Genesis-Plus-GX/source/memz80.c

/***************************************************************************************
 *  Genesis Plus
 *  Z80 bus address decoding (Genesis mode)
 *
 *  Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003  Charles Mac Donald (original code)
 *  Eke-Eke (2007,2008,2009), additional code & fixes for the GCN/Wii port
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, 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 more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 ****************************************************************************************/
#include "shared.h"

/*
  Handlers for access to unused addresses and those which make the
  machine lock up.
*/
static inline void z80_unused_w(unsigned int address, unsigned int data)
{
#ifdef LOGERROR
  error("Z80 unused write %04X = %02X\n", address, data);
#endif
}

static inline unsigned int z80_unused_r(unsigned int address)
{
#ifdef LOGERROR
  error("Z80 unused read %04X\n", address);
#endif
  return 0xff;
}

static inline void z80_lockup_w(unsigned int address, unsigned int data)
{
#ifdef LOGERROR
  error("Z80 lockup write %04X = %02X\n", address, data);
#endif
  if (!config.force_dtack)
  {
    mcycles_z80 = 0xffffffff;
    zstate = 0;
  }
}

static inline unsigned int z80_lockup_r(unsigned int address)
{
#ifdef LOGERROR
  error("Z80 lockup read %04X\n", address);
#endif
  if (!config.force_dtack)
  {
    mcycles_z80 = 0xffffffff;
    zstate = 0;
  }
  return 0xff;
}


/*
    Z80 memory handlers
*/
unsigned int cpu_readmem16(unsigned int address)
{
  switch((address >> 13) & 7)
  {
    case 0: /* Work RAM */
    case 1:
    {
      return zram[address & 0x1fff];
    }

    case 2: /* YM2612 */
    {
      return fm_read(mcycles_68k, address & 3);
    }

    case 3: /* VDP */
    {
      if ((address >> 8) == 0x7f)
      {
        return (*zbank_memory_map[0xc0].read)(address);
      }
      return z80_unused_r(address);
    }
      
    default: /* V-bus bank */
    {
      address = zbank | (address & 0x7fff);
      unsigned int slot = address >> 16;
      if (zbank_memory_map[slot].read)
      {
        return (*zbank_memory_map[slot].read)(address);
      }
      return READ_BYTE(m68k_memory_map[slot].base, address & 0xffff);
    }
  }
}


void cpu_writemem16(unsigned int address, unsigned int data)
{
  switch((address >> 13) & 7)
  {
    case 0: /* Work RAM */
    case 1: 
    {
      zram[address & 0x1fff] = data;
      return;
    }

    case 2: /* YM2612 */
    {
      fm_write(mcycles_z80, address & 3, data);
      return;
    }

    case 3: /* Bank register and VDP */
    {
      switch(address >> 8)
      {
        case 0x60:
        {
          gen_zbank_w(data & 1);
          return;
        }

        case 0x7f:
        {
          (*zbank_memory_map[0xc0].write)(address, data);
          return;
        }

        default:
        {
          z80_unused_w(address, data);
          return;
        }
      }
    }

    default: /* V-bus bank */
    {
      address = zbank | (address & 0x7fff);
      unsigned int slot = address >> 16;
      if (zbank_memory_map[slot].write)
      {
        (*zbank_memory_map[slot].write)(address, data);
        return;
      }
      WRITE_BYTE(m68k_memory_map[slot].base, address & 0xffff, data);
      return;
    }
  }
}

/*
  Port handlers. Ports are unused when not in Mark III compatability mode.

  Games that access ports anyway:
    Thunder Force IV reads port $BF in it's interrupt handler.
*/

unsigned int cpu_readport16(unsigned int port)
{
#if LOGERROR
  error("Z80 read port %04X\n", port);
#endif
  return 0xff;
}

void cpu_writeport16(unsigned int port, unsigned int data)
{
#if LOGERROR
  error("Z80 write %02X to port %04X\n", data, port);
#endif
}