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◆ main openmsx / src / fdc / ToshibaFDC.cc
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#include "ToshibaFDC.hh"
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#include "DriveMultiplexer.hh"
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#include "WD2793.hh"
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#include "CacheLine.hh"
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#include "serialize.hh"
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// Based on studying the code in the Toshiba disk ROM.
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// Thanks to Arjen Zeilemaker for an annotated disassembly:
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//   https://sourceforge.net/p/msxsyssrc/git/ci/master/tree/diskdrvs/hx-f101/driver.mac
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//   https://sourceforge.net/p/msxsyssrc/git/ci/master/tree/diskdrvs/hx-34/driver.mac
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namespace openmsx {
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ToshibaFDC::ToshibaFDC(DeviceConfig& config)
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	: WD2793BasedFDC(config)
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{
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	// ROM only visible in 0x4000-0x7FFF by default
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	parseRomVisibility(config, 0x4000, 0x4000);
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}
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byte ToshibaFDC::readMem(uint16_t address, EmuTime time)
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{
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	switch (address) {
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	case 0x7FF0:
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		return controller.getStatusReg(time);
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	case 0x7FF1:
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		return controller.getTrackReg(time);
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	case 0x7FF2:
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		return controller.getSectorReg(time);
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	case 0x7FF3:
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		return controller.getDataReg(time);
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	case 0x7FF6:
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		return 0xFE | (multiplexer.diskChanged() ? 0 : 1);
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	case 0x7FF7: {
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		byte value = 0xFF;
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		if (controller.getIRQ(time))  value &= ~0x40;
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		if (controller.getDTRQ(time)) value &= ~0x80;
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		return value;
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	}
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	default:
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		return ToshibaFDC::peekMem(address, time);
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	}
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}
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byte ToshibaFDC::peekMem(uint16_t address, EmuTime time) const
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{
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	switch (address) { // checked on real HW: no mirroring
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	case 0x7FF0:
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		return controller.peekStatusReg(time);
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	case 0x7FF1:
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		return controller.peekTrackReg(time);
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	case 0x7FF2:
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		return controller.peekSectorReg(time);
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	case 0x7FF3:
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		return controller.peekDataReg(time);
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	case 0x7FF4:
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		// ToshibaFDC HX-F101 disk ROM doesn't read this, but HX-34
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		// does. No idea if this location is actually readable on
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		// HX-F101, but currently the emulation is the same for both.
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		return 0xFC
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		      | (multiplexer.getSide() ? 1 : 0)
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		      | (multiplexer.getMotor() ? 2 : 0);
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	case 0x7FF5:
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		return 0xFE | ((multiplexer.getSelectedDrive() == DriveMultiplexer::Drive::B) ? 1 : 0);
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	case 0x7FF6:
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		return 0xFE | (multiplexer.peekDiskChanged() ? 0 : 1);
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	case 0x7FF7: {
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		byte value = 0xFF; // unused bits read as 1
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		if (controller.peekIRQ(time))  value &= ~0x40;
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		if (controller.peekDTRQ(time)) value &= ~0x80;
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		return value;
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	}
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	default:
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		return MSXFDC::peekMem(address, time);
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	}
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}
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const byte* ToshibaFDC::getReadCacheLine(uint16_t start) const
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{
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	if ((start & CacheLine::HIGH) == (0x7FF0 & CacheLine::HIGH)) {
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		// FDC at 0x7FF0-0x7FF7
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		return nullptr;
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	} else {
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		return MSXFDC::getReadCacheLine(start);
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	}
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}
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void ToshibaFDC::writeMem(uint16_t address, byte value, EmuTime time)
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{
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	switch (address) {
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	case 0x7FF0:
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		controller.setCommandReg(value, time);
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		break;
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	case 0x7FF1:
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		controller.setTrackReg(value, time);
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		break;
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	case 0x7FF2:
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		controller.setSectorReg(value, time);
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		break;
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	case 0x7FF3:
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		controller.setDataReg(value, time);
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		break;
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	case 0x7FF4:
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		multiplexer.setSide((value & 0x01) != 0); // no effect on HX-F101 because it has single sided drive
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		multiplexer.setMotor((value & 0x02) != 0, time);
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		break;
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	case 0x7FF5:
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		// Disk ROM only writes the values 0 or 1.
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		multiplexer.selectDrive((value & 1) ? DriveMultiplexer::Drive::B
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		                                    : DriveMultiplexer::Drive::A,
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		                        time);
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		break;
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	case 0x7FF6:
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		// Disk ROM writes '1' (to drive A) and shortly after '0' (to drive B).
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		// TODO What does this do? Activate the 'disk is changed' state?
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		//      And if so, does the written value matter?
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		break;
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	case 0x7FF7:
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		// Probably no function, disk ROM doesn't write to this address.
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		break;
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	}
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}
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byte* ToshibaFDC::getWriteCacheLine(uint16_t address)
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{
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	if ((address & CacheLine::HIGH) == (0x7FF0 & CacheLine::HIGH)) {
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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 ToshibaFDC::serialize(Archive& ar, unsigned /*version*/)
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{
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	ar.template serializeBase<WD2793BasedFDC>(*this);
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}
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INSTANTIATE_SERIALIZE_METHODS(ToshibaFDC);
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REGISTER_MSXDEVICE(ToshibaFDC, "ToshibaFDC");
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} // namespace openmsx