goes 1, like in simh

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

use work.slvtypes.all;

use work.iblib.all;

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

entity ibdr_lp11 is                     -- ibus dev(rem): LP11

                                        -- fixed address: 177514

  port (

    CLK : in slbit;                     -- clock

    RESET : in slbit;                   -- system reset

    BRESET : in slbit;                  -- ibus reset

    RB_LAM : out slbit;                 -- remote attention

    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 ibdr_lp11;

architecture syn of ibdr_lp11 is

  constant ibaddr_lp11 : slv16 := slv(to_unsigned(8#177514#,16));

  constant ibaddr_csr : slv1 := "0";   -- csr address offset

  constant ibaddr_buf : slv1 := "1";   -- buf address offset

  constant csr_ibf_err :   integer := 15;

  constant csr_ibf_done :  integer :=  7;

  constant csr_ibf_ie :    integer :=  6;

  constant buf_ibf_val :   integer :=  8;

  type regs_type is record              -- state registers

    ibsel : slbit;                      -- ibus select

    err : slbit;                        -- csr: error flag

    done : slbit;                       -- csr: done flag

    ie : slbit;                         -- csr: interrupt enable

    buf : slv7;                         -- buf:

    intreq : slbit;                     -- interrupt request

  end record regs_type;

  constant regs_init : regs_type := (

    '0',                                -- ibsel

    '1',                                -- err  !! is set !!

    '1',                                -- done !! is set !!

    '0',                                -- ie

    (others=>'0'),                      -- buf

    '0'                                 -- intreq

  );

  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.err <= N_REGS.err;         -- don't reset ERR flag

        end if;

      else

        R_REGS <= N_REGS;

      end if;

    end if;

  end process proc_regs;

  proc_next : process (R_REGS, IB_MREQ, EI_ACK)

    variable r : regs_type := regs_init;

    variable n : regs_type := regs_init;

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

    variable ibreq : slbit := '0';

    variable ibrd : slbit := '0';

    variable ibw0 : slbit := '0';

    variable ibw1 : slbit := '0';

    variable ilam : slbit := '0';

  begin

    r := R_REGS;

    n := R_REGS;

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

    ibreq := IB_MREQ.re or IB_MREQ.we;

    ibrd  := IB_MREQ.re;

    ibw0  := IB_MREQ.we and IB_MREQ.be0;

    ibw1  := IB_MREQ.we and IB_MREQ.be1;

    ilam  := '0';

    -- ibus address decoder

    n.ibsel := '0';

    if IB_MREQ.aval='1' and

       IB_MREQ.addr(12 downto 2)=ibaddr_lp11(12 downto 2) then

      n.ibsel := '1';

    end if;

    -- ibus transactions

    if r.ibsel = '1' then

      case IB_MREQ.addr(1 downto 1) is

        when ibaddr_csr =>              -- CSR -- control status -------------

          idout(csr_ibf_err)  := r.err;

          idout(csr_ibf_done) := r.done;

          idout(csr_ibf_ie)   := r.ie;

          if IB_MREQ.racc = '0' then      -- cpu

            if ibw0 = '1' then

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

              if IB_MREQ.din(csr_ibf_ie) = '1' then

                if r.done='1' and r.ie='0' then   -- ie set while done=1

                  n.intreq := '1';                -- request interrupt

                end if;

              else

                n.intreq := '0';

              end if;

            end if;

          else                          -- rri

            if ibw1 = '1' then

              n.err := IB_MREQ.din(csr_ibf_err);

            end if;

          end if;

        when ibaddr_buf =>              -- BUF -- data buffer ----------------

          if IB_MREQ.racc = '0' then      -- cpu

            if ibw0 = '1' then

              n.buf    := IB_MREQ.din(n.buf'range);

              if r.err = '0' then         -- if online (handle via rbus)

                ilam     := '1';            -- request attention

                n.done   := '0';            -- clear done

                n.intreq := '0';            -- clear interrupt

              else                        -- if offline (discard locally)

                n.done   := '1';            -- set done

                if r.ie = '1' then          -- if interrupts enabled

                  n.intreq := '1';            -- request interrupt

                end if;

              end if;

            end if;

          else                          -- rri

            idout(r.buf'range)  := r.buf;

            idout(buf_ibf_val)  := not r.done;

            if ibrd = '1' then

              n.done := '1';

              if r.ie = '1' then

                n.intreq := '1';

              end if;

            end if;

          end if;

        when others => null;

      end case;

    end if;

    -- other state changes

    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';

    RB_LAM <= ilam;

    EI_REQ <= r.intreq;

  end process proc_next;

end syn;