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◆ main openmsx / src / MSXHiResTimer.cc
1.3 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#include "MSXHiResTimer.hh"
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#include "serialize.hh"
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#include "narrow.hh"
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namespace openmsx {
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MSXHiResTimer::MSXHiResTimer(const DeviceConfig& config)
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	: MSXDevice(config)
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	, reference(getCurrentTime())
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{
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	reset(getCurrentTime());
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}
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void MSXHiResTimer::reset(EmuTime time)
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{
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	reference.reset(time);
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	latchedValue = 0;
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}
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void MSXHiResTimer::writeIO(uint16_t /*port*/, byte /*value*/, EmuTime time)
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{
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	// write to any port will reset the counter
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	reference.advance(time);
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}
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byte MSXHiResTimer::readIO(uint16_t port, EmuTime time)
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{
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	if ((port & 3) == 0) {
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		// reading port 0 will latch the current counter value
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		latchedValue = reference.getTicksTill(time);
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	}
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	// reading port {0, 1, 2, 3} will read bits {0-7, 8-15, 16-23, 24-32}
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	// of the counter
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	return narrow_cast<byte>(latchedValue >> (8 * (port & 3)));
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}
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byte MSXHiResTimer::peekIO(uint16_t port, EmuTime time) const
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{
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	unsigned tmp = (port & 3) ? latchedValue : reference.getTicksTill(time);
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	return narrow_cast<byte>(tmp >> (8 * (port & 3)));
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}
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template<typename Archive>
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void MSXHiResTimer::serialize(Archive& ar, unsigned /*version*/)
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{
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	ar.template serializeBase<MSXDevice>(*this);
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	ar.serialize("reference",    reference,
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	             "latchedValue", latchedValue);
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}
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INSTANTIATE_SERIALIZE_METHODS(MSXHiResTimer);
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REGISTER_MSXDEVICE(MSXHiResTimer, "HiResTimer");
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} // namespace openmsx