MSXFmPac.cc

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#include "MSXFmPac.hh"
#include "CacheLine.hh"
#include "serialize.hh"
 
namespace openmsx {
 
static constexpr const char* const PAC_Header = "PAC2 BACKUP DATA";
 
MSXFmPac::MSXFmPac(const DeviceConfig& config)
        : MSXMusicBase(config)
        , sram(getName() + " SRAM", 0x1FFE, config, PAC_Header)
        , romBlockDebug(*this, std::span{&bank, 1}, 0x4000, 0x4000, 14)
{
        reset(getCurrentTime());
}
 
void MSXFmPac::reset(EmuTime::param time)
{
        MSXMusicBase::reset(time);
        enable = 0;
        sramEnabled = false;
        bank = 0;
        r1ffe = r1fff = 0; // actual value doesn't matter as long
                           // as it's not the magic combination
}
 
void MSXFmPac::writeIO(word port, byte value, EmuTime::param time)
{
        if (enable & 1) {
                MSXMusicBase::writeIO(port, value, time);
        }
}
 
byte MSXFmPac::readMem(word address, EmuTime::param /*time*/)
{
        address &= 0x3FFF;
        switch (address) {
        case 0x3FF6:
                return enable;
        case 0x3FF7:
                return bank;
        default:
                if (sramEnabled) {
                        if (address < 0x1FFE) {
                                return sram[address];
                        } else if (address == 0x1FFE) {
                                return r1ffe; // always 0x4D
                        } else if (address == 0x1FFF) {
                                return r1fff; // always 0x69
                        } else {
                                return 0xFF;
                        }
                } else {
                        return rom[bank * 0x4000 + address];
                }
        }
}
 
const byte* MSXFmPac::getReadCacheLine(word address) const
{
        address &= 0x3FFF;
        if (address == (0x3FF6 & CacheLine::HIGH)) {
                return nullptr;
        }
        if (sramEnabled) {
                if (address < (0x1FFE & CacheLine::HIGH)) {
                        return &sram[address];
                } else if (address == (0x1FFE & CacheLine::HIGH)) {
                        return nullptr;
                } else {
                        return unmappedRead.data();
                }
        } else {
                return &rom[bank * 0x4000 + address];
        }
}
 
void MSXFmPac::writeMem(word address, byte value, EmuTime::param time)
{
        // 'enable' has no effect for memory mapped access
        //   (thanks to BiFiMSX for investigating this)
        address &= 0x3FFF;
        switch (address) {
        case 0x1FFE:
                if (!(enable & 0x10)) {
                        r1ffe = value;
                        checkSramEnable();
                }
                break;
        case 0x1FFF:
                if (!(enable & 0x10)) {
                        r1fff = value;
                        checkSramEnable();
                }
                break;
        case 0x3FF4: // address
        case 0x3FF5: // data
                writePort(address & 1, value, time);
                break;
        case 0x3FF6:
                enable = value & 0x11;
                if (enable & 0x10) {
                        r1ffe = r1fff = 0; // actual value not important
                        checkSramEnable();
                }
                break;
        case 0x3FF7: {
                if (byte newBank = value & 0x03; bank != newBank) {
                        bank = newBank;
                        invalidateDeviceRCache();
                }
                break;
        }
        default:
                if (sramEnabled && (address < 0x1FFE)) {
                        sram.write(address, value);
                }
        }
}
 
byte* MSXFmPac::getWriteCacheLine(word address)
{
        address &= 0x3FFF;
        if (address == (0x1FFE & CacheLine::HIGH)) {
                return nullptr;
        }
        if (address == (0x3FF4 & CacheLine::HIGH)) {
                return nullptr;
        }
        if (sramEnabled && (address < 0x1FFE)) {
                return nullptr;
        } else {
                return unmappedWrite.data();
        }
}
 
void MSXFmPac::checkSramEnable()
{
        bool newEnabled = (r1ffe == 0x4D) && (r1fff == 0x69);
        if (sramEnabled != newEnabled) {
                sramEnabled = newEnabled;
                invalidateDeviceRWCache();
        }
}
 
 
template<typename Archive>
void MSXFmPac::serialize(Archive& ar, unsigned version)
{
        ar.template serializeInlinedBase<MSXMusicBase>(*this, version);
        ar.serialize("sram",   sram,
                     "enable", enable,
                     "bank",   bank,
                     "r1ffe",  r1ffe,
                     "r1fff",  r1fff);
        if constexpr (Archive::IS_LOADER) {
                // sramEnabled can be calculated
                checkSramEnable();
        }
}
INSTANTIATE_SERIALIZE_METHODS(MSXFmPac);
REGISTER_MSXDEVICE(MSXFmPac, "FM-PAC");
 
} // namespace openmsx