MusicModuleMIDI.cc

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#include "MusicModuleMIDI.hh"
#include "serialize.hh"
 
namespace openmsx {
 
// MSX interface:
// port R/W
// 0    W    Control Register
// 1    W    Transmit Data Register
// 4    R    Status Register
// 5    R    Receive Data Register
 
// Some existing Music-Module detection routines:
// - fac demo 5: does OUT 0,3 : OUT 0,21 : INP(4) and expects to read 2
// - tetris 2 special edition: does INP(4) and expects to read 0
// - Synthesix: does INP(4), expects 0; OUT 0,3 : OUT 0,21: INP(4) and expects
//   bit 1 to be 1 and bit 2, 3 and 7 to be 0. Then does OUT 5,0xFE : INP(4)
//   and expects bit 1 to be 0.
// I did some _very_basic_ investigation and found the following:
// - after a reset reading from port 4 returns 0
// - after initializing the control register, reading port 4 returns 0 (of
//   course this will change when you start to actually receive/transmit data)
// - writing any value with the lower 2 bits set to 1 returns to the initial
//   state, and reading port 4 again returns 0.
// -  ?INP(4) : OUT0,3 : ?INP(4) : OUT0,21 : ? INP(4) : OUT0,3 :  ?INP(4)
//    outputs: 0, 0, 2, 0
 
MusicModuleMIDI::MusicModuleMIDI(const DeviceConfig& config)
        : MSXDevice(config)
        , mc6850(MSXDevice::getName(), getMotherBoard(), 500000) // 500 kHz
{
        reset(getCurrentTime());
}
 
void MusicModuleMIDI::reset(EmuTime::param time)
{
        mc6850.reset(time);
}
 
byte MusicModuleMIDI::readIO(word port, EmuTime::param /*time*/)
{
        switch (port & 0x1) {
        case 0:
                return mc6850.readStatusReg();
        case 1:
                return mc6850.readDataReg();
        }
        UNREACHABLE;
        return 0xFF;
}
 
byte MusicModuleMIDI::peekIO(word port, EmuTime::param /*time*/) const
{
        switch (port & 0x1) {
        case 0:
                return mc6850.peekStatusReg();
        case 1:
                return mc6850.peekDataReg();
        }
        UNREACHABLE;
        return 0xFF;
}
 
void MusicModuleMIDI::writeIO(word port, byte value, EmuTime::param time)
{
        switch (port & 0x01) {
        case 0:
                mc6850.writeControlReg(value, time);
                break;
        case 1:
                mc6850.writeDataReg(value, time);
                break;
        }
}
 
// versions 1-3: were for type "MC6850", see that class for details
// version 4: first version for "MusicModuleMIDI"
template<typename Archive>
void MusicModuleMIDI::serialize(Archive& ar, unsigned version)
{
        ar.template serializeBase<MSXDevice>(*this);
        if (ar.versionAtLeast(version, 4)) {
                ar.serialize("MC6850", mc6850);
        } else {
                // MC6850 members were serialized as direct children of the
                // <device> tag, without an intermediate <MC6850> tag.
                mc6850.serialize(ar, version);
        }
}
INSTANTIATE_SERIALIZE_METHODS(MusicModuleMIDI);
REGISTER_MSXDEVICE(MusicModuleMIDI, "MusicModuleMIDI");
 
// For backwards compatiblity, also register this class with the old name (only
// needed for loading from disk). Versions 1-3 use the old name "MC6850",
// version 4 (and above) use the name "MusicModuleMIDI".
static const RegisterInitializerHelper<XmlInputArchive, MusicModuleMIDI> registerbwCompat("MC6850");
 
} // namespace openmsx