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Interupts 1kHz and 50Hz interrupts, while edging towards tone generator interrupts.

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This commit is contained in:
Thomas Harte 2021-06-27 22:08:38 -04:00
parent e4a650aaff
commit 116e0f0105
2 changed files with 22 additions and 5 deletions
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22
Machines/Enterprise/Dave.cpp
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@ -214,6 +214,8 @@ void TimedInterruptSource::write(uint16_t address, uint8_t value) {
case 7:
channels_[0].sync = value & 0x01;
channels_[1].sync = value & 0x02;
// TODO: a hard cut-over here if switching to tracking a tone generator.
rate_ = InterruptRate((value >> 5) & 3);
break;
}
@ -227,10 +229,24 @@ void TimedInterruptSource::run_for(Cycles cycles) {
one_hz_offset_ += clock_rate;
}
// TODO: update the programmable-frequency interrupt.
// TODO: shadow update the two tone channels.
// Update the programmable-frequency interrupt.
programmable_offset_ -= cycles.as<int>();
if(programmable_offset_ < 0) {
interrupts_ |= uint8_t(Interrupt::VariableFrequency);
switch(rate_) {
case InterruptRate::OnekHz: programmable_offset_ = 249; break;
case InterruptRate::FiftyHz: programmable_offset_ = 4999; break;
case InterruptRate::ToneGenerator0: programmable_offset_ = channels_[0].value; break;
case InterruptRate::ToneGenerator1: programmable_offset_ = channels_[1].value; break;
}
}
}
Cycles TimedInterruptSource::get_next_sequence_point() const {
// TODO: support the programmable-frequency interrupt.
return one_hz_offset_;
// To match normal tone generator logic: the programmable timer will
// generate activity when it underflows, not when it hits zero.
return (programmable_offset_+1) < one_hz_offset_.as<int>() ? Cycles(programmable_offset_+1) : one_hz_offset_;
}

5
Machines/Enterprise/Dave.hpp
View File

@ -133,6 +133,7 @@ class TimedInterruptSource {
static constexpr Cycles clock_rate{250000};
Cycles one_hz_offset_ = clock_rate;
uint16_t programmable_offset_ = 0;
enum class InterruptRate {
OnekHz,
@ -142,8 +143,8 @@ class TimedInterruptSource {
} rate_ = InterruptRate::OnekHz;
struct Channel {
uint16_t value, reload;
bool sync;
uint16_t value = 100, reload = 100;
bool sync = false;
} channels_[2];
};