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-- $Id: pdp11_mmu.vhd 314 2010-07-09 17:38:41Z mueller $

--

-- Copyright 2006-2010 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:    pdp11_mmu - syn

-- Description:    pdp11: mmu - memory management unit

--

-- Dependencies:   pdp11_mmu_sadr

--                 pdp11_mmu_ssr12

--                 ibus/ib_sres_or_3

--

-- Test bench:     tb/tb_pdp11_core (implicit)

-- Target Devices: generic

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

-- Revision History: 

-- Date         Rev Version  Comment

-- 2010-06-20   307   1.3.7  rename cpacc to cacc in mmu_cntl_type

-- 2009-05-30   220   1.3.6  final removal of snoopers (were already commented)

-- 2009-05-09   213   1.3.5  BUGFIX: tie inst_compl permanentely '0'

--                           BUGFIX: set ssr0 trap_mmu even when traps disabled

-- 2008-08-22   161   1.3.4  rename pdp11_ibres_ -> ib_sres_, ubf_ -> ibf_

-- 2008-04-27   139   1.3.3  allow ssr1/2 tracing even with mmu_ena=0

-- 2008-04-25   138   1.3.2  add BRESET port, clear ssr0/3 with BRESET

-- 2008-03-02   121   1.3.1  remove snoopers

-- 2008-02-24   119   1.3    return always mapped address in PADDRH; remove

--                           cpacc handling; PADDR generation now on _vmbox

-- 2008-01-05   110   1.2.1  rename _mmu_regs -> _mmu_sadr

--                           rename IB_MREQ(ena->req) SRES(sel->ack, hold->busy)

-- 2008-01-01   109   1.2    use pdp11_mmu_regs (rather than _regset)

-- 2007-12-31   108   1.1.1  remove SADR memory address mux (-> _mmu_regfile)

-- 2007-12-30   107   1.1    use IB_MREQ/IB_SRES interface now

-- 2007-06-14    56   1.0.1  Use slvtypes.all

-- 2007-05-12    26   1.0    Initial version 

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use work.slvtypes.all;

use work.iblib.all;

use work.pdp11.all;

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

entity pdp11_mmu is                     -- mmu - memory management unit

  port (

    CLK : in slbit;                     -- clock

    CRESET : in slbit;                  -- console reset

    BRESET : in slbit;                  -- ibus reset

    CNTL : in mmu_cntl_type;            -- control port

    VADDR : in slv16;                   -- virtual address

    MONI : in mmu_moni_type;            -- monitor port

    STAT : out mmu_stat_type;           -- status port

    PADDRH : out slv16;                 -- physical address (upper 16 bit)

    IB_MREQ: in ib_mreq_type;           -- ibus request

    IB_SRES: out ib_sres_type           -- ibus response

  );

end pdp11_mmu;

architecture syn of pdp11_mmu is

  constant ibaddr_ssr0 : slv16 := conv_std_logic_vector(8#177572#,16);

  constant ibaddr_ssr3 : slv16 := conv_std_logic_vector(8#172516#,16);

  constant ssr0_ibf_abo_nonres : integer := 15;

  constant ssr0_ibf_abo_length : integer := 14;

  constant ssr0_ibf_abo_rdonly : integer := 13;

  constant ssr0_ibf_trap_mmu : integer := 12;

  constant ssr0_ibf_ena_trap : integer := 9;

  constant ssr0_ibf_inst_compl : integer := 7;

  subtype  ssr0_ibf_seg_mode is integer range 6 downto 5;

  constant ssr0_ibf_dspace : integer := 4;

  subtype  ssr0_ibf_seg_num is integer range 3 downto 1;

  constant ssr0_ibf_ena_mmu : integer := 0;

  constant ssr3_ibf_ena_ubmap : integer := 5;

  constant ssr3_ibf_ena_22bit : integer := 4;

  constant ssr3_ibf_dspace_km : integer := 2;

  constant ssr3_ibf_dspace_sm : integer := 1;

  constant ssr3_ibf_dspace_um : integer := 0;

