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106 lines
2.9 KiB
C++
106 lines
2.9 KiB
C++
#pragma once
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#include "stdafx.h"
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#include "APU.h"
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#include "IMemoryHandler.h"
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#include "ApuEnvelope.h"
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#include "CPU.h"
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#include "Console.h"
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class NoiseChannel : public ApuEnvelope
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{
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private:
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const uint16_t _noisePeriodLookupTableNtsc[16] = { 4, 8, 16, 32, 64, 96, 128, 160, 202, 254, 380, 508, 762, 1016, 2034, 4068 };
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const uint16_t _noisePeriodLookupTablePal[16] = { 4, 8, 14, 30, 60, 88, 118, 148, 188, 236, 354, 472, 708, 944, 1890, 3778 };
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//On power-up, the shift register is loaded with the value 1.
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uint16_t _shiftRegister = 1;
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bool _modeFlag = false;
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bool IsMuted()
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{
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//The mixer receives the current envelope volume except when Bit 0 of the shift register is set, or The length counter is zero
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return (_shiftRegister & 0x01) == 0x01;
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}
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protected:
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void Clock() override
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{
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//Feedback is calculated as the exclusive-OR of bit 0 and one other bit: bit 6 if Mode flag is set, otherwise bit 1.
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bool mode = _console->GetSettings()->CheckFlag(EmulationFlags::DisableNoiseModeFlag) ? false : _modeFlag;
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uint16_t feedback = (_shiftRegister & 0x01) ^ ((_shiftRegister >> (mode ? 6 : 1)) & 0x01);
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_shiftRegister >>= 1;
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_shiftRegister |= (feedback << 14);
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if(IsMuted()) {
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AddOutput(0);
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} else {
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AddOutput(GetVolume());
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}
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}
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public:
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NoiseChannel(AudioChannel channel, shared_ptr<Console> console, SoundMixer* mixer) : ApuEnvelope(channel, console, mixer)
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{
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}
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virtual void Reset(bool softReset) override
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{
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ApuEnvelope::Reset(softReset);
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_period = (GetNesModel() == NesModel::NTSC ? _noisePeriodLookupTableNtsc : _noisePeriodLookupTablePal)[0] - 1;
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_shiftRegister = 1;
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_modeFlag = false;
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}
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virtual void StreamState(bool saving) override
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{
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ApuEnvelope::StreamState(saving);
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Stream(_shiftRegister, _modeFlag);
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}
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void GetMemoryRanges(MemoryRanges &ranges) override
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{
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ranges.AddHandler(MemoryOperation::Write, 0x400C, 0x400F);
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}
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void WriteRAM(uint16_t addr, uint8_t value) override
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{
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_console->GetApu()->Run();
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switch(addr & 0x03) {
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case 0: //400C
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InitializeLengthCounter((value & 0x20) == 0x20);
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InitializeEnvelope(value);
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break;
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case 2: //400E
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_period = (GetNesModel() == NesModel::NTSC ? _noisePeriodLookupTableNtsc : _noisePeriodLookupTablePal)[value & 0x0F] - 1;
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_modeFlag = (value & 0x80) == 0x80;
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break;
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case 3: //400F
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LoadLengthCounter(value >> 3);
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//The envelope is also restarted.
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ResetEnvelope();
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break;
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}
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}
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ApuNoiseState GetState()
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{
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ApuNoiseState state;
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state.Enabled = _enabled;
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state.Envelope = ApuEnvelope::GetState();
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state.Frequency = (double)_console->GetCpu()->GetClockRate(GetNesModel()) / (_period + 1) / (_modeFlag ? 93 : 1);
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state.LengthCounter = ApuLengthCounter::GetState();
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state.ModeFlag = _modeFlag;
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state.OutputVolume = _lastOutput;
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state.Period = _period;
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state.Timer = _timer;
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state.ShiftRegister = _shiftRegister;
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return state;
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}
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}; |