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◆ main openmsx / src / memory / RomAscii8kB.cc
1.7 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
e8555c89 Andy McCall 1 
// ASCII 8kB cartridges
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//
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// this type is used in many japanese-only cartridges.
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// example of cartridges: Valis(Fantasm Soldier), Dragon Slayer, Outrun,
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//                        Ashguine 2, ...
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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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// With 'reversedRegs' the same four registers exist, but they are wired to the
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// memory regions in the opposite order:
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//  0x4000 - 0x5fff: selected by 0x7800 - 0x7fff
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//  0x6000 - 0x7fff: selected by 0x7000 - 0x77ff
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//  0x8000 - 0x9fff: selected by 0x6800 - 0x6fff
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//  0xa000 - 0xbfff: selected by 0x6000 - 0x67ff
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// Used by the retail cartridge of XeGrader.
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#include "RomAscii8kB.hh"
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#include "serialize.hh"
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#include "xrange.hh"
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namespace openmsx {
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RomAscii8kB::RomAscii8kB(const DeviceConfig& config, Rom&& rom_,
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                         bool reversedRegs_)
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	: Rom8kBBlocks(config, std::move(rom_))
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	, reversedRegs(reversedRegs_)
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{
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	RomAscii8kB::reset(EmuTime::dummy());
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}
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void RomAscii8kB::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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}
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void RomAscii8kB::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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		auto reg = (address >> 11) & 3;
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		byte region = reversedRegs ? byte(5 - reg) : byte(reg + 2);
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		setRom(region, value);
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	}
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}
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byte* RomAscii8kB::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 {
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		return unmappedWrite.data();
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	}
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}
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REGISTER_MSXDEVICE(RomAscii8kB, "RomAscii8kB");
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} // namespace openmsx