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Merge pull request #916 from TomHarte/OffByOne

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Corrects off-by-one timing errors in the ZX Spectrum.
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Thomas Harte 2021-04-18 20:25:13 -04:00 committed by GitHub
commit 76370d9418
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2 changed files with 6 additions and 6 deletions
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6
Machines/Sinclair/ZXSpectrum/Video.hpp
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@ -98,7 +98,7 @@ template <VideoTiming timing> class Video {
.contention_duration = 129 * 2,
// i.e. interrupt is first signalled 14368 cycles before the first video fetch.
.interrupt_time = (228*311 - 14360) * 2,
.interrupt_time = (1 + 228*311 - 14365 - 5) * 2,
.delays = { // Should start at 14365
2, 1,
@ -123,7 +123,7 @@ template <VideoTiming timing> class Video {
.contention_leadin = 4 * 2,
.contention_duration = 128 * 2,
.interrupt_time = (228*311 - 14357) * 2,
.interrupt_time = (1 + 228*311 - 14361 - 4) * 2,
.delays = { // Should start at 14361.
12, 11,
@ -148,7 +148,7 @@ template <VideoTiming timing> class Video {
.contention_leadin = 4 * 2,
.contention_duration = 128 * 2,
.interrupt_time = (224*312 - 14331) * 2,
.interrupt_time = (1 + 224*312 - 14335 - 4) * 2,
.delays = { // Should start at 14335.
12, 11,

6
Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
View File

@ -245,7 +245,7 @@ template<Model model> class ConcreteMachine:
// always occurs if it is in the $4000–$8000 range regardless of current
// memory mapping.
HalfCycles delay;
HalfCycles time = video_.time_since_flush() + HalfCycles(1);
HalfCycles time = video_.time_since_flush();
if((address & 0xc000) == 0x4000) {
for(int c = 0; c < ((address & 1) ? 4 : 2); c++) {
@ -269,7 +269,7 @@ template<Model model> class ConcreteMachine:
// These all start by loading the address bus, then set MREQ
// half a cycle later.
if(is_contended_[address >> 14]) {
const HalfCycles delay = video_.last_valid()->access_delay(video_.time_since_flush() + HalfCycles(1));
const HalfCycles delay = video_.last_valid()->access_delay(video_.time_since_flush());
advance(cycle.length + delay);
return delay;
@ -284,7 +284,7 @@ template<Model model> class ConcreteMachine:
const auto half_cycles = cycle.length.as<int>();
assert(!(half_cycles & 1));
HalfCycles time = video_.time_since_flush() + HalfCycles(1);
HalfCycles time = video_.time_since_flush();
HalfCycles delay;
for(int c = 0; c < half_cycles; c += 2) {
const auto next_delay = video_.last_valid()->access_delay(time);