  signal IBSEL_SSR0 : slbit := '0';     -- ibus select SSR0

  signal IBSEL_SSR3 : slbit := '0';     -- ibus select SSR3

  signal R_SSR0 : mmu_ssr0_type := mmu_ssr0_init;

  signal N_SSR0 : mmu_ssr0_type := mmu_ssr0_init;

  signal R_SSR3 : mmu_ssr3_type := mmu_ssr3_init;

  signal ASN : slv4 := "0000";          -- augmented segment number (1+3 bit)

  signal AIB_WE : slbit := '0';         -- update AIB

  signal AIB_SETA : slbit := '0';       -- set A bit in access information bits

  signal AIB_SETW : slbit := '0';       -- set W bit in access information bits

  signal TRACE : slbit := '0';          -- enable tracing in ssr1/2

  signal DSPACE : slbit := '0';         -- use dspace

  signal IB_SRES_SADR  : ib_sres_type := ib_sres_init;

  signal IB_SRES_SSR12 : ib_sres_type := ib_sres_init;

  signal IB_SRES_SSR03 : ib_sres_type := ib_sres_init;

  signal SARSDR : sarsdr_type := sarsdr_init;

begin

  SADR : pdp11_mmu_sadr port map (

    CLK      => CLK,

    MODE     => CNTL.mode,

    ASN      => ASN,

    AIB_WE   => AIB_WE,

    AIB_SETA => AIB_SETA,

    AIB_SETW => AIB_SETW,

    SARSDR   => SARSDR,

    IB_MREQ  => IB_MREQ,

    IB_SRES  => IB_SRES_SADR);

  SSR12 : pdp11_mmu_ssr12 port map (

    CLK     => CLK,

    CRESET  => CRESET,

    TRACE   => TRACE,

    MONI    => MONI,

    IB_MREQ => IB_MREQ,

    IB_SRES => IB_SRES_SSR12);

  IB_SRES_OR : ib_sres_or_3

    port map (

      IB_SRES_1  => IB_SRES_SADR,

      IB_SRES_2  => IB_SRES_SSR12,

      IB_SRES_3  => IB_SRES_SSR03,

      IB_SRES_OR => IB_SRES);

  proc_ibsel: process (IB_MREQ)

    variable issr0 : slbit := '0';

    variable issr3 : slbit := '0';

  begin

    issr0 := '0';

    issr3 := '0';

    if IB_MREQ.req = '1' then

      if IB_MREQ.addr = ibaddr_ssr0(12 downto 1) then issr0 := '1'; end if;

      if IB_MREQ.addr = ibaddr_ssr3(12 downto 1) then issr3 := '1'; end if;

    end if;

    IBSEL_SSR0         <= issr0;

    IBSEL_SSR3         <= issr3;

    IB_SRES_SSR03.ack  <= issr0 or issr3;

    IB_SRES_SSR03.busy <= '0';

  end process proc_ibsel;

  proc_ibdout : process (IBSEL_SSR0, IBSEL_SSR3, R_SSR0, R_SSR3)

    variable ssr0out : slv16 := (others=>'0');

    variable ssr3out : slv16 := (others=>'0');

  begin

    ssr0out := (others=>'0');

    if IBSEL_SSR0 = '1' then

      ssr0out(ssr0_ibf_abo_nonres) := R_SSR0.abo_nonres;

      ssr0out(ssr0_ibf_abo_length) := R_SSR0.abo_length;

      ssr0out(ssr0_ibf_abo_rdonly) := R_SSR0.abo_rdonly;

      ssr0out(ssr0_ibf_trap_mmu)   := R_SSR0.trap_mmu;

      ssr0out(ssr0_ibf_ena_trap)   := R_SSR0.ena_trap;

      ssr0out(ssr0_ibf_inst_compl) := R_SSR0.inst_compl;

      ssr0out(ssr0_ibf_seg_mode)   := R_SSR0.seg_mode;

      ssr0out(ssr0_ibf_dspace)     := R_SSR0.dspace;

      ssr0out(ssr0_ibf_seg_num)    := R_SSR0.seg_num;

      ssr0out(ssr0_ibf_ena_mmu)    := R_SSR0.ena_mmu;

    end if;

    ssr3out := (others=>'0');

    if IBSEL_SSR3 = '1' then

      ssr3out(ssr3_ibf_ena_ubmap) := R_SSR3.ena_ubmap;

      ssr3out(ssr3_ibf_ena_22bit) := R_SSR3.ena_22bit;

      ssr3out(ssr3_ibf_dspace_km) := R_SSR3.dspace_km;

      ssr3out(ssr3_ibf_dspace_sm) := R_SSR3.dspace_sm;

      ssr3out(ssr3_ibf_dspace_um) := R_SSR3.dspace_um;

    end if;

