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◆ main openmsx / src / memory / ESE_RAM.cc
3.3 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
/*
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 * MEGA-SCSI and ESE-RAM cartridge:
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 *  The mapping does SRAM and MB89352A(MEGA-SCSI) to ASCII8 or
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 *  an interchangeable bank controller.
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 *  The rest of this documentation is only about ESE-RAM specifically.
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 *
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 * Specification:
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 *  SRAM(MegaROM) controller: ASCII8 type
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 *  SRAM capacity           : 128, 256, 512 and 1024KB
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 *
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 * Bank changing address:
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 *  bank 4(0x4000-0x5fff): 0x6000 - 0x67FF (0x6000 used)
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 *  bank 6(0x6000-0x7fff): 0x6800 - 0x6FFF (0x6800 used)
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 *  bank 8(0x8000-0x9fff): 0x7000 - 0x77FF (0x7000 used)
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 *  bank A(0xa000-0xbfff): 0x7800 - 0x7FFF (0x7800 used)
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 *
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 * ESE-RAM Bank Map:
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 *  BANK 00H-7FH (read only)
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 *  BANK 80H-FFH (write and read. mirror of 00H-7FH)
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 */
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#include "ESE_RAM.hh"
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#include "MSXException.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 <cassert>
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namespace openmsx {
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size_t ESE_RAM::getSramSize() const
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{
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	size_t sramSize = getDeviceConfig().getChildDataAsInt("sramsize", 256); // size in kb
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	if (sramSize != one_of(1024u, 512u, 256u, 128u)) {
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		throw MSXException(
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			"SRAM size for ", getName(),
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			" should be 128, 256, 512 or 1024kB and not ",
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			sramSize, "kB!");
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	}
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	return sramSize * 1024; // in bytes
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}
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ESE_RAM::ESE_RAM(const DeviceConfig& config)
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	: MSXDevice(config)
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	, sram(getName() + " SRAM", getSramSize(), config)
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	, romBlockDebug(*this, mapped, 0x4000, 0x8000, 13)
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	, blockMask(narrow<byte>((sram.size() / 0x2000) - 1))
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{
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	reset(EmuTime::dummy());
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}
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void ESE_RAM::reset(EmuTime /*time*/)
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{
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	for (auto i : xrange(4)) {
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		setSRAM(i, 0);
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	}
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}
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byte ESE_RAM::readMem(uint16_t address, EmuTime /*time*/)
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{
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	if ((0x4000 <= address) && (address < 0xC000)) {
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		unsigned page = (address / 8192) - 2;
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		uint16_t addr = address & 0x1FFF;
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		return sram[8192 * mapped[page] + addr];
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	} else {
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		return 0xFF;
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	}
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}
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const byte* ESE_RAM::getReadCacheLine(uint16_t address) const
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{
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	if ((0x4000 <= address) && (address < 0xC000)) {
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		unsigned page = (address / 8192) - 2;
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		address &= 0x1FFF;
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		return &sram[8192 * mapped[page] + address];
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	} else {
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		return unmappedRead.data();
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	}
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}
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void ESE_RAM::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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		byte region = ((address >> 11) & 3);
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		setSRAM(region, value);
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	} else if ((0x4000 <= address) && (address < 0xC000)) {
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		unsigned page = (address / 8192) - 2;
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		address &= 0x1FFF;
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		if (isWriteable[page]) {
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			sram.write(8192 * mapped[page] + address, value);
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		}
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	}
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}
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byte* ESE_RAM::getWriteCacheLine(uint16_t address)
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{
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	if ((0x6000 <= address) && (address < 0x8000)) {
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		return nullptr;
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	} else if ((0x4000 <= address) && (address < 0xC000)) {
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		unsigned page = (address / 8192) - 2;
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		if (isWriteable[page]) {
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			return nullptr;
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		}
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	}
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	return unmappedWrite.data();
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}
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void ESE_RAM::setSRAM(unsigned region, byte block)
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{
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	invalidateDeviceRWCache(region * 0x2000 + 0x4000, 0x2000);
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	assert(region < 4);
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	isWriteable[region] = (block & 0x80) != 0;
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	mapped[region] = block & blockMask;
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}
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template<typename Archive>
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void ESE_RAM::serialize(Archive& ar, unsigned /*version*/)
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{
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	ar.template serializeBase<MSXDevice>(*this);
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	ar.serialize("SRAM",        sram,
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	             "isWriteable", isWriteable,
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	             "mapped",      mapped);
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}
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INSTANTIATE_SERIALIZE_METHODS(ESE_RAM);
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REGISTER_MSXDEVICE(ESE_RAM, "ESE_RAM");
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} // namespace openmsx