mirror of https://github.com/bsnes-emu/bsnes.git
94 lines
1.9 KiB
C++
94 lines
1.9 KiB
C++
auto APU::Wave::run() -> void {
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if(period && --period == 0) {
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period = 1 * (2048 - frequency);
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pattern_sample = pattern[++pattern_offset];
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}
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uint4 sample = pattern_sample >> volume_shift;
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if(enable == false) sample = 0;
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output = sample;
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}
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auto APU::Wave::clock_length() -> void {
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if(enable && counter) {
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if(++length == 0) enable = false;
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}
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}
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auto APU::Wave::write(uint r, uint8 data) -> void {
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if(r == 0) { //$ff1a NR30
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dac_enable = data & 0x80;
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if(dac_enable == false) enable = false;
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}
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if(r == 1) { //$ff1b NR31
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length = data;
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}
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if(r == 2) { //$ff1c NR32
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switch((data >> 5) & 3) {
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case 0: volume_shift = 4; break; // 0%
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case 1: volume_shift = 0; break; //100%
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case 2: volume_shift = 1; break; // 50%
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case 3: volume_shift = 2; break; // 25%
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}
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}
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if(r == 3) { //$ff1d NR33
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frequency = (frequency & 0x0700) | data;
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}
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if(r == 4) { //$ff1e NR34
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bool initialize = data & 0x80;
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counter = data & 0x40;
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frequency = ((data & 7) << 8) | (frequency & 0x00ff);
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if(initialize) {
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enable = dac_enable;
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period = 1 * (2048 - frequency);
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pattern_offset = 0;
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}
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}
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}
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auto APU::Wave::write_pattern(uint p, uint8 data) -> void {
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p <<= 1;
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pattern[p + 0] = (data >> 4) & 15;
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pattern[p + 1] = (data >> 0) & 15;
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}
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auto APU::Wave::power() -> void {
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enable = 0;
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dac_enable = 0;
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volume_shift = 0;
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frequency = 0;
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counter = 0;
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LinearFeedbackShiftRegisterGenerator r;
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for(auto& n : pattern) n = r() & 15;
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output = 0;
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length = 0;
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period = 0;
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pattern_offset = 0;
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pattern_sample = 0;
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}
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auto APU::Wave::serialize(serializer& s) -> void {
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s.integer(enable);
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s.integer(dac_enable);
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s.integer(volume_shift);
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s.integer(frequency);
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s.integer(counter);
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s.array(pattern);
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s.integer(output);
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s.integer(length);
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s.integer(period);
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s.integer(pattern_offset);
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s.integer(pattern_sample);
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}
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