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Transcribe event times into [mostly] non-action.

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Thomas Harte 2024-12-11 17:32:51 -05:00
parent aed8f8efa8
commit 84d178c0ca
1 changed files with 129 additions and 42 deletions
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171
Machines/Commodore/Plus4/Video.hpp
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@ -68,55 +68,142 @@ public:
// raster lines are from 4 to 203.
//
// The horizontal position register counts 456 dots, 0 to 455.
void run_for(Cycles) {
void run_for(Cycles cycles) {
// Timing:
//
// 456 cycles/line;
// if in PAL mode, divide input clock by 1.25 (?);
// see page 34 of plus4_tech.pdf for event times.
// Horizontal events:
//
// 3: 38-column screen start
// 288: external fetch window end, refresh single clock start, increment character position end
// 290: latch character position to reload
// 296: character window end, character window single clock end, increment refresh start
// 304: video shift register end
// 307: 38-column screen stop
// 315: 40-column screen end
// 328: refresh single clock end
// 336: increment blink, increment refresh end
// 344: horizontal blanking start
// 358: horizontal sync start
// 376: increment vertical line
// 384: burst start, end of screen — clear vertical line, vertical sub and character reload registers
// 390: horizontal sync end
// 408: burst end
// 400: external fetch window start
// 416: horizontal blanking end
// 424: increment character position reload
// 432: character window start, character window single clock start, increment character position start
// 440: video shift register start
// 451: 40-column screen start
auto ticks_remaining = cycles.as<int>() * 8;
while(ticks_remaining--) {
++horizontal_counter_;
switch(horizontal_counter_) {
case 3: // 38-column screen start.
break;
// Vertical events:
//
// 0: attribute fetch start
// 4: vertical screen window start (25 lines)
// 8: vertical screen window start (24 lines)
// 203: attribute fetch end
// 200: vertical screen window stop (24 lines)
// 204: frame window stop, vertical screen window stop (25 lines)
// 226: NTSC vertical blank start
// 229: NTSC vsync start
// 232: NTSC vsync end
// 244: NTSC vertical blank end
// 251: PAL vertical blank start
// 254: PAL vsync start
// 257: PAL vsync end
// 261: end of screen NTSC
// 269: PAL vertical blank end
// 311: end of screen PAL
case 288: // External fetch window end, refresh single clock start, increment character position end.
break;
case 290: // Latch character position to reload.
break;
case 296: // Character window end, character window single clock end, increment refresh start.
break;
case 304: // Video shift register end.
break;
case 307: // 38-column screen stop.
break;
case 315: // 40-column screen end.
break;
case 328: // Refresh single clock end.
break;
case 336: // Increment blink, increment refresh end.
break;
case 344: // Horizontal blanking start.
break;
case 358: // Horizontal sync start.
break;
case 376: // Increment vertical line.
++vertical_counter_;
break;
case 384: // Burst start, end of screen — clear vertical line, vertical sub and character reload registers.
break;
case 390: // Horizontal sync end.
break;
case 408: // Burst end.
break;
case 400: // External fetch window start.
break;
case 416: // Horizontal blanking end.
break;
case 424: // Increment character position reload.
break;
case 432: // Character window start, character window single clock start, increment character position start.
break;
case 440: // Video shift register start.
break;
case 451: // 40-column screen start.
break;
case 465: // Wraparound.
horizontal_counter_ = 0;
break;
}
const auto attribute_fetch_start = []{};
switch(vertical_counter_) {
case 261: // End of screen NTSC. [and hence 0: Attribute fetch start].
if(is_ntsc_) {
vertical_counter_ = 0;
attribute_fetch_start();
}
break;
case 311: // End of screen PAL. [and hence 0: Attribute fetch start].
if(!is_ntsc_) {
vertical_counter_ = 0;
attribute_fetch_start();
}
break;
case 4: // Vertical screen window start (25 lines).
break;
case 8: // Vertical screen window start (24 lines).
break;
case 200: // Vertical screen window stop (24 lines).
break;
case 203: // Attribute fetch end.
break;
case 204: // Vertical screen window stop (25 lines).
break;
case 226: // NTSC vertical blank start.
break;
case 229: // NTSC vsync start.
break;
case 232: // NTSC vsync end.
break;
case 244: // NTSC vertical blank end.
break;
case 251: // PAL vertical blank start.
break;
case 254: // PAL vsync start.
break;
case 257: // PAL vsync end.
break;
case 269: // PAL vertical blank end.
break;
}
}
}
private: