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◆ main openmsx / src / memory / MSXMapperIO.cc
4.2 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
#include "MSXMapperIO.hh"
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#include "HardwareConfig.hh"
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#include "MSXException.hh"
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#include "MSXMotherBoard.hh"
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#include "XMLElement.hh"
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#include "serialize.hh"
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#include "StringOp.hh"
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#include "enumerate.hh"
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#include "outer.hh"
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#include "stl.hh"
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namespace openmsx {
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[[nodiscard]] static byte calcReadBackMask(MSXMotherBoard& motherBoard)
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{
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	std::string_view type = motherBoard.getMachineConfig()->getConfig().getChildData(
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	                               "MapperReadBackBits", "largest");
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	if (type == "largest") {
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		return 0xff; // all bits can be read
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	}
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	auto bits = StringOp::stringTo<int>(type);
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	if (!bits) {
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		throw FatalError("Unknown mapper type: \"", type, "\".");
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	}
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	if (*bits < 0 || *bits > 8) {
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		throw FatalError("MapperReadBackBits out of range: \"", type, "\".");
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	}
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	return byte(~(unsigned(-1) << *bits));
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}
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MSXMapperIO::MSXMapperIO(const DeviceConfig& config)
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	: MSXDevice(config)
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	, debuggable(getMotherBoard(), getName())
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	, mask(calcReadBackMask(getMotherBoard()))
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{
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	reset(EmuTime::dummy());
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}
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void MSXMapperIO::setMode(Mode mode_, byte mask_, byte baseValue_)
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{
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	mode = mode_;
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	mask = mask_;
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	baseValue = baseValue_;
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}
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void MSXMapperIO::registerMapper(MSXMemoryMapperInterface* mapper)
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{
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	mappers.push_back(mapper);
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}
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void MSXMapperIO::unregisterMapper(MSXMemoryMapperInterface* mapper)
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{
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	mappers.erase(rfind_unguarded(mappers, mapper));
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}
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byte MSXMapperIO::readIO(uint16_t port, EmuTime time)
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{
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	byte value = [&] {
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		if (mode == Mode::EXTERNAL) {
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			byte result = 0xFF;
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			for (auto* mapper : mappers) {
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				result &= mapper->readIO(port, time);
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			}
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			return result;
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		} else {
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			return registers[port & 3];
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		}
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	}();
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	return (value & mask) | (baseValue & ~mask);
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}
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byte MSXMapperIO::peekIO(uint16_t port, EmuTime time) const
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{
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	byte value = [&] {
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		if (mode == Mode::EXTERNAL) {
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			byte result = 0xFF;
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			for (const auto* mapper : mappers) {
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				result &= mapper->peekIO(port, time);
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			}
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			return result;
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		} else {
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			return registers[port & 3];
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		}
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	}();
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	return (value & mask) | (baseValue & ~mask);
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}
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void MSXMapperIO::writeIO(uint16_t port, byte value, EmuTime time)
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{
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	registers[port & 3] = value;
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	// Note: the mappers are responsible for invalidating/filling the CPU
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	// cache-lines.
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	for (auto* mapper : mappers) {
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		mapper->writeIO(port, value, time);
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	}
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}
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// SimpleDebuggable
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// This debuggable is here for backwards compatibility. For more accurate
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// results, use the debuggable belonging to a specific mapper.
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MSXMapperIO::Debuggable::Debuggable(MSXMotherBoard& motherBoard_,
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                                    const std::string& name_)
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	: SimpleDebuggable(motherBoard_, name_, "Memory mapper registers", 4)
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{
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}
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byte MSXMapperIO::Debuggable::read(unsigned address)
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{
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	// return the last written value, with full 8-bit precision.
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	auto& mapperIO = OUTER(MSXMapperIO, debuggable);
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	return mapperIO.registers[address & 3];
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}
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void MSXMapperIO::Debuggable::readBlock(unsigned start, std::span<byte> output)
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{
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	auto& mapperIO = OUTER(MSXMapperIO, debuggable);
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	copy_to_range(std::span{mapperIO.registers}.subspan(start, output.size()), output);
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}
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void MSXMapperIO::Debuggable::write(unsigned address, byte value,
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                                    EmuTime time)
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{
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	auto& mapperIO = OUTER(MSXMapperIO, debuggable);
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	mapperIO.writeIO(narrow_cast<uint16_t>(address), value, time);
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}
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template<typename Archive>
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void MSXMapperIO::serialize(Archive& ar, unsigned version)
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{
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	if (ar.versionBelow(version, 2)) {
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		// In version 1 we stored the mapper state in MSXMapperIO instead of
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		// in the individual mappers, so distribute the state to them.
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		assert(Archive::IS_LOADER);
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		ar.serialize("registers", registers);
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		for (auto [page, reg] : enumerate(registers)) {
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			writeIO(uint16_t(page), reg, EmuTime::dummy());
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		}
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	}
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	if (ar.versionAtLeast(version, 3)) {
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		// In version 3 we store the mapper state BOTH here and in the
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		// individual mappers. The reason for this is:
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		// - There are MSX machines with a S1985 but without a memory
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		//   mapper. To support those we need to store the state here.
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		// - In rare cases (e.g. musical memory mapper) the mapper state
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		//   can be different for specific mappers.
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		ar.serialize("registers", registers);
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	}
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}
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INSTANTIATE_SERIALIZE_METHODS(MSXMapperIO);
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} // namespace openmsx