    IB_SRES_SSR03.dout <= ssr0out or ssr3out;

  end process proc_ibdout;

  proc_ssr0 : process (CLK)

  begin

    if CLK'event and CLK='1' then

      if BRESET = '1' then

        R_SSR0 <= mmu_ssr0_init;

      else

        R_SSR0 <= N_SSR0;

      end if;

    end if;

  end process proc_ssr0;

  proc_ssr3 : process (CLK)

  begin

    if CLK'event and CLK='1' then

      if BRESET = '1' then

        R_SSR3 <= mmu_ssr3_init;

      elsif IB_MREQ.we='1' and IBSEL_SSR3='1' then

        if IB_MREQ.be0 = '1' then

          R_SSR3.ena_ubmap <= IB_MREQ.din(ssr3_ibf_ena_ubmap);

          R_SSR3.ena_22bit <= IB_MREQ.din(ssr3_ibf_ena_22bit);

          R_SSR3.dspace_km <= IB_MREQ.din(ssr3_ibf_dspace_km);

          R_SSR3.dspace_sm <= IB_MREQ.din(ssr3_ibf_dspace_sm);

          R_SSR3.dspace_um <= IB_MREQ.din(ssr3_ibf_dspace_um);

        end if;

      end if;

    end if;

  end process proc_ssr3;

  proc_paddr : process (R_SSR0, R_SSR3, CNTL, SARSDR, VADDR)

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

    variable dspace_ok : slbit := '0';

    variable dspace_en : slbit := '0';

    variable asf : slv3 := (others=>'0'); -- va: active segment field

    variable bn : slv7 := (others=>'0');  -- va: block number

    variable iasn : slv4 := (others=>'0');-- augmented segment number

  begin

    asf := VADDR(15 downto 13);

    bn := VADDR(12 downto 6);

    dspace_en := '0';

    case CNTL.mode is

      when "00" => dspace_en := R_SSR3.dspace_km;

      when "01" => dspace_en := R_SSR3.dspace_sm;

      when "11" => dspace_en := R_SSR3.dspace_um;

      when others => null;

    end case;

    dspace_ok := CNTL.dspace and dspace_en;

    iasn(3) := dspace_ok;

    iasn(2 downto 0) := asf;

    ipaddrh := unsigned("000000000"&bn) + unsigned(SARSDR.saf);

    DSPACE <= dspace_ok;

    ASN    <= iasn;

    PADDRH <= ipaddrh;

  end process proc_paddr;

  proc_nssr0 : process (R_SSR0, R_SSR3, IB_MREQ, IBSEL_SSR0, DSPACE,

                        CNTL, MONI, SARSDR, VADDR)

    variable nssr0 : mmu_ssr0_type := mmu_ssr0_init;

    variable asf : slv3 := (others=>'0');

    variable bn : slv7 := (others=>'0');

    variable abo_nonres : slbit := '0';

    variable abo_length : slbit := '0';

    variable abo_rdonly : slbit := '0';

    variable ssr_freeze : slbit := '0';

    variable doabort : slbit := '0';

    variable dotrap : slbit := '0';

    variable dotrace : slbit := '0';

  begin

    nssr0 := R_SSR0;

    AIB_WE   <= '0';

    AIB_SETA <= '0';

