mirror of https://github.com/bsnes-emu/bsnes.git
49 lines
1.1 KiB
C++
49 lines
1.1 KiB
C++
//counter_rate = number of samples per counter event
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//all rates are evenly divisible by counter_range (0x7800, 30720, or 2048 * 5 * 3)
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//note that rate[0] is a special case, which never triggers
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const uint16 DSP::CounterRate[32] = {
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0, 2048, 1536,
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1280, 1024, 768,
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640, 512, 384,
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320, 256, 192,
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160, 128, 96,
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80, 64, 48,
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40, 32, 24,
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20, 16, 12,
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10, 8, 6,
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5, 4, 3,
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2,
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1,
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};
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//counter_offset = counter offset from zero
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//counters do not appear to be aligned at zero for all rates
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const uint16 DSP::CounterOffset[32] = {
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0, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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536, 0, 1040,
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0,
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0,
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};
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inline auto DSP::counterTick() -> void {
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state.counter--;
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if(state.counter < 0) state.counter = CounterRange - 1;
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}
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//return true if counter event should trigger
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inline auto DSP::counterPoll(unsigned rate) -> bool {
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if(rate == 0) return false;
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return (((unsigned)state.counter + CounterOffset[rate]) % CounterRate[rate]) == 0;
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}
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