furnace/src/engine/platform/ym2610shared.h

static unsigned short chanOffs[4]={
  0x01, 0x02, 0x101, 0x102
};
static unsigned short opOffs[4]={
  0x00, 0x04, 0x08, 0x0c
};
static bool isOutput[8][4]={
  // 1     3     2    4
  {false,false,false,true},
  {false,false,false,true},
  {false,false,false,true},
  {false,false,false,true},
  {false,false,true ,true},
  {false,true ,true ,true},
  {false,true ,true ,true},
  {true ,true ,true ,true},
};
static unsigned char dtTable[8]={
  7,6,5,0,1,2,3,0
};

static int orderedOps[4]={
  0,2,1,3
};

#define rWrite(a,v) if (!skipRegisterWrites) {pendingWrites[a]=v;}
#define immWrite(a,v) if (!skipRegisterWrites) {writes.emplace(a,v);}

#define FM_FREQ_BASE 622.0f
#define PSG_FREQ_BASE 7640.0f