stella/src/emucore/Cart4KSC.cxx

//============================================================================
//
//   SSSS    tt          lll  lll       
//  SS  SS   tt           ll   ll        
//  SS     tttttt  eeee   ll   ll   aaaa 
//   SSSS    tt   ee  ee  ll   ll      aa
//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
//  SS  SS   tt   ee      ll   ll  aa  aa
//   SSSS     ttt  eeeee llll llll  aaaaa
//
// Copyright (c) 1995-2013 by Bradford W. Mott, Stephen Anthony
// and the Stella Team
//
// See the file "License.txt" for information on usage and redistribution of
// this file, and for a DISCLAIMER OF ALL WARRANTIES.
//
// $Id$
//============================================================================

#include <cassert>
#include <cstring>

#include "System.hxx"
#include "Cart4KSC.hxx"

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Cartridge4KSC::Cartridge4KSC(const uInt8* image, uInt32 size, const Settings& settings)
  : Cartridge(settings)
{
  // Copy the ROM image into my buffer
  memcpy(myImage, image, BSPF_min(4096u, size));
  createCodeAccessBase(4096);
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Cartridge4KSC::~Cartridge4KSC()
{
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Cartridge4KSC::reset()
{
  // Initialize RAM
  if(mySettings.getBool("ramrandom"))
    for(uInt32 i = 0; i < 128; ++i)
      myRAM[i] = mySystem->randGenerator().next();
  else
    memset(myRAM, 0, 128);
  myBankChanged = true;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void Cartridge4KSC::install(System& system)
{
  mySystem = &system;
  uInt16 shift = mySystem->pageShift();
  uInt16 mask = mySystem->pageMask();

  // Make sure the system we're being installed in has a page size that'll work
  assert(((0x1080 & mask) == 0) && ((0x1100 & mask) == 0));

  System::PageAccess access(0, 0, 0, this, System::PA_READ);

  // Set the page accessing method for the RAM writing pages
  access.type = System::PA_WRITE;
  for(uInt32 j = 0x1000; j < 0x1080; j += (1 << shift))
  {
    access.directPokeBase = &myRAM[j & 0x007F];
    access.codeAccessBase = &myCodeAccessBase[j & 0x007F];
    mySystem->setPageAccess(j >> shift, access);
  }

  // Set the page accessing method for the RAM reading pages
  access.directPokeBase = 0;
  access.type = System::PA_READ;
  for(uInt32 k = 0x1080; k < 0x1100; k += (1 << shift))
  {
    access.directPeekBase = &myRAM[k & 0x007F];
    access.codeAccessBase = &myCodeAccessBase[0x80 + (k & 0x007F)];
    mySystem->setPageAccess(k >> shift, access);
  }

  // Map ROM image into the system
  for(uInt32 address = 0x1100; address < 0x2000; address += (1 << shift))
  {
    access.directPeekBase = &myImage[address & 0x0FFF];
    access.codeAccessBase = &myCodeAccessBase[address & 0x0FFF];
    mySystem->setPageAccess(address >> mySystem->pageShift(), access);
  }
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt8 Cartridge4KSC::peek(uInt16 address)
{
  uInt16 peekAddress = address;
  address &= 0x0FFF;

  if(address < 0x0080)  // Write port is at 0xF000 - 0xF080 (128 bytes)
  {
    // Reading from the write port triggers an unwanted write
    uInt8 value = mySystem->getDataBusState(0xFF);

    if(bankLocked())
      return value;
    else
    {
      triggerReadFromWritePort(peekAddress);
      return myRAM[address] = value;
    }
  }  
  else
    return myImage[address & 0x0FFF];
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Cartridge4KSC::poke(uInt16 address, uInt8)
{
  // NOTE: This does not handle accessing RAM, however, this function
  // should never be called for RAM because of the way page accessing
  // has been setup
  return false;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Cartridge4KSC::bank(uInt16 bank)
{ 
  // Doesn't support bankswitching
  return false;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt16 Cartridge4KSC::bank() const
{
  return 0;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt16 Cartridge4KSC::bankCount() const
{
  return 1;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Cartridge4KSC::patch(uInt16 address, uInt8 value)
{
  address &= 0x0FFF;

  if(address < 0x0100)
  {
    // Normally, a write to the read port won't do anything
    // However, the patch command is special in that ignores such
    // cart restrictions
    myRAM[address & 0x007F] = value;
  }
  else
    myImage[address & 0xFFF] = value;

  return myBankChanged = true;
} 

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
const uInt8* Cartridge4KSC::getImage(int& size) const
{
  size = 4096;
  return myImage;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Cartridge4KSC::save(Serializer& out) const
{
  try
  {
    out.putString(name());
    out.putShort(myCurrentBank);
    out.putByteArray(myRAM, 128);
  }
  catch(...)
  {
    cerr << "ERROR: Cartridge4KSC::save" << endl;
    return false;
  }

  return true;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool Cartridge4KSC::load(Serializer& in)
{
  try
  {
    if(in.getString() != name())
      return false;

    myCurrentBank = in.getShort();
    in.getByteArray(myRAM, 128);
  }
  catch(...)
  {
    cerr << "ERROR: Cartridge4KSC::load" << endl;
    return false;
  }

  // Remember what bank we were in
  bank(myCurrentBank);

  return true;
}