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◆ main openmsx / src / memory / RomAscii8_8.cc
3.9 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
// ASCII 8kB based cartridges with SRAM
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//   - ASCII8-8  /  KOEI-8  /  KOEI-32  /  WIZARDRY / ASCII8-2
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//
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// The address to change banks:
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//  bank 1: 0x6000 - 0x67ff (0x6000 used)
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//  bank 2: 0x6800 - 0x6fff (0x6800 used)
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//  bank 3: 0x7000 - 0x77ff (0x7000 used)
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//  bank 4: 0x7800 - 0x7fff (0x7800 used)
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//
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//  To select SRAM set bit 7 (for WIZARDRY) or the bit just above the
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//  rom selection bits (bit 5/6/7 depending on ROM size). For KOEI-32
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//  the lowest bits indicate which SRAM page is selected. SRAM is
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//  readable at 0x8000-0xBFFF. For the KOEI-x types SRAM is also
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//  readable at 0x4000-0x5FFF
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#include "RomAscii8_8.hh"
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#include "SRAM.hh"
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#include "narrow.hh"
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#include "one_of.hh"
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#include "serialize.hh"
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#include "xrange.hh"
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#include <memory>
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namespace openmsx {
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RomAscii8_8::RomAscii8_8(const DeviceConfig& config,
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                         Rom&& rom_, SubType subType)
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	: Rom8kBBlocks(config, std::move(rom_))
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	, sramEnableBit((subType == SubType::WIZARDRY) ? 0x80
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	                                      : narrow_cast<byte>(rom.size() / BANK_SIZE))
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	, sramPages((subType == one_of(SubType::KOEI_8, SubType::KOEI_32)) ? 0x34 : 0x30)
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{
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	unsigned size = (subType == one_of(SubType::KOEI_32, SubType::ASCII8_32)) ? 0x8000  // 32kB
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	              : (subType == SubType::ASCII8_2) ? 0x0800  //  2kB
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	                                      : 0x2000; //  8kB
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	sram = std::make_unique<SRAM>(getName() + " SRAM", size, config);
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	reset(EmuTime::dummy());
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}
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void RomAscii8_8::reset(EmuTime /*time*/)
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{
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	setUnmapped(0);
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	setUnmapped(1);
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	for (auto i : xrange(2, 6)) {
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		setRom(i, 0);
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	}
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	setUnmapped(6);
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	setUnmapped(7);
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	sramEnabled = 0;
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}
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byte RomAscii8_8::readMem(uint16_t address, EmuTime time)
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{
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	auto bank = narrow<byte>(address / BANK_SIZE);
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	if ((1 << bank) & sramEnabled) {
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		// read from SRAM (possibly mirror)
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		auto addr = (sramBlock[bank] * BANK_SIZE)
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		          + (address & (sram->size() - 1) & BANK_MASK);
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		return (*sram)[addr];
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	} else {
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		return Rom8kBBlocks::readMem(address, time);
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	}
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}
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const byte* RomAscii8_8::getReadCacheLine(uint16_t address) const
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{
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	auto bank = narrow<byte>(address / BANK_SIZE);
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	if ((1 << bank) & sramEnabled) {
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		// read from SRAM (possibly mirror)
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		auto addr = (sramBlock[bank] * BANK_SIZE)
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		          + (address & (sram->size() - 1) & BANK_MASK);
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		return &(*sram)[addr];
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	} else {
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		return Rom8kBBlocks::getReadCacheLine(address);
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	}
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}
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void RomAscii8_8::writeMem(uint16_t address, byte value, EmuTime /*time*/)
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{
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	if ((0x6000 <= address) && (address < 0x8000)) {
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		// bank switching
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		byte region = ((address >> 11) & 3) + 2;
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		if (value & sramEnableBit) {
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			auto mask = narrow_cast<byte>((sram->size() + BANK_MASK) / BANK_SIZE - 1); // round up;
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			sramEnabled |= (1 << region) & sramPages;
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			sramBlock[region] = value & mask;
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			setBank(region, &(*sram)[sramBlock[region] * BANK_SIZE], value);
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			invalidateDeviceRCache(0x2000 * region, 0x2000); // do not cache
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		} else {
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			sramEnabled &= byte(~(1 << region));
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			setRom(region, value);
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		}
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		// 'R' is already handled
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		invalidateDeviceWCache(0x2000 * region, 0x2000);
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	} else {
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		auto bank = narrow<byte>(address / BANK_SIZE);
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		if ((1 << bank) & sramEnabled) {
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			// write to SRAM (possibly mirror)
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			auto addr = (sramBlock[bank] * BANK_SIZE)
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			          + (address & (sram->size() - 1) & BANK_MASK);
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			sram->write(addr, value);
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		}
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	}
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}
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byte* RomAscii8_8::getWriteCacheLine(uint16_t address)
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{
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	if ((0x6000 <= address) && (address < 0x8000)) {
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		// bank switching
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		return nullptr;
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	} else if ((1 << (address / BANK_SIZE)) & sramEnabled) {
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		// write to SRAM
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		return nullptr;
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	} else {
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		return unmappedWrite.data();
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	}
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}
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template<typename Archive>
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void RomAscii8_8::serialize(Archive& ar, unsigned /*version*/)
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{
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	ar.template serializeBase<Rom8kBBlocks>(*this);
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	ar.serialize("sramEnabled", sramEnabled,
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	             "sramBlock",   sramBlock);
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}
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INSTANTIATE_SERIALIZE_METHODS(RomAscii8_8);
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REGISTER_MSXDEVICE(RomAscii8_8, "RomAscii8_8");
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} // namespace openmsx