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◆ main openmsx / src / serial / MusicModuleMIDI.cc
2.8 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#include "MusicModuleMIDI.hh"
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#include "serialize.hh"
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namespace openmsx {
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// MSX interface:
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// port R/W
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// 0    W    Control Register
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// 1    W    Transmit Data Register
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// 4    R    Status Register
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// 5    R    Receive Data Register
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// Some existing Music-Module detection routines:
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// - fac demo 5: does OUT 0,3 : OUT 0,21 : INP(4) and expects to read 2
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// - tetris 2 special edition: does INP(4) and expects to read 0
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// - Synthesix: does INP(4), expects 0; OUT 0,3 : OUT 0,21: INP(4) and expects
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//   bit 1 to be 1 and bit 2, 3 and 7 to be 0. Then does OUT 5,0xFE : INP(4)
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//   and expects bit 1 to be 0.
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// I did some _very_basic_ investigation and found the following:
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// - after a reset reading from port 4 returns 0
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// - after initializing the control register, reading port 4 returns 0 (of
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//   course this will change when you start to actually receive/transmit data)
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// - writing any value with the lower 2 bits set to 1 returns to the initial
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//   state, and reading port 4 again returns 0.
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// -  ?INP(4) : OUT0,3 : ?INP(4) : OUT0,21 : ? INP(4) : OUT0,3 :  ?INP(4)
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//    outputs: 0, 0, 2, 0
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MusicModuleMIDI::MusicModuleMIDI(const DeviceConfig& config)
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	: MSXDevice(config)
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	, mc6850(MSXDevice::getName(), getMotherBoard(), 500000) // 500 kHz
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{
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	reset(getCurrentTime());
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}
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void MusicModuleMIDI::reset(EmuTime time)
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{
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	mc6850.reset(time);
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}
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uint8_t MusicModuleMIDI::readIO(uint16_t port, EmuTime /*time*/)
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{
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	switch (port & 0x1) {
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	case 0:
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		return mc6850.readStatusReg();
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	case 1:
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		return mc6850.readDataReg();
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	}
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	UNREACHABLE;
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}
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uint8_t MusicModuleMIDI::peekIO(uint16_t port, EmuTime /*time*/) const
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{
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	switch (port & 0x1) {
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	case 0:
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		return mc6850.peekStatusReg();
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	case 1:
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		return mc6850.peekDataReg();
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	}
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	UNREACHABLE;
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}
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void MusicModuleMIDI::writeIO(uint16_t port, uint8_t value, EmuTime time)
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{
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	switch (port & 0x01) {
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	case 0:
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		mc6850.writeControlReg(value, time);
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		break;
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	case 1:
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		mc6850.writeDataReg(value, time);
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		break;
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	}
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}
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// versions 1-3: were for type "MC6850", see that class for details
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// version 4: first version for "MusicModuleMIDI"
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template<typename Archive>
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void MusicModuleMIDI::serialize(Archive& ar, unsigned version)
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{
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	ar.template serializeBase<MSXDevice>(*this);
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	if (ar.versionAtLeast(version, 4)) {
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		ar.serialize("MC6850", mc6850);
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	} else {
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		// MC6850 members were serialized as direct children of the
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		// <device> tag, without an intermediate <MC6850> tag.
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		mc6850.serialize(ar, version);
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	}
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}
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INSTANTIATE_SERIALIZE_METHODS(MusicModuleMIDI);
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REGISTER_MSXDEVICE(MusicModuleMIDI, "MusicModuleMIDI");
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// For backwards compatiblity, also register this class with the old name (only
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// needed for loading from disk). Versions 1-3 use the old name "MC6850",
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// version 4 (and above) use the name "MusicModuleMIDI".
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static const RegisterInitializerHelper<XmlInputArchive, MusicModuleMIDI> registerbwCompat("MC6850");
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} // namespace openmsx