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Reduces number of interrupt-related sequence points.

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This commit is contained in:
Thomas Harte 2021-06-28 19:30:12 -04:00
parent daa0737ce4
commit 919e211bc4
2 changed files with 22 additions and 19 deletions
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34
Machines/Enterprise/Dave.cpp
View File

@ -222,12 +222,7 @@ void TimedInterruptSource::write(uint16_t address, uint8_t value) {
if(rate_ >= InterruptRate::ToneGenerator0) {
programmable_level_ = channels_[int(rate_) - int(InterruptRate::ToneGenerator0)].level;
} else {
// TODO: eliminate copy and paste from below.
switch(rate_) {
case InterruptRate::OnekHz: programmable_offset_ = 125; break;
case InterruptRate::FiftyHz: programmable_offset_ = 2500; break;
default: break;
}
programmable_offset_ = programmble_reload(rate_);
}
}
} break;
@ -240,6 +235,8 @@ void TimedInterruptSource::update_channel(int c, bool is_linked, int decrement)
if(channels_[c].sync) {
channels_[c].value = channels_[c].reload;
} else {
// TODO: the while loop below is far from efficient.
channels_[c].value -= decrement;
while(channels_[c].value < 0) {
channels_[c].value += channels_[c].reload + 1;
@ -276,12 +273,7 @@ void TimedInterruptSource::run_for(Cycles cycles) {
interrupts_ |= uint8_t(Interrupt::VariableFrequency);
}
programmable_level_ ^= true;
switch(rate_) {
case InterruptRate::OnekHz: programmable_offset_ = 125; break;
case InterruptRate::FiftyHz: programmable_offset_ = 2500; break;
default: break;
}
programmable_offset_ = programmble_reload(rate_);
}
}
}
@ -289,15 +281,19 @@ void TimedInterruptSource::run_for(Cycles cycles) {
Cycles TimedInterruptSource::get_next_sequence_point() const {
int result = one_hz_offset_.as<int>();
if(rate_ < InterruptRate::ToneGenerator0) {
result = std::min(result, programmable_offset_);
switch(rate_) {
case InterruptRate::OnekHz:
case InterruptRate::FiftyHz:
result = std::min(result, programmable_offset_);
break;
case InterruptRate::ToneGenerator0:
case InterruptRate::ToneGenerator1: {
const auto& channel = channels_[int(rate_) - int(InterruptRate::ToneGenerator0)];
const int cycles_until_interrupt = (channel.value + 1) + (channel.level ? 0 : channel.reload + 1);
result = std::min(result, cycles_until_interrupt);
} break;
}
// To match normal tone generator logic: the tone generators will
// generate activity when they underflow, not when they hits zero.
result = std::min(result, channels_[0].value + 1);
result = std::min(result, channels_[1].value + 1);
return Cycles(result);
}

7
Machines/Enterprise/Dave.hpp
View File

@ -152,6 +152,13 @@ class TimedInterruptSource {
bool level = false;
} channels_[2];
void update_channel(int c, bool is_linked, int decrement);
static constexpr int programmble_reload(InterruptRate rate) {
switch(rate) {
default: return 0;
case InterruptRate::OnekHz: return 125;
case InterruptRate::FiftyHz: return 2500;
}
}
};
}