mirror of
https://github.com/Marat-Tanalin/bsnes-mt.git
synced 2025-04-02 10:21:42 -04:00
84 lines
2.7 KiB
C++
84 lines
2.7 KiB
C++
auto PPUcounter::tick() -> void {
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time.hcounter += 2; //increment by smallest unit of time.
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if(time.hcounter == hperiod()) {
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last.hperiod = hperiod();
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time.hcounter = 0;
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tickScanline();
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}
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}
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auto PPUcounter::tick(uint clocks) -> void {
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time.hcounter += clocks;
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if(time.hcounter >= hperiod()) {
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last.hperiod = hperiod();
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time.hcounter -= hperiod();
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tickScanline();
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}
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}
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auto PPUcounter::tickScanline() -> void {
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if(++time.vcounter == 128) {
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//it's not important when this is captured: it is only needed at V=240 or V=311.
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time.interlace = ppu.interlace();
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time.vperiod += interlace() && !field();
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}
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if(vcounter() == vperiod()) {
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last.vperiod = vperiod();
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//this may be off by one until V=128, hence why vperiod() is a private function.
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time.vperiod = Region::NTSC() ? 262 : 312;
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time.vcounter = 0;
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time.field ^= 1;
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}
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time.hperiod = 1364;
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//NTSC and PAL scanline rates would not match up with color clocks if every scanline were 1364 clocks.
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//to offset for this error, NTSC has one short scanline, and PAL has one long scanline.
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if(Region::NTSC() && interlace() == 0 && field() == 1 && vcounter() == 240) time.hperiod -= 4;
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if(Region::PAL() && interlace() == 1 && field() == 1 && vcounter() == 311) time.hperiod += 4;
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if(scanline) scanline();
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}
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auto PPUcounter::interlace() const -> bool { return time.interlace; }
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auto PPUcounter::field() const -> bool { return time.field; }
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auto PPUcounter::vcounter() const -> uint { return time.vcounter; }
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auto PPUcounter::hcounter() const -> uint { return time.hcounter; }
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auto PPUcounter::vperiod() const -> uint { return time.vperiod; }
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auto PPUcounter::hperiod() const -> uint { return time.hperiod; }
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auto PPUcounter::vcounter(uint offset) const -> uint {
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if(offset <= hcounter()) return vcounter();
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if(vcounter() > 0) return vcounter() - 1;
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return last.vperiod - 1;
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}
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auto PPUcounter::hcounter(uint offset) const -> uint {
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if(offset <= hcounter()) return hcounter() - offset;
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return hcounter() + last.hperiod - offset;
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}
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//one PPU dot = 4 CPU clocks.
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//
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//PPU dots 323 and 327 are 6 CPU clocks long.
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//this does not apply to NTSC non-interlace scanline 240 on odd fields. this is
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//because the PPU skips one dot to alter the color burst phase of the video signal.
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//it is not known what happens for PAL 1368 clock scanlines.
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//
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//dot 323 range = {1292, 1294, 1296}
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//dot 327 range = {1310, 1312, 1314}
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auto PPUcounter::hdot() const -> uint {
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if(hperiod() == 1360) {
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return hcounter() >> 2;
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} else {
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return hcounter() - ((hcounter() > 1292) << 1) - ((hcounter() > 1310) << 1) >> 2;
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}
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}
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auto PPUcounter::reset() -> void {
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time = {};
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last = {};
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time.vperiod = last.vperiod = Region::NTSC() ? 262 : 312;
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time.hperiod = last.hperiod = 1364;
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}
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