ColecoSuperGameModule.cc

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#include "ColecoSuperGameModule.hh"
#include "DummyAY8910Periphery.hh"
#include "MSXCPUInterface.hh"
#include "MSXException.hh"
#include "serialize.hh"
 
namespace openmsx {
 
// Disabling the SGM RAM has no effect on 0-0x1FFF, according to Oscar Toledo.
// So, if the BIOS is disabled to show RAM and the SGM RAM is disabled, is
// there is 8kB SGM RAM on 0-0x1FFF.
 
static constexpr unsigned MAIN_RAM_AREA_START = 0x6000;
static constexpr unsigned MAIN_RAM_SIZE = 0x400; // 1kB
static constexpr unsigned SGM_RAM_SIZE = 0x8000; // 32kB
static constexpr unsigned BIOS_ROM_SIZE = 0x2000; // 8kB
 
ColecoSuperGameModule::ColecoSuperGameModule(const DeviceConfig& config)
        : MSXDevice(config)
        , psg(getName() + " PSG", DummyAY8910Periphery::instance(), config, getCurrentTime())
        , sgmRam(config, getName() + " RAM", "SGM RAM", SGM_RAM_SIZE)
        , mainRam(config, "Main RAM", "Main RAM", MAIN_RAM_SIZE)
        , biosRom(getName(), "BIOS ROM", config)
{
        if (biosRom.size() != BIOS_ROM_SIZE) {
                throw MSXException("ColecoVision BIOS ROM must be exactly 8kB in size.");
        }
        auto& cpuInterface = getCPUInterface();
        for (auto port : {0x50, 0x51, 0x53, 0x7F}) {
                cpuInterface.register_IO_Out(narrow_cast<byte>(port), this);
        }
        cpuInterface.register_IO_In(0x52, this);
        reset(getCurrentTime());
}
 
ColecoSuperGameModule::~ColecoSuperGameModule()
{
        auto& cpuInterface = getCPUInterface();
        for (auto port : {0x50, 0x51, 0x53, 0x7F}) {
                cpuInterface.unregister_IO_Out(narrow_cast<byte>(port), this);
        }
        cpuInterface.unregister_IO_In(0x52, this);
}
 
static constexpr unsigned translateMainRamAddress(unsigned address)
{
        return address & (MAIN_RAM_SIZE - 1);
}
 
void ColecoSuperGameModule::reset(EmuTime::param time)
{
        ramEnabled = false;
        ramAtBiosEnabled = false;
        psgLatch = 0;
        psg.reset(time);
        invalidateDeviceRWCache(); // flush all to be sure
}
 
byte ColecoSuperGameModule::readIO(word port, EmuTime::param time)
{
        if ((port & 0xFF) == 0x52) {
                return psg.readRegister(psgLatch, time);
        }
        return 0xFF;
}
 
byte ColecoSuperGameModule::peekIO(word port, EmuTime::param time) const
{
        if ((port & 0xFF) == 0x52) {
                return psg.peekRegister(psgLatch, time);
        }
        return 0xFF;
}
 
void ColecoSuperGameModule::writeIO(word port, byte value, EmuTime::param time)
{
        switch (port & 0xFF) {
                case 0x50: // PSG address (latch?)
                        psgLatch = value & 0x0F;
                        break;
                case 0x51: // PSG data (register write?)
                        psg.writeRegister(psgLatch, value, time);
                        break;
                case 0x53: // bit0=1 means enable SGM RAM in 0x2000-0x7FFF range
                        ramEnabled = (value & 1) != 0;
                        invalidateDeviceRWCache(0x0000, SGM_RAM_SIZE); // just flush the whole area
                        break;
                case 0x7F: // bit1=0 means enable SGM RAM in BIOS area (0-0x1FFF), 1 means BIOS
                        ramAtBiosEnabled = (value & 2) == 0;
                        invalidateDeviceRWCache(0x0000, BIOS_ROM_SIZE);
                        break;
                default:
                        // ignore
                        break;
        }
}
 
byte ColecoSuperGameModule::peekMem(word address, EmuTime::param /*time*/) const
{
        if (address < BIOS_ROM_SIZE) {
                return ramAtBiosEnabled ? sgmRam.peek(address) : biosRom[address];
        } else if (address < SGM_RAM_SIZE) {
                if (ramEnabled) {
                        return sgmRam.peek(address);
                } else if (address >= MAIN_RAM_AREA_START) {
                        return mainRam.peek(translateMainRamAddress(address));
                }
        }
        return 0xFF;
}
 
byte ColecoSuperGameModule::readMem(word address, EmuTime::param /*time*/)
{
        if (address < BIOS_ROM_SIZE) {
                return ramAtBiosEnabled ? sgmRam.read(address) : biosRom[address];
        } else if (address < SGM_RAM_SIZE) {
                if (ramEnabled) {
                        return sgmRam.read(address);
                } else if (address >= MAIN_RAM_AREA_START) {
                        return mainRam.read(translateMainRamAddress(address));
                }
        }
        return 0xFF;
}
 
void ColecoSuperGameModule::writeMem(word address, byte value, EmuTime::param /*time*/)
{
        if (address < BIOS_ROM_SIZE) {
                if (ramAtBiosEnabled) {
                        sgmRam.write(address, value);
                }
        } else if (address < SGM_RAM_SIZE) {
                if (ramEnabled) {
                        sgmRam.write(address, value);
                } else if (address >= MAIN_RAM_AREA_START) {
                        mainRam.write(translateMainRamAddress(address), value);
                }
        }
}
 
const byte* ColecoSuperGameModule::getReadCacheLine(word start) const
{
        if (start < BIOS_ROM_SIZE) {
                return ramAtBiosEnabled ? sgmRam.getReadCacheLine(start) : &biosRom[start];
        } else if (start < SGM_RAM_SIZE) {
                if (ramEnabled) {
                        return sgmRam.getReadCacheLine(start);
                } else if (start >= MAIN_RAM_AREA_START) {
                        return mainRam.getReadCacheLine(translateMainRamAddress(start));
                }
        }
        return unmappedRead.data();
}
 
byte* ColecoSuperGameModule::getWriteCacheLine(word start)
{
        if (start < BIOS_ROM_SIZE) {
                if (ramAtBiosEnabled) {
                        return sgmRam.getWriteCacheLine(start);
                }
        } else if (start < SGM_RAM_SIZE) {
                if (ramEnabled) {
                        return sgmRam.getWriteCacheLine(start);
                } else if (start >= MAIN_RAM_AREA_START) {
                        return mainRam.getWriteCacheLine(translateMainRamAddress(start));
                }
        }
        return unmappedWrite.data();
}
 
template<typename Archive>
void ColecoSuperGameModule::serialize(Archive& ar, unsigned /*version*/)
{
        ar.serialize("mainRam",          mainRam.getUncheckedRam(),
                     "sgmRam",           sgmRam.getUncheckedRam(),
                     "psg",              psg,
                     "psgLatch",         psgLatch,
                     "ramEnabled",       ramEnabled,
                     "ramAtBiosEnabled", ramAtBiosEnabled);
}
INSTANTIATE_SERIALIZE_METHODS(ColecoSuperGameModule);
REGISTER_MSXDEVICE(ColecoSuperGameModule, "ColecoSuperGameModule");
 
} // namespace openmsx