    AIB_SETW <= '0';

    ssr_freeze := R_SSR0.abo_nonres or R_SSR0.abo_length or R_SSR0.abo_rdonly;

    dotrace := not(CNTL.cacc or ssr_freeze);

    asf := VADDR(15 downto 13);

    bn := VADDR(12 downto 6);

    abo_nonres := '0';

    abo_length := '0';

    abo_rdonly := '0';

    doabort := '0';

    dotrap := '0';

    if SARSDR.ed = '0' then             -- ed=0: upward expansion

      if unsigned(bn) > unsigned(SARSDR.slf) then

        abo_length := '1';

      end if;

    else                                -- ed=0: downward expansion

      if unsigned(bn) < unsigned(SARSDR.slf) then

        abo_length := '1';

      end if;

    end if;

    case SARSDR.acf is                  -- evaluate accecc control field

      when "000" =>                     -- segment non-resident

        abo_nonres := '1';

      when "001" =>                     -- read-only; trap on read

        if CNTL.wacc='1' or CNTL.macc='1' then

          abo_rdonly := '1';

        end if;

        dotrap := '1';

      when "010" =>                     -- read-only

        if CNTL.wacc='1'  or CNTL.macc='1' then

          abo_rdonly := '1';

        end if;

      when "100" =>                     -- read/write; trap on read&write

        dotrap := '1';

      when "101" =>                     -- read/write; trap on write

        dotrap := CNTL.wacc or CNTL.macc;

      when "110" => null;               -- read/write;

      when others =>                    -- unused codes: abort access

        abo_nonres := '1';

    end case;

    if IB_MREQ.we='1' and IBSEL_SSR0='1' then

      if IB_MREQ.be1 = '1' then

        nssr0.abo_nonres := IB_MREQ.din(ssr0_ibf_abo_nonres);

        nssr0.abo_length := IB_MREQ.din(ssr0_ibf_abo_length);

        nssr0.abo_rdonly := IB_MREQ.din(ssr0_ibf_abo_rdonly);

        nssr0.trap_mmu   := IB_MREQ.din(ssr0_ibf_trap_mmu);

        nssr0.ena_trap   := IB_MREQ.din(ssr0_ibf_ena_trap);

      end if;

      if IB_MREQ.be0 = '1' then

        nssr0.ena_mmu := IB_MREQ.din(ssr0_ibf_ena_mmu);

      end if;

    elsif nssr0.ena_mmu='1' and CNTL.cacc='0' then

      if dotrace = '1' then

        if MONI.istart = '1' then

          nssr0.inst_compl := '0';

        elsif MONI.idone = '1' then

          nssr0.inst_compl := '0';      -- disable instr.compl logic 

        end if;

      end if;

      if CNTL.req = '1' then

        AIB_WE <= '1';

        if ssr_freeze = '0' then

          nssr0.abo_nonres := abo_nonres;

          nssr0.abo_length := abo_length;

          nssr0.abo_rdonly := abo_rdonly;

        end if;

        doabort := abo_nonres or abo_length or abo_rdonly;

        if doabort = '0' then

          AIB_SETA <= '1';

          AIB_SETW <= CNTL.wacc or CNTL.macc;

        end if;

        if ssr_freeze = '0' then

          nssr0.dspace   := DSPACE;

          nssr0.seg_num  := asf;

          nssr0.seg_mode := CNTL.mode;

        end if;

      end if;

    end if;

    if CNTL.req='1' and R_SSR0.ena_mmu='1' and CNTL.cacc='0' and

       dotrap='1' then

      nssr0.trap_mmu := '1';

    end if;

    nssr0.trace_prev := dotrace;

    if MONI.trace_prev = '0' then

      TRACE <= dotrace;

    else

      TRACE <= R_SSR0.trace_prev;

    end if;

    N_SSR0 <= nssr0;

    if R_SSR0.ena_mmu='1' and CNTL.cacc='0' then

      STAT.vaok <= not doabort;

    else

      STAT.vaok <= '1';

    end if;

    if R_SSR0.ena_mmu='1' and CNTL.cacc='0' and doabort='0' and

       R_SSR0.ena_trap='1' and R_SSR0.trap_mmu='0' and dotrap='1' then

      STAT.trap <= '1';

    else

      STAT.trap <= '0';

    end if;

    STAT.ena_mmu   <= R_SSR0.ena_mmu;

    STAT.ena_22bit <= R_SSR3.ena_22bit;

    STAT.ena_ubmap <= R_SSR3.ena_ubmap;

  end process proc_nssr0;

end syn;