stella/src/emucore/CartFE.cxx

174 lines
4.7 KiB
C++

//============================================================================
//
// 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) 1995-2017 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.
//============================================================================
#include "M6532.hxx"
#include "System.hxx"
#include "CartFE.hxx"
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
CartridgeFE::CartridgeFE(const BytePtr& image, uInt32 size,
const Settings& settings)
: Cartridge(settings),
myBankOffset(0),
myLastAccessWasFE(false)
{
// Copy the ROM image into my buffer
memcpy(myImage, image.get(), std::min(8192u, size));
createCodeAccessBase(8192);
myStartBank = 0; // For now, we assume this; more research is needed
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void CartridgeFE::reset()
{
bank(myStartBank);
myLastAccessWasFE = false;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void CartridgeFE::install(System& system)
{
mySystem = &system;
// The hotspot $01FE is in a mirror of zero-page RAM
// We need to claim access to it here, and deal with it in peek/poke below
System::PageAccess access(this, System::PA_READWRITE);
for(uInt16 addr = 0x180; addr < 0x200; addr += System::PAGE_SIZE)
mySystem->setPageAccess(addr, access);
// Map all of the cart accesses to call peek and poke
access.type = System::PA_READ;
for(uInt16 addr = 0x1000; addr < 0x2000; addr += System::PAGE_SIZE)
mySystem->setPageAccess(addr, access);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt8 CartridgeFE::peek(uInt16 address)
{
uInt8 value = (address < 0x200) ? mySystem->m6532().peek(address) :
myImage[myBankOffset + (address & 0x0FFF)];
// Check if we hit hotspot
checkBankSwitch(address, value);
return value;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeFE::poke(uInt16 address, uInt8 value)
{
if(address < 0x200)
mySystem->m6532().poke(address, value);
// Check if we hit hotspot
checkBankSwitch(address, value);
return false;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
void CartridgeFE::checkBankSwitch(uInt16 address, uInt8 value)
{
if(bankLocked())
return;
// Did we detect $01FE on the last address bus access?
// If so, we bankswitch according to the upper 3 bits of the data bus
// NOTE: see the header file for the significance of 'value & 0x20'
if(myLastAccessWasFE)
bank((value & 0x20) ? 0 : 1);
// On the next cycle, we use the (then) current data bus value to decode
// the bank to use
myLastAccessWasFE = address == 0x01FE;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeFE::bank(uInt16 bank)
{
if(bankLocked())
return false;
myBankOffset = bank << 12;
return myBankChanged = true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt16 CartridgeFE::getBank() const
{
return myBankOffset >> 12;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
uInt16 CartridgeFE::bankCount() const
{
return 2;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeFE::patch(uInt16 address, uInt8 value)
{
myImage[myBankOffset + (address & 0x0FFF)] = value;
return myBankChanged = true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
const uInt8* CartridgeFE::getImage(uInt32& size) const
{
size = 8192;
return myImage;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeFE::save(Serializer& out) const
{
try
{
out.putString(name());
out.putShort(myBankOffset);
out.putBool(myLastAccessWasFE);
}
catch(...)
{
cerr << "ERROR: CartridgeFE::save" << endl;
return false;
}
return true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
bool CartridgeFE::load(Serializer& in)
{
try
{
if(in.getString() != name())
return false;
myBankOffset = in.getShort();
myLastAccessWasFE = in.getBool();
}
catch(...)
{
cerr << "ERROR: CartridgeF8SC::load" << endl;
return false;
}
return true;
}