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◆ main openmsx / src / memory / RomColecoMegaCart.cc
1.7 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#include "RomColecoMegaCart.hh"
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#include "CacheLine.hh"
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#include "MSXException.hh"
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#include "serialize.hh"
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#include "one_of.hh"
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// information source:
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// https://github.com/openMSX/openMSX/files/2118720/MegaCart.FAQ.V1-2.pdf
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namespace openmsx {
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RomColecoMegaCart::RomColecoMegaCart(const DeviceConfig& config, Rom&& rom_)
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	: Rom16kBBlocks(config, std::move(rom_))
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{
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	if (auto size = rom.size() / 1024;
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	    size != one_of(128u, 256u, 512u, 1024u)) {
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		throw MSXException(
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			"MegaCart only supports ROMs of 128kB, 256kB, 512kB and 1024kB "
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			"size and not of ", size, "kB.");
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	}
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	reset(EmuTime::dummy());
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}
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void RomColecoMegaCart::reset(EmuTime /*time*/)
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{
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	setUnmapped(0);
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	setUnmapped(1);
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	// The first 16K of the cartridge (CV 8000h-BFFFh) is fixed and will
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	// always contain the highest/last 16K segment of the EPROM.
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	setRom(2, unsigned(-1)); // select last block
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	setRom(3, 0);
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	invalidateDeviceRCache(0xFFC0 & CacheLine::HIGH, CacheLine::SIZE);
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}
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byte RomColecoMegaCart::readMem(uint16_t address, EmuTime time)
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{
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	// The last 64 locations will switch banks (FFC0-FFFF). If you have
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	// fewer than 64 banks, then the strobe addresses simply repeat where
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	// they end. If you have 16 banks, then bank 0 can be strobed at FFC0,
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	// FFD0, FFE0, or FFF0.
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	if (address >= 0xFFC0) {
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		setRom(3, address); // mirroring is handled in superclass
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		invalidateDeviceRCache(0xFFC0 & CacheLine::HIGH, CacheLine::SIZE);
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	}
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	return Rom16kBBlocks::readMem(address, time);
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}
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const byte* RomColecoMegaCart::getReadCacheLine(uint16_t start) const
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{
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	if (start >= (0xFFC0 & CacheLine::HIGH)) {
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		return nullptr;
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	} else {
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		return Rom16kBBlocks::getReadCacheLine(start);
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	}
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}
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REGISTER_MSXDEVICE(RomColecoMegaCart, "RomColecoMegaCart");
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} // namespace openmsx