mirror of https://github.com/bsnes-emu/bsnes.git
138 lines
3.0 KiB
C++
138 lines
3.0 KiB
C++
auto APU::Square2::dacEnable() const -> bool {
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return (envelopeVolume || envelopeDirection);
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}
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auto APU::Square2::run() -> void {
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if(period && --period == 0) {
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period = 2 * (2048 - frequency);
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phase++;
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switch(duty) {
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case 0: dutyOutput = (phase == 6); break; //______-_
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case 1: dutyOutput = (phase >= 6); break; //______--
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case 2: dutyOutput = (phase >= 4); break; //____----
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case 3: dutyOutput = (phase <= 5); break; //------__
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}
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}
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uint4 sample = dutyOutput ? (uint)volume : 0;
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if(!enable) sample = 0;
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output = sample;
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}
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auto APU::Square2::clockLength() -> void {
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if(counter) {
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if(length && --length == 0) enable = false;
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}
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}
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auto APU::Square2::clockEnvelope() -> void {
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if(enable && envelopeFrequency && --envelopePeriod == 0) {
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envelopePeriod = envelopeFrequency ? (uint)envelopeFrequency : 8;
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if(envelopeDirection == 0 && volume > 0) volume--;
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if(envelopeDirection == 1 && volume < 15) volume++;
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}
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}
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auto APU::Square2::read(uint16 addr) -> uint8 {
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if(addr == 0xff15) { //NR20
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return 0xff;
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}
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if(addr == 0xff16) { //NR21
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return duty << 6 | 0x3f;
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}
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if(addr == 0xff17) { //NR22
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return envelopeVolume << 4 | envelopeDirection << 3 | envelopeFrequency;
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}
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if(addr == 0xff18) { //NR23
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return 0xff;
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}
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if(addr == 0xff19) { //NR24
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return 0x80 | counter << 6 | 0x3f;
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}
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return 0xff;
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}
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auto APU::Square2::write(uint16 addr, uint8 data) -> void {
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if(addr == 0xff16) { //NR21
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duty = data.bits(7,6);
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length = 64 - data.bits(5,0);
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}
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if(addr == 0xff17) { //NR22
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envelopeVolume = data.bits(7,4);
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envelopeDirection = data.bit (3);
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envelopeFrequency = data.bits(2,0);
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if(!dacEnable()) enable = false;
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}
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if(addr == 0xff18) { //NR23
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frequency.bits(7,0) = data;
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}
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if(addr == 0xff19) { //NR24
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if(apu.phase.bit(0) && !counter && data.bit(6)) {
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if(length && --length == 0) enable = false;
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}
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counter = data.bit(6);
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frequency.bits(10,8) = data.bits(2,0);
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if(data.bit(7)) {
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enable = dacEnable();
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period = 2 * (2048 - frequency);
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envelopePeriod = envelopeFrequency ? (uint)envelopeFrequency : 8;
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volume = envelopeVolume;
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if(!length) {
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length = 64;
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if(apu.phase.bit(0) && counter) length--;
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}
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}
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}
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}
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auto APU::Square2::power(bool initializeLength) -> void {
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enable = 0;
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duty = 0;
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envelopeVolume = 0;
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envelopeDirection = 0;
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envelopeFrequency = 0;
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frequency = 0;
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counter = 0;
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output = 0;
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dutyOutput = 0;
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phase = 0;
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period = 0;
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envelopePeriod = 0;
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volume = 0;
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if(initializeLength) length = 64;
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}
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auto APU::Square2::serialize(serializer& s) -> void {
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s.integer(enable);
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s.integer(duty);
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s.integer(length);
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s.integer(envelopeVolume);
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s.integer(envelopeDirection);
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s.integer(envelopeFrequency);
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s.integer(frequency);
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s.integer(counter);
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s.integer(output);
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s.integer(dutyOutput);
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s.integer(phase);
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s.integer(period);
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s.integer(envelopePeriod);
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s.integer(volume);
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}
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