mirror of https://github.com/bsnes-emu/bsnes.git
54 lines
1.3 KiB
C++
54 lines
1.3 KiB
C++
auto CPU::timer_step(unsigned clocks) -> void {
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for(unsigned c = 0; c < clocks; c++) {
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for(unsigned n = 0; n < 4; n++) {
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auto& timer = regs.timer[n];
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if(timer.pending) {
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timer.pending = false;
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if(timer.control.enable == 1) {
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timer.period = timer.reload;
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}
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continue;
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}
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if(timer.control.enable == false || timer.control.cascade == true) continue;
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static unsigned mask[] = {0, 63, 255, 1023};
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if((regs.clock & mask[timer.control.frequency]) == 0) {
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timer_increment(n);
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}
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}
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regs.clock++;
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}
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}
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auto CPU::timer_increment(unsigned n) -> void {
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auto& timer = regs.timer[n];
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if(++timer.period == 0) {
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timer.period = timer.reload;
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if(timer.control.irq) regs.irq.flag.timer[n] = 1;
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if(apu.fifo[0].timer == n) timer_fifo_run(0);
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if(apu.fifo[1].timer == n) timer_fifo_run(1);
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if(n < 3 && regs.timer[n + 1].control.enable && regs.timer[n + 1].control.cascade) {
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timer_increment(n + 1);
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}
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}
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}
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auto CPU::timer_fifo_run(unsigned n) -> void {
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apu.fifo[n].read();
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if(apu.fifo[n].size > 16) return;
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auto& dma = regs.dma[1 + n];
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if(dma.control.enable && dma.control.timingmode == 3) {
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dma.pending = true;
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dma.control.targetmode = 2;
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dma.control.size = 1;
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dma.run.length = 4;
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}
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}
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