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Introduces a latency between DE and load.

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This commit is contained in:
Thomas Harte 2019-12-10 21:24:15 -05:00
parent 768b3709b8
commit 0a405d1c06
2 changed files with 31 additions and 9 deletions
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37
Machines/Atari/ST/Video.cpp
View File

@ -145,6 +145,7 @@ void Video::run_for(HalfCycles duration) {
if(horizontal_timings.set_blank > x_) next_event = std::min(next_event, horizontal_timings.set_blank);
if(horizontal_timings.reset_enable > x_) next_event = std::min(next_event, horizontal_timings.reset_enable);
if(horizontal_timings.set_enable > x_) next_event = std::min(next_event, horizontal_timings.set_enable);
if(next_load_toggle_ > x_) next_event = std::min(next_event, next_load_toggle_);
// Check for events that are relative to existing latched state.
if(line_length_ - 50*2 > x_) next_event = std::min(next_event, line_length_ - 50*2);
@ -163,14 +164,16 @@ void Video::run_for(HalfCycles duration) {
shifter_.output_sync(run_length);
} else if(horizontal_.blank || vertical_.blank) {
shifter_.output_blank(run_length);
} else if(!vertical_.enable || !horizontal_.enable) {
} else if(!load_) {
shifter_.output_border(run_length, output_bpp_);
} else {
const int since_load = x_ - load_base_;
// There will be pixels this line, subject to the shifter pipeline.
// Divide into 8-[half-]cycle windows; at the start of each window fetch a word,
// and during the rest of the window, shift out.
int start_column = x_ >> 3;
const int end_column = (x_ + run_length) >> 3;
int start_column = since_load >> 3;
const int end_column = (since_load + run_length) >> 3;
// Rules obeyed below:
//
@ -182,9 +185,9 @@ void Video::run_for(HalfCycles duration) {
shifter_.output_pixels(run_length, output_bpp_);
} else {
// Continue the current column if partway across.
if(x_&7) {
if(since_load&7) {
// If at least one column boundary is crossed, complete this column.
shifter_.output_pixels(8 - (x_ & 7), output_bpp_);
shifter_.output_pixels(8 - (since_load & 7), output_bpp_);
++start_column; // This starts a new column, so latch a new word.
latch_word();
}
@ -197,8 +200,8 @@ void Video::run_for(HalfCycles duration) {
}
// Output the start of the next column, if necessary.
if((x_ + run_length) & 7) {
shifter_.output_pixels((x_ + run_length) & 7, output_bpp_);
if((since_load + run_length) & 7) {
shifter_.output_pixels((since_load + run_length) & 7, output_bpp_);
}
}
}
@ -248,8 +251,20 @@ void Video::run_for(HalfCycles duration) {
else if(horizontal_timings.set_blank == x_) horizontal_.blank = true;
else if(horizontal_timings.reset_enable == x_) horizontal_.enable = false;
else if(horizontal_timings.set_enable == x_) horizontal_.enable = true;
else if(line_length_ - 50*2 == x_) horizontal_.sync = true;
else if(line_length_ - 50*2 == x_) { horizontal_.sync = true; horizontal_.enable = false; }
else if(line_length_ - 10*2 == x_) horizontal_.sync = false;
else if(next_load_toggle_ == x_) {
next_load_toggle_ = -1;
load_ ^= true;
load_base_ = x_;
}
// Check for an upcoming load toggle — that is, a time at which load_ will be either
// disabled or enabled. These are scheduled for four cycles after the event that should
// change load has occurred.
if((horizontal_.enable && vertical_.enable) != load_ && next_load_toggle_ == -1) {
next_load_toggle_ = x_ + 8; // 4 cycles = 8 half-cycles
}
// Check vertical events.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && x_ == vsync_x_position) {
@ -406,6 +421,8 @@ void Video::write(int address, uint16_t value) {
}
void Video::update_output_mode() {
// const auto old_frequency = field_frequency_;
// If this is black and white mode, that's that.
switch((video_mode_ >> 8) & 3) {
case 0: output_bpp_ = OutputBpp::Four; break;
@ -416,10 +433,12 @@ void Video::update_output_mode() {
case 2:
output_bpp_ = OutputBpp::One;
field_frequency_ = FieldFrequency::SeventyTwo;
// if(field_frequency_ != old_frequency) {
// printf("%d, %d -> %d\n", x_, y_, field_frequency_);
// }
return;
}
// const auto old_frequency = field_frequency_;
field_frequency_ = (sync_mode_ & 0x200) ? FieldFrequency::Fifty : FieldFrequency::Sixty;
// if(field_frequency_ != old_frequency) {
// printf("%d, %d -> %d\n", x_, y_, field_frequency_);

3
Machines/Atari/ST/Video.hpp
View File

@ -116,6 +116,9 @@ class Video {
uint16_t line_buffer_[256];
int x_ = 0, y_ = 0, next_y_ = 0;
int next_load_toggle_ = -1;
bool load_ = false;
int load_base_ = 0;
uint16_t video_mode_ = 0;
uint16_t sync_mode_ = 0;