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Adds a delay on vsync visibility (i.e. as to generating an interrupt).

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This commit is contained in:
Thomas Harte 2019-12-29 19:03:08 -05:00
parent 47068ee081
commit 8ce26e7182
2 changed files with 14 additions and 4 deletions
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14
Machines/Atari/ST/Video.cpp
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@ -99,13 +99,13 @@ const int vsync_x_position = CYCLE(56); // Horizontal cycle on which vertical s
const int hsync_start = CYCLE(48); // Cycles before end of line when hsync starts.
const int hsync_end = CYCLE(8); // Cycles before end of line when hsync ends.
const int hsync_delay_period = hsync_end; // Signal hsync at the end of the line.
const int hsync_delay_period = hsync_end; // Signal hsync at the end of the line.
const int vsync_delay_period = hsync_delay_period; // Signal vsync with the same delay as hsync.
// "VSYNC starts 104 cycles after the start of the previous line's HSYNC, so that's 4 cycles before DE would be activated. ";
// that's an inconsistent statement since it would imply VSYNC at +54, which is 2 cycles before DE in 60Hz mode and 6 before
// in 50Hz mode. I've gone with 56, to be four cycles ahead of DE in 50Hz mode.
//
// TODO: some sort of latency on vsync and hsync visibility, I would imagine?
}
@ -183,6 +183,7 @@ void Video::advance(HalfCycles duration) {
const int run_length = std::min(integer_duration, next_event - x_);
const bool display_enable = vertical_.enable && horizontal_.enable;
const bool hsync = horizontal_.sync;
const bool vsync = vertical_.sync;
// Ensure proper fetching irrespective of the output.
if(load_) {
@ -339,6 +340,11 @@ void Video::advance(HalfCycles duration) {
// Schedule change in outwardly-visible hsync line.
add_event(hsync_delay_period - integer_duration, horizontal_.sync ? Event::Type::SetHsync : Event::Type::ResetHsync);
}
if(vertical_.sync != vsync) {
// Schedule change in outwardly-visible hsync line.
add_event(vsync_delay_period - integer_duration, horizontal_.sync ? Event::Type::SetVsync : Event::Type::ResetVsync);
}
}
}
@ -364,7 +370,7 @@ bool Video::hsync() {
}
bool Video::vsync() {
return vertical_.sync;
return public_state_.vsync;
}
bool Video::display_enabled() {

4
Machines/Atari/ST/Video.hpp
View File

@ -228,6 +228,7 @@ class Video {
struct PublicState {
bool display_enable = false;
bool hsync = false;
bool vsync = false;
} public_state_;
struct Event {
@ -235,6 +236,7 @@ class Video {
enum class Type {
SetDisplayEnable, ResetDisplayEnable,
SetHsync, ResetHsync,
SetVsync, ResetVsync,
} type;
Event(Type type, int delay) : delay(delay), type(type) {}
@ -250,6 +252,8 @@ class Video {
case Type::ResetDisplayEnable: state.display_enable = false; break;
case Type::SetHsync: state.hsync = true; break;
case Type::ResetHsync: state.hsync = false; break;
case Type::SetVsync: state.vsync = true; break;
case Type::ResetVsync: state.vsync = false; break;
}
}
};