115 lines
2.1 KiB
C#
115 lines
2.1 KiB
C#
using System.IO;
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namespace MyNes.Core
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{
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internal class VRC6Sawtooth
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{
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private byte AccumRate;
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private int accumClock;
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private byte accumulationRegister;
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private int frequency;
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private int freqTimer;
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private int cycles;
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private bool enabled;
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internal int output;
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internal bool Outputable;
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internal void HardReset()
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{
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}
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private void UpdateFrequency()
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{
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freqTimer = (frequency + 1) * 2;
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}
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internal void Write0(ref byte data)
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{
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AccumRate = (byte)(data & 0x3Fu);
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}
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internal void Write1(ref byte data)
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{
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frequency = (frequency & 0xF00) | data;
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UpdateFrequency();
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}
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internal void Write2(ref byte data)
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{
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frequency = (frequency & 0xFF) | ((data & 0xF) << 8);
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enabled = (data & 0x80) == 128;
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UpdateFrequency();
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}
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internal void ClockSingle()
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{
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if (--cycles > 0)
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{
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return;
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}
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cycles = freqTimer;
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if (enabled)
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{
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accumClock++;
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switch (++accumClock)
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{
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case 2:
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case 4:
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case 6:
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case 8:
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case 10:
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case 12:
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accumulationRegister += AccumRate;
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break;
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case 14:
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accumulationRegister = 0;
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accumClock = 0;
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break;
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}
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if (Outputable)
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{
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output = (accumulationRegister >> 3) & 0x1F;
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}
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else
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{
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output = 0;
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}
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}
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else
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{
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output = 0;
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}
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}
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internal void SaveState(ref BinaryWriter stream)
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{
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stream.Write(AccumRate);
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stream.Write(accumClock);
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stream.Write(accumulationRegister);
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stream.Write(frequency);
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stream.Write(freqTimer);
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stream.Write(cycles);
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stream.Write(enabled);
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}
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internal void LoadState(ref BinaryReader stream)
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{
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AccumRate = stream.ReadByte();
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accumClock = stream.ReadInt32();
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accumulationRegister = stream.ReadByte();
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frequency = stream.ReadInt32();
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freqTimer = stream.ReadInt32();
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cycles = stream.ReadInt32();
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enabled = stream.ReadBoolean();
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}
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}
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}
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