MSXHiResTimer.cc

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#include "MSXHiResTimer.hh"
#include "narrow.hh"
#include "serialize.hh"
 
namespace openmsx {
 
MSXHiResTimer::MSXHiResTimer(const DeviceConfig& config)
        : MSXDevice(config)
        , reference(getCurrentTime())
{
        reset(getCurrentTime());
}
 
void MSXHiResTimer::reset(EmuTime::param time)
{
        reference.reset(time);
        latchedValue = 0;
}
 
void MSXHiResTimer::writeIO(word /*port*/, byte /*value*/, EmuTime::param time)
{
        // write to any port will reset the counter
        reference.advance(time);
}
 
byte MSXHiResTimer::readIO(word port, EmuTime::param time)
{
        if ((port & 3) == 0) {
                // reading port 0 will latch the current counter value
                latchedValue = reference.getTicksTill(time);
        }
        // reading port {0, 1, 2, 3} will read bits {0-7, 8-15, 16-23, 24-32}
        // of the counter
        return narrow_cast<byte>(latchedValue >> (8 * (port & 3)));
}
 
byte MSXHiResTimer::peekIO(word port, EmuTime::param time) const
{
        unsigned tmp = (port & 3) ? latchedValue : reference.getTicksTill(time);
        return narrow_cast<byte>(tmp >> (8 * (port & 3)));
}
 
template<typename Archive>
void MSXHiResTimer::serialize(Archive& ar, unsigned /*version*/)
{
        ar.template serializeBase<MSXDevice>(*this);
        ar.serialize("reference",    reference,
                     "latchedValue", latchedValue);
}
INSTANTIATE_SERIALIZE_METHODS(MSXHiResTimer);
REGISTER_MSXDEVICE(MSXHiResTimer, "HiResTimer");
 
} // namespace openmsx