NationalFDC.cc

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#include "NationalFDC.hh"
#include "CacheLine.hh"
#include "DriveMultiplexer.hh"
#include "WD2793.hh"
#include "serialize.hh"
 
namespace openmsx {
 
NationalFDC::NationalFDC(const DeviceConfig& config)
        : WD2793BasedFDC(config)
{
}
 
byte NationalFDC::readMem(word address, EmuTime::param time)
{
        switch (address & 0x3FC7) {
        case 0x3F80:
                return controller.getStatusReg(time);
        case 0x3F81:
                return controller.getTrackReg(time);
        case 0x3F82:
                return controller.getSectorReg(time);
        case 0x3F83:
                return controller.getDataReg(time);
        case 0x3F84:
        case 0x3F85:
        case 0x3F86:
        case 0x3F87: {
                byte value = 0x7F;
                if (controller.getIRQ(time))  value |=  0x80;
                if (controller.getDTRQ(time)) value &= ~0x40;
                return value;
        }
        default:
                return NationalFDC::peekMem(address, time);
        }
}
 
byte NationalFDC::peekMem(word address, EmuTime::param time) const
{
        // According to atarulum:
        //  7FBC        is mirrored in 7FBC - 7FBF
        //  7FB8 - 7FBF is mirrored in 7F80 - 7FBF
        switch (address & 0x3FC7) {
        case 0x3F80:
                return controller.peekStatusReg(time);
        case 0x3F81:
                return controller.peekTrackReg(time);
        case 0x3F82:
                return controller.peekSectorReg(time);
        case 0x3F83:
                return controller.peekDataReg(time);
        case 0x3F84:
        case 0x3F85:
        case 0x3F86:
        case 0x3F87: {
                // Drive control IRQ and DRQ lines are not connected to Z80 interrupt request
                // bit 7: intrq
                // bit 6: !dtrq
                // other bits read 1
                byte value = 0x7F;
                if (controller.peekIRQ(time))  value |=  0x80;
                if (controller.peekDTRQ(time)) value &= ~0x40;
                return value;
        }
        default:
                if (address < 0x8000) {
                        // ROM only visible in 0x0000-0x7FFF
                        return MSXFDC::peekMem(address, time);
                } else {
                        return 255;
                }
        }
}
 
const byte* NationalFDC::getReadCacheLine(word start) const
{
        if ((start & 0x3FC0 & CacheLine::HIGH) == (0x3F80 & CacheLine::HIGH)) {
                // FDC at 0x7FB8-0x7FBC (also mirrored)
                return nullptr;
        } else if (start < 0x8000) {
                // ROM at 0x0000-0x7FFF
                return MSXFDC::getReadCacheLine(start);
        } else {
                return unmappedRead.data();
        }
}
 
void NationalFDC::writeMem(word address, byte value, EmuTime::param time)
{
        switch (address & 0x3FC7) {
        case 0x3F80:
                controller.setCommandReg(value, time);
                break;
        case 0x3F81:
                controller.setTrackReg(value, time);
                break;
        case 0x3F82:
                controller.setSectorReg(value, time);
                break;
        case 0x3F83:
                controller.setDataReg(value, time);
                break;
        case 0x3F84:
        case 0x3F85:
        case 0x3F86:
        case 0x3F87:
                // bit 0 -> select drive 0
                // bit 1 -> select drive 1
                // bit 2 -> side select
                // bit 3 -> motor on
                auto drive = [&] {
                        switch (value & 3) {
                                case 1:  return DriveMultiplexer::DRIVE_A;
                                case 2:  return DriveMultiplexer::DRIVE_B;
                                default: return DriveMultiplexer::NO_DRIVE;
                        }
                }();
                multiplexer.selectDrive(drive, time);
                multiplexer.setSide((value & 0x04) != 0);
                multiplexer.setMotor((value & 0x08) != 0, time);
                break;
        }
}
 
byte* NationalFDC::getWriteCacheLine(word address) const
{
        if ((address & 0x3FC0) == (0x3F80 & CacheLine::HIGH)) {
                // FDC at 0x7FB8-0x7FBC (also mirrored)
                return nullptr;
        } else {
                return unmappedWrite.data();
        }
}
 
 
template<typename Archive>
void NationalFDC::serialize(Archive& ar, unsigned /*version*/)
{
        ar.template serializeBase<WD2793BasedFDC>(*this);
}
INSTANTIATE_SERIALIZE_METHODS(NationalFDC);
REGISTER_MSXDEVICE(NationalFDC, "NationalFDC");
 
} // namespace openmsx