#include "../copyright"

#include "snes9x.h"
#include "ppu.h"
#include "cpuexec.h"

#include "sa1.h"

static void S9xSA1CharConv2(void);
static void S9xSA1DMA(void);
static void S9xSA1ReadVariableLengthData(bool inc, bool no_shift);

void S9xSA1Init()
{
   SA1.NMIActive = false;
   SA1.IRQActive = 0;
   SA1.WaitingForInterrupt = false;
   SA1.Waiting = false;
   SA1.Flags = 0;
   SA1.Executing = false;
   memset(&Memory.FillRAM [0x2200], 0, 0x200);
   Memory.FillRAM [0x2200] = 0x20;
   Memory.FillRAM [0x2220] = 0x00;
   Memory.FillRAM [0x2221] = 0x01;
   Memory.FillRAM [0x2222] = 0x02;
   Memory.FillRAM [0x2223] = 0x03;
   Memory.FillRAM [0x2228] = 0xff;
   SA1.op1 = 0;
   SA1.op2 = 0;
   SA1.arithmetic_op = 0;
   SA1.sum = 0;
   SA1.overflow = false;
   SA1.S9xOpcodes = NULL;
}

void S9xSA1Reset()
{
   SA1.Registers.PB = 0;
   SA1.Registers.PC = Memory.FillRAM [0x2203] | (Memory.FillRAM [0x2204] << 8);
   SA1.Registers.D.W = 0;
   SA1.Registers.DB = 0;
   SA1.Registers.SH = 1;
   SA1.Registers.SL = 0xFF;
   SA1.Registers.XH = 0;
   SA1.Registers.YH = 0;
   SA1.Registers.P.W = 0;

   SA1.ShiftedPB = 0;
   SA1.ShiftedDB = 0;
   SA1SetFlags(MemoryFlag | IndexFlag | IRQ | Emulation);
   SA1ClearFlags(Decimal);

   SA1.WaitingForInterrupt = false;
   SA1.PC = NULL;
   SA1.PCBase = NULL;
   S9xSA1SetPCBase(SA1.Registers.PC);
   SA1.S9xOpcodes = S9xSA1OpcodesM1X1;

   S9xSA1UnpackStatus();
   S9xSA1FixCycles();
   SA1.Executing = true;
   SA1.BWRAM = Memory.SRAM;
   Memory.FillRAM [0x2225] = 0;
}

void S9xSA1SetBWRAMMemMap(uint8_t val)
{
   int32_t c;

   if (val & 0x80)
   {
      for (c = 0; c < 0x400; c += 16)
      {
         SA1.Map [c + 6] = SA1.Map [c + 0x806] = (uint8_t*) MAP_BWRAM_BITMAP2;
         SA1.Map [c + 7] = SA1.Map [c + 0x807] = (uint8_t*) MAP_BWRAM_BITMAP2;
         SA1.WriteMap [c + 6] = SA1.WriteMap [c + 0x806] = (uint8_t*) MAP_BWRAM_BITMAP2;
         SA1.WriteMap [c + 7] = SA1.WriteMap [c + 0x807] = (uint8_t*) MAP_BWRAM_BITMAP2;
      }
      SA1.BWRAM = Memory.SRAM + (val & 0x7f) * 0x2000 / 4;
   }
   else
   {
      for (c = 0; c < 0x400; c += 16)
      {
         SA1.Map [c + 6] = SA1.Map [c + 0x806] = (uint8_t*) MAP_BWRAM;
         SA1.Map [c + 7] = SA1.Map [c + 0x807] = (uint8_t*) MAP_BWRAM;
         SA1.WriteMap [c + 6] = SA1.WriteMap [c + 0x806] = (uint8_t*) MAP_BWRAM;
         SA1.WriteMap [c + 7] = SA1.WriteMap [c + 0x807] = (uint8_t*) MAP_BWRAM;
      }
      SA1.BWRAM = Memory.SRAM + (val & 7) * 0x2000;
   }
}

void S9xFixSA1AfterSnapshotLoad()
{
   SA1.ShiftedPB = (uint32_t) SA1.Registers.PB << 16;
   SA1.ShiftedDB = (uint32_t) SA1.Registers.DB << 16;

