Mesen/Core/TriangleChannel.h
2018-01-01 23:23:18 -05:00

116 lines
2.9 KiB
C++

#pragma once
#include "stdafx.h"
#include "APU.h"
#include "IMemoryHandler.h"
#include "ApuEnvelope.h"
class TriangleChannel : public ApuLengthCounter
{
private:
const uint8_t _sequence[32] = { 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
uint8_t _linearCounter = 0;
uint8_t _linearCounterReload = 0;
bool _linearReloadFlag = false;
bool _linearControlFlag = false;
uint8_t _sequencePosition = 0;
protected:
void Clock() override
{
//The sequencer is clocked by the timer as long as both the linear counter and the length counter are nonzero.
if(_lengthCounter > 0 && _linearCounter > 0) {
_sequencePosition = (_sequencePosition + 1) & 0x1F;
if(_period >= 2 || !EmulationSettings::CheckFlag(EmulationFlags::SilenceTriangleHighFreq)) {
//Disabling the triangle channel when period is < 2 removes "pops" in the audio that are caused by the ultrasonic frequencies
//This is less "accurate" in terms of emulation, so this is an option (disabled by default)
AddOutput(_sequence[_sequencePosition]);
}
}
}
public:
TriangleChannel(AudioChannel channel, SoundMixer* mixer) : ApuLengthCounter(channel, mixer)
{
}
virtual void Reset(bool softReset) override
{
ApuLengthCounter::Reset(softReset);
_linearCounter = 0;
_linearCounterReload = 0;
_linearReloadFlag = false;
_linearControlFlag = false;
_sequencePosition = 0;
}
virtual void StreamState(bool saving) override
{
ApuLengthCounter::StreamState(saving);
Stream(_linearCounter, _linearCounterReload, _linearReloadFlag, _linearControlFlag, _sequencePosition);
}
void GetMemoryRanges(MemoryRanges &ranges) override
{
ranges.AddHandler(MemoryOperation::Write, 0x4008, 0x400B);
}
void WriteRAM(uint16_t addr, uint8_t value) override
{
APU::StaticRun();
switch(addr & 0x03) {
case 0: //4008
_linearControlFlag = (value & 0x80) == 0x80;
_linearCounterReload = value & 0x7F;
InitializeLengthCounter(_linearControlFlag);
break;
case 2: //400A
_period &= ~0x00FF;
_period |= value;
break;
case 3: //400B
LoadLengthCounter(value >> 3);
_period &= ~0xFF00;
_period |= (value & 0x07) << 8;
//Side effects Sets the linear counter reload flag
_linearReloadFlag = true;
break;
}
}
void TickLinearCounter()
{
if(_linearReloadFlag) {
_linearCounter = _linearCounterReload;
} else if(_linearCounter > 0) {
_linearCounter--;
}
if(!_linearControlFlag) {
_linearReloadFlag = false;
}
}
ApuTriangleState GetState()
{
ApuTriangleState state;
state.Enabled = _enabled;
state.Frequency = CPU::GetClockRate(GetNesModel()) / 32.0 / (_period + 1);
state.LengthCounter = ApuLengthCounter::GetState();
state.OutputVolume = _lastOutput;
state.Period = _period;
state.Timer = _timer;
state.SequencePosition = _sequencePosition;
return state;
}
};