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Begins addition of interrupt feedback from Nick.

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Also fixes clock rate. Though clearly get_next_sequence_point isn't quite right yet.
This commit is contained in:
Thomas Harte
2021-06-17 22:30:24 -04:00
parent 0c3e9dca28
commit 2fd8a8aa66
3 changed files with 49 additions and 3 deletions
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Machines/Enterprise/Nick.cpp
+22 -1
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@@ -82,7 +82,7 @@ uint8_t Nick::read([[maybe_unused]] uint16_t address) {
return 0xff;
}
void Nick::run_for(HalfCycles duration) {
void Nick::run_for(Cycles duration) {
constexpr int line_length = 912;
int clocks_remaining = duration.as<int>();
@@ -112,8 +112,13 @@ void Nick::run_for(HalfCycles duration) {
++fetch_spot;
}
// TODO: when exactly does the interrupt output change? Am I a window too late? Or two too early?
// Special: set mode as soon as it's known. It'll be needed at the end of HSYNC.
if(window < 2 && fetch_spot >= 2) {
// Set the new interrupt line output.
interrupt_line_ = line_parameters_[1] & 0x80;
// Determine the margins.
left_margin_ = line_parameters_[2] & 0x3f;
right_margin_ = line_parameters_[3] & 0x3f;
@@ -326,6 +331,22 @@ void Nick::flush_pixels() {
allocated_pointer_ = nullptr;
}
// MARK: - Sequence points.
Cycles Nick::get_next_sequence_point() {
// TODO: the below is incorrect; unit test and correct.
// Changing to e.g. Cycles(1) reveals the relevant discrepancy.
// return Cycles(1);
// Any mode line may cause a change in the interrupt output, so as a first blush
// just always report the time until the end of the mode line.
if(lines_remaining_ || horizontal_counter_ >= 2) {
return Cycles(2 + (912 - horizontal_counter_) + (0xff - lines_remaining_) * 912);
} else {
return Cycles(2 - horizontal_counter_);
}
}
// MARK: - CRT passthroughs.
void Nick::set_scan_target(Outputs::Display::ScanTarget *scan_target) {