   S9xSA1SetPCBase(SA1.ShiftedPB + SA1.Registers.PC);
   S9xSA1UnpackStatus();
   S9xSA1FixCycles();
   SA1.VirtualBitmapFormat = (Memory.FillRAM [0x223f] & 0x80) ? 2 : 4;
   Memory.BWRAM = Memory.SRAM + (Memory.FillRAM [0x2224] & 7) * 0x2000;
   S9xSA1SetBWRAMMemMap(Memory.FillRAM [0x2225]);

   SA1.Waiting = (Memory.FillRAM [0x2200] & 0x60) != 0;
   SA1.Executing = !SA1.Waiting;
}

uint8_t S9xSA1GetByte(uint32_t address)
{
   uint8_t* GetAddress = SA1.Map [(address >> MEMMAP_SHIFT) & MEMMAP_MASK];
   if (GetAddress >= (uint8_t*) MAP_LAST)
      return GetAddress[address & 0xffff];

   switch ((intptr_t) GetAddress)
   {
   case MAP_PPU:
      return S9xGetSA1(address & 0xffff);
   case MAP_LOROM_SRAM:
   case MAP_SA1RAM:
      return Memory.SRAM[address & 0xffff];
   case MAP_BWRAM:
      return SA1.BWRAM[(address & 0x7fff) - 0x6000];
   case MAP_BWRAM_BITMAP:
      address -= 0x600000;
      if (SA1.VirtualBitmapFormat == 2)
         return (Memory.SRAM [(address >> 2) & 0xffff] >> ((address & 3) << 1)) & 3;
      else
         return (Memory.SRAM [(address >> 1) & 0xffff] >> ((address & 1) << 2)) & 15;
   case MAP_BWRAM_BITMAP2:
      address = (address & 0xffff) - 0x6000;
      if (SA1.VirtualBitmapFormat == 2)
         return (SA1.BWRAM [(address >> 2) & 0xffff] >> ((address & 3) << 1)) & 3;
      else
         return (SA1.BWRAM [(address >> 1) & 0xffff] >> ((address & 1) << 2)) & 15;
   default:
      return OpenBus;
   }
}

uint16_t S9xSA1GetWord(uint32_t address)
{
   OpenBus = S9xSA1GetByte(address);
   return OpenBus | (S9xSA1GetByte(address + 1) << 8);
}

void S9xSA1SetByte(uint8_t byte, uint32_t address)
{
   uint8_t* SetAddress = SA1.WriteMap [(address >> MEMMAP_SHIFT) & MEMMAP_MASK];

   if (SetAddress >= (uint8_t*) MAP_LAST)
   {
      SetAddress[address & 0xffff] = byte;
      return;
   }

   switch ((intptr_t) SetAddress)
   {
   case MAP_PPU:
      S9xSetSA1(byte, address & 0xffff);
      return;
   case MAP_SA1RAM:
   case MAP_LOROM_SRAM:
      Memory.SRAM[address & 0xffff] = byte;
      return;
   case MAP_BWRAM:
      SA1.BWRAM[(address & 0x7fff) - 0x6000] = byte;
      return;
   case MAP_BWRAM_BITMAP:
      address -= 0x600000;
      if (SA1.VirtualBitmapFormat == 2)
      {
         uint8_t* ptr = &Memory.SRAM [(address >> 2) & 0xffff];
         *ptr &= ~(3 << ((address & 3) << 1));
         *ptr |= (byte & 3) << ((address & 3) << 1);
      }
      else
      {
         uint8_t* ptr = &Memory.SRAM [(address >> 1) & 0xffff];
         *ptr &= ~(15 << ((address & 1) << 2));
         *ptr |= (byte & 15) << ((address & 1) << 2);
      }
      break;
   case MAP_BWRAM_BITMAP2:
      address = (address & 0xffff) - 0x6000;
      if (SA1.VirtualBitmapFormat == 2)
      {
         uint8_t* ptr = &SA1.BWRAM[(address >> 2) & 0xffff];
         *ptr &= ~(3 << ((address & 3) << 1));
         *ptr |= (byte & 3) << ((address & 3) << 1);
      }
      else
      {
         uint8_t* ptr = &SA1.BWRAM [(address >> 1) & 0xffff];
         *ptr &= ~(15 << ((address & 1) << 2));
         *ptr |= (byte & 15) << ((address & 1) << 2);
      }
   }
}

void S9xSA1SetWord(uint16_t Word, uint32_t address)
{
   S9xSA1SetByte((uint8_t) Word, address);
   S9xSA1SetByte((uint8_t)(Word >> 8), address + 1);
}

