mirror of https://github.com/bsnes-emu/bsnes.git
86 lines
3.2 KiB
C++
86 lines
3.2 KiB
C++
//this should only be called by CPU::PPUcounter::tick();
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//keeps track of previous counter positions in history table
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void PPUcounter::tick() {
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status.hcounter += 2; //increment by smallest unit of time
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if(status.hcounter >= 1360 && status.hcounter == lineclocks()) {
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status.hcounter = 0;
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vcounter_tick();
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}
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history.index = (history.index + 1) & 2047;
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history.field [history.index] = status.field;
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history.vcounter[history.index] = status.vcounter;
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history.hcounter[history.index] = status.hcounter;
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}
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//this should only be called by PPU::PPUcounter::tick(n);
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//allows stepping by more than the smallest unit of time
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void PPUcounter::tick(unsigned clocks) {
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status.hcounter += clocks;
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if(status.hcounter >= lineclocks()) {
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status.hcounter -= lineclocks();
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vcounter_tick();
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}
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}
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//internal
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void PPUcounter::vcounter_tick() {
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if(++status.vcounter == 128) status.interlace = ppu.interlace();
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if((system.region() == System::Region::NTSC && status.interlace == false && status.vcounter == 262)
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|| (system.region() == System::Region::NTSC && status.interlace == true && status.vcounter == 263)
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|| (system.region() == System::Region::NTSC && status.interlace == true && status.vcounter == 262 && status.field == 1)
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|| (system.region() == System::Region::PAL && status.interlace == false && status.vcounter == 312)
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|| (system.region() == System::Region::PAL && status.interlace == true && status.vcounter == 313)
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|| (system.region() == System::Region::PAL && status.interlace == true && status.vcounter == 312 && status.field == 1)
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) {
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status.vcounter = 0;
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status.field = !status.field;
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}
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if(scanline) scanline();
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}
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bool PPUcounter::field () const { return status.field; }
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uint16 PPUcounter::vcounter() const { return status.vcounter; }
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uint16 PPUcounter::hcounter() const { return status.hcounter; }
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bool PPUcounter::field (unsigned offset) const { return history.field [(history.index - (offset >> 1)) & 2047]; }
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uint16 PPUcounter::vcounter(unsigned offset) const { return history.vcounter[(history.index - (offset >> 1)) & 2047]; }
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uint16 PPUcounter::hcounter(unsigned offset) const { return history.hcounter[(history.index - (offset >> 1)) & 2047]; }
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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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//
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//dot 323 range = { 1292, 1294, 1296 }
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//dot 327 range = { 1310, 1312, 1314 }
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uint16 PPUcounter::hdot() const {
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if(system.region() == System::Region::NTSC && status.interlace == false && vcounter() == 240 && field() == 1) {
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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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uint16 PPUcounter::lineclocks() const {
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if(system.region() == System::Region::NTSC && status.interlace == false && vcounter() == 240 && field() == 1) return 1360;
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return 1364;
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}
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void PPUcounter::reset() {
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status.interlace = false;
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status.field = 0;
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status.vcounter = 0;
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status.hcounter = 0;
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history.index = 0;
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for(unsigned i = 0; i < 2048; i++) {
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history.field [i] = 0;
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history.vcounter[i] = 0;
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history.hcounter[i] = 0;
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}
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}
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