ToshibaFDC.cc

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#include "ToshibaFDC.hh"
#include "CacheLine.hh"
#include "DriveMultiplexer.hh"
#include "WD2793.hh"
#include "serialize.hh"
 
// Based on studying the code in the Toshiba disk ROM.
// Thanks to Arjen Zeilemaker for an annotated disassembly:
//   https://sourceforge.net/p/msxsyssrc/git/ci/master/tree/diskdrvs/hx-f101/driver.mac
//   https://sourceforge.net/p/msxsyssrc/git/ci/master/tree/diskdrvs/hx-34/driver.mac
 
namespace openmsx {
 
ToshibaFDC::ToshibaFDC(const DeviceConfig& config)
        : WD2793BasedFDC(config)
{
}
 
byte ToshibaFDC::readMem(word address, EmuTime::param time)
{
        switch (address) {
        case 0x7FF0:
                return controller.getStatusReg(time);
        case 0x7FF1:
                return controller.getTrackReg(time);
        case 0x7FF2:
                return controller.getSectorReg(time);
        case 0x7FF3:
                return controller.getDataReg(time);
        case 0x7FF6:
                return 0xFE | (multiplexer.diskChanged() ? 0 : 1);
        case 0x7FF7: {
                byte value = 0xFF;
                if (controller.getIRQ(time))  value &= ~0x40;
                if (controller.getDTRQ(time)) value &= ~0x80;
                return value;
        }
        default:
                return ToshibaFDC::peekMem(address, time);
        }
}
 
byte ToshibaFDC::peekMem(word address, EmuTime::param time) const
{
        switch (address) { // checked on real HW: no mirroring
        case 0x7FF0:
                return controller.peekStatusReg(time);
        case 0x7FF1:
                return controller.peekTrackReg(time);
        case 0x7FF2:
                return controller.peekSectorReg(time);
        case 0x7FF3:
                return controller.peekDataReg(time);
        case 0x7FF4:
                // ToshibaFDC HX-F101 disk ROM doesn't read this, but HX-34
                // does. No idea if this location is actually readable on
                // HX-F101, but currently the emulation is the same for both.
                return 0xFC
                      | (multiplexer.getSide() ? 1 : 0)
                      | (multiplexer.getMotor() ? 2 : 0);
        case 0x7FF5:
                return 0xFE | ((multiplexer.getSelectedDrive() == DriveMultiplexer::Drive::B) ? 1 : 0);
        case 0x7FF6:
                return 0xFE | (multiplexer.peekDiskChanged() ? 0 : 1);
        case 0x7FF7: {
                byte value = 0xFF; // unused bits read as 1
                if (controller.peekIRQ(time))  value &= ~0x40;
                if (controller.peekDTRQ(time)) value &= ~0x80;
                return value;
        }
        default:
                if (0x4000 <= address && address < 0x8000) {
                        // ROM only visible in 0x4000-0x7FFF.
                        return MSXFDC::peekMem(address, time);
                } else {
                        return 0xFF;
                }
        }
}
 
const byte* ToshibaFDC::getReadCacheLine(word start) const
{
        if ((start & CacheLine::HIGH) == (0x7FF0 & CacheLine::HIGH)) {
                // FDC at 0x7FF0-0x7FF7
                return nullptr;
        } else if (0x4000 <= start && start < 0x8000) {
                // ROM at 0x4000-0x7FFF
                return MSXFDC::getReadCacheLine(start);
        } else {
                return unmappedRead.data();
        }
}
 
void ToshibaFDC::writeMem(word address, byte value, EmuTime::param time)
{
        switch (address) {
        case 0x7FF0:
                controller.setCommandReg(value, time);
                break;
        case 0x7FF1:
                controller.setTrackReg(value, time);
                break;
        case 0x7FF2:
                controller.setSectorReg(value, time);
                break;
        case 0x7FF3:
                controller.setDataReg(value, time);
                break;
        case 0x7FF4:
                multiplexer.setSide((value & 0x01) != 0); // no effect on HX-F101 because it has single sided drive
                multiplexer.setMotor((value & 0x02) != 0, time);
                break;
        case 0x7FF5:
                // Disk ROM only writes the values 0 or 1.
                multiplexer.selectDrive((value & 1) ? DriveMultiplexer::Drive::B
                                                    : DriveMultiplexer::Drive::A,
                                        time);
                break;
        case 0x7FF6:
                // Disk ROM writes '1' (to drive A) and shortly after '0' (to drive B).
                // TODO What does this do? Activate the 'disk is changed' state?
                //      And if so, does the written value matter?
                break;
        case 0x7FF7:
                // Probably no function, disk ROM doesn't write to this address.
                break;
        }
}
 
byte* ToshibaFDC::getWriteCacheLine(word address)
{
        if ((address & CacheLine::HIGH) == (0x7FF0 & CacheLine::HIGH)) {
                return nullptr;
        } else {
                return unmappedWrite.data();
        }
}
 
template<typename Archive>
void ToshibaFDC::serialize(Archive& ar, unsigned /*version*/)
{
        ar.template serializeBase<WD2793BasedFDC>(*this);
}
INSTANTIATE_SERIALIZE_METHODS(ToshibaFDC);
REGISTER_MSXDEVICE(ToshibaFDC, "ToshibaFDC");
 
} // namespace openmsx