void S9xSA1SetPCBase(uint32_t address)
{
   uint8_t* GetAddress = SA1.Map [(address >> MEMMAP_SHIFT) & MEMMAP_MASK];
   if (GetAddress >= (uint8_t*) MAP_LAST)
   {
      SA1.PCBase = GetAddress;
      SA1.PC = GetAddress + (address & 0xffff);
      return;
   }

   switch ((intptr_t) GetAddress)
   {
   case MAP_PPU:
      SA1.PCBase = Memory.FillRAM - 0x2000;
      break;
   case MAP_CPU:
      SA1.PCBase = Memory.FillRAM - 0x4000;
      break;
   case MAP_DSP:
      SA1.PCBase = Memory.FillRAM - 0x6000;
      break;
   case MAP_SA1RAM:
   case MAP_LOROM_SRAM:
      SA1.PCBase = Memory.SRAM;
      break;
   case MAP_BWRAM:
      SA1.PCBase = SA1.BWRAM - 0x6000;
      break;
   case MAP_HIROM_SRAM:
      SA1.PCBase = Memory.SRAM - 0x6000;
      break;
   default:
      SA1.PCBase = Memory.RAM;
      break;
   }

   SA1.PC = SA1.PCBase + (address & 0xffff);
}

void S9xSetSA1MemMap(uint32_t which1, uint8_t map)
{
   int32_t c;
   int32_t i;
   int32_t start = which1 * 0x100 + 0xc00;
   int32_t start2 = which1 * 0x200;
   uint8_t* block;

   if (which1 >= 2)
      start2 += 0x400;

   for (c = 0; c < 0x100; c += 16)
   {
      block = &Memory.ROM [(map & 7) * 0x100000 + (c << 12)];
      for (i = c; i < c + 16; i++)
         Memory.Map [start + i] = SA1.Map [start + i] = block;
   }

   for (c = 0; c < 0x200; c += 16)
   {
      /* Code from Snes9x 1.54.1 - This allows Super Mario World VLDC 9 hack to load.
         Conversion to int is needed here - map is promoted but which1 is not */
      int32_t offset = (((map & 0x80) ? map : which1) & 7) * 0x100000 + (c << 11) - 0x8000;
      block = &Memory.ROM [offset];
      for (i = c + 8; i < c + 16; i++)
         Memory.Map [start2 + i] = SA1.Map [start2 + i] = block;
   }
}

uint8_t S9xGetSA1(uint32_t address)
{
   switch (address)
   {
   case 0x2300:
      return (Memory.FillRAM[0x2209] & 0x5f) | (Memory.FillRAM[0x2300] & 0xa0);
   case 0x2301:
      return (Memory.FillRAM[0x2200] & 0x0f) | (Memory.FillRAM[0x2301] & 0xf0);
   case 0x2306:
      return (uint8_t) SA1.sum;
   case 0x2307:
      return (uint8_t) (SA1.sum >>  8);
   case 0x2308:
      return (uint8_t) (SA1.sum >> 16);
   case 0x2309:
      return (uint8_t) (SA1.sum >> 24);
   case 0x230a:
      return (uint8_t) (SA1.sum >> 32);
   case 0x230b:
      return SA1.overflow ? 0x80 : 0;
   case 0x230c:
      return Memory.FillRAM[0x230c];
   case 0x230d:
   {
      uint8_t byte = Memory.FillRAM[0x230d];

      if (Memory.FillRAM[0x2258] & 0x80)
         S9xSA1ReadVariableLengthData(true, false);
      return byte;
   }
   case 0x230e: /* version code register */
      return 0x01;
   default:
      break;
   }

   return Memory.FillRAM[address];
}

void S9xSetSA1(uint8_t byte, uint32_t address)
{
   if (address < 0x2200 || address > 0x22ff)
      return;

   switch (address)
   {
   case 0x2200:
      SA1.Waiting = (byte & 0x60) != 0;

      if (!(byte & 0x80) && (Memory.FillRAM[0x2200] & 0x20))
         S9xSA1Reset();
      if (byte & 0x80)
      {
         Memory.FillRAM[0x2301] |= 0x80;
         if (Memory.FillRAM[0x220a] & 0x80)
         {
            Memory.FillRAM[0x220b] &= ~0x80;
            SA1.Flags |= IRQ_PENDING_FLAG;
            SA1.IRQActive |= SNES_IRQ_SOURCE;
            SA1.Executing = !SA1.Waiting && SA1.S9xOpcodes;
         }
      }
      if (byte & 0x10)
      {
         Memory.FillRAM[0x2301] |= 0x10;
         if (Memory.FillRAM[0x220a] & 0x10)
            Memory.FillRAM[0x220b] &= ~0x10;
      }
      break;
   case 0x2201:
      if (((byte ^ Memory.FillRAM[0x2201]) & 0x80) && (Memory.FillRAM[0x2300] & byte & 0x80))
      {
         Memory.FillRAM[0x2202] &= ~0x80;
         S9xSetIRQ(SA1_IRQ_SOURCE);
      }
      if (((byte ^ Memory.FillRAM[0x2201]) & 0x20) && (Memory.FillRAM[0x2300] & byte & 0x20))
      {
         Memory.FillRAM[0x2202] &= ~0x20;
         S9xSetIRQ(SA1_DMA_IRQ_SOURCE);
      }
      break;
   case 0x2202:
      if (byte & 0x80)
      {
         Memory.FillRAM [0x2300] &= ~0x80;
         S9xClearIRQ(SA1_IRQ_SOURCE);
      }
      if (byte & 0x20)
      {
         Memory.FillRAM [0x2300] &= ~0x20;
         S9xClearIRQ(SA1_DMA_IRQ_SOURCE);
      }
      break;
   case 0x2209:
      if (byte & 0x80)
      {
         Memory.FillRAM[0x2300] |= 0x80;
         if (Memory.FillRAM[0x2201] & 0x80)
         {
            Memory.FillRAM[0x2202] &= ~0x80;
            S9xSetIRQ(SA1_IRQ_SOURCE);
         }
      }
      break;
   case 0x220a:
      if (((byte ^ Memory.FillRAM[0x220a]) & 0x80) && (Memory.FillRAM[0x2301] & byte & 0x80))
      {
         Memory.FillRAM[0x220b] &= ~0x80;
         SA1.Flags |= IRQ_PENDING_FLAG;
         SA1.IRQActive |= SNES_IRQ_SOURCE;
      }
      if (((byte ^ Memory.FillRAM[0x220a]) & 0x40) && (Memory.FillRAM[0x2301] & byte & 0x40))
      {
         Memory.FillRAM[0x220b] &= ~0x40;
         SA1.Flags |= IRQ_PENDING_FLAG;
         SA1.IRQActive |= TIMER_IRQ_SOURCE;
      }
      if (((byte ^ Memory.FillRAM[0x220a]) & 0x20) && (Memory.FillRAM[0x2301] & byte & 0x20))
      {
         Memory.FillRAM[0x220b] &= ~0x20;
         SA1.Flags |= IRQ_PENDING_FLAG;
         SA1.IRQActive |= DMA_IRQ_SOURCE;
      }
      if (((byte ^ Memory.FillRAM[0x220a]) & 0x10) && (Memory.FillRAM[0x2301] & byte & 0x10))
         Memory.FillRAM[0x220b] &= ~0x10;
      break;
   case 0x220b:
      if (byte & 0x80)
      {
         SA1.IRQActive &= ~SNES_IRQ_SOURCE;
         Memory.FillRAM [0x2301] &= ~0x80;
      }
      if (byte & 0x40)
      {
         SA1.IRQActive &= ~TIMER_IRQ_SOURCE;
         Memory.FillRAM [0x2301] &= ~0x40;
      }
      if (byte & 0x20)
      {
         SA1.IRQActive &= ~DMA_IRQ_SOURCE;
         Memory.FillRAM [0x2301] &= ~0x20;
      }
      if (byte & 0x10)
         Memory.FillRAM [0x2301] &= ~0x10;
      if (!SA1.IRQActive)
         SA1.Flags &= ~IRQ_PENDING_FLAG;
      break;
   case 0x2220:
   case 0x2221:
   case 0x2222:
   case 0x2223:
      S9xSetSA1MemMap(address - 0x2220, byte);
      break;
   case 0x2224:
      Memory.BWRAM = Memory.SRAM + (byte & 7) * 0x2000;
      break;
   case 0x2225:
      if (byte != Memory.FillRAM [address])
         S9xSA1SetBWRAMMemMap(byte);
      break;
   case 0x2231:
      if (byte & 0x80)
         SA1.in_char_dma = 0;
      break;
   case 0x2236: /* DMA destination start address (LH) */
      Memory.FillRAM[address] = byte;
      if ((Memory.FillRAM[0x2230] & 0xa4) == 0x80) /* Normal DMA to I-RAM */
         S9xSA1DMA(); /* Normal DMA to I-RAM */
      else if ((Memory.FillRAM[0x2230] & 0xb0) == 0xb0)
      {
         SA1.in_char_dma = 1;
         Memory.FillRAM[0x2300] |= 0x20;
         if (Memory.FillRAM[0x2201] & 0x20)
         {
            Memory.FillRAM[0x2202] &= ~0x20;
            S9xSetIRQ(SA1_DMA_IRQ_SOURCE);
         }
      }
      break;
   case 0x2237:
      Memory.FillRAM [address] = byte;
      if ((Memory.FillRAM [0x2230] & 0xa4) == 0x84)
         S9xSA1DMA(); /* Normal DMA to BW-RAM */
      break;
   case 0x223f:
      SA1.VirtualBitmapFormat = (byte & 0x80) ? 2 : 4;
      break;
   case 0x224f:
      Memory.FillRAM [address] = byte;
      if ((Memory.FillRAM [0x2230] & 0xb0) == 0xa0)
      {
         /* Char conversion 2 DMA enabled */
         /* memmove converted: Same malloc but constant non-overlapping addresses [Neb] */
         memcpy(&Memory.ROM [MAX_ROM_SIZE - 0x10000] + (SA1.in_char_dma << 4), &Memory.FillRAM [0x2240], 16);
         SA1.in_char_dma = (SA1.in_char_dma + 1) & 7;
         if ((SA1.in_char_dma & 3) == 0)
            S9xSA1CharConv2();
      }
      break;
   case 0x2250:
      if (byte & 2)
         SA1.sum = 0;
      SA1.arithmetic_op = byte & 3;
      break;
   case 0x2251:
      SA1.op1 = (SA1.op1 & 0xff00) | byte;
      break;
   case 0x2252:
      SA1.op1 = (SA1.op1 & 0x00ff) | (byte << 8);
      break;
   case 0x2253:
      SA1.op2 = (SA1.op2 & 0xff00) | byte;
      break;
   case 0x2254:
      SA1.op2 = (SA1.op2 & 0x00ff) | (byte << 8);
      switch (SA1.arithmetic_op)
      {
      case 0: /* multiply */
         SA1.sum = (int16_t) SA1.op1 * (int16_t) SA1.op2;
         SA1.op2 = 0;
         break;
      case 1: /* divide */
         if (SA1.op2 == 0)
            SA1.sum = 0;
         else
         {
            int16_t quotient  = (int16_t) SA1.op1 / (uint16_t) SA1.op2;
            uint16_t remainder = (int16_t) SA1.op1 % (uint16_t) SA1.op2;
            SA1.sum = (remainder << 16) | quotient;
         }
         SA1.op1 = 0;
         SA1.op2 = 0;
         break;
      default: /* cumulative sum */
         SA1.sum += (int16_t) SA1.op1 * (int16_t) SA1.op2;
         SA1.overflow = (SA1.sum >= (((uint64_t) 1) << 40));
         SA1.sum &= (((uint64_t) 1) << 40) - 1;
         SA1.op2 = 0;
         break;
      }
      break;
   case 0x2258: /* Variable bit-field length/auto inc/start. */
      Memory.FillRAM[0x2258] = byte;
      S9xSA1ReadVariableLengthData(true, false);
      return;
   case 0x2259:
   case 0x225a:
   case 0x225b: /* Variable bit-field start address */
      Memory.FillRAM[address] = byte;
      SA1.variable_bit_pos = 0;
      S9xSA1ReadVariableLengthData(false, true);
      return;
   default:
      break;
   }

   Memory.FillRAM[address] = byte;
}

static void S9xSA1CharConv2(void)
{
   uint32_t dest = Memory.FillRAM[0x2235] | (Memory.FillRAM[0x2236] << 8);
   uint32_t offset = (SA1.in_char_dma & 7) ? 0 : 1;
   int32_t depthX8 = (Memory.FillRAM[0x2231] & 3) == 0 ? 64 : (Memory.FillRAM[0x2231] & 3) == 1 ? 32 : 16;
   uint8_t* p = &Memory.FillRAM[0x3000] + (dest & 0x7ff) + offset * depthX8;
   uint8_t* q = &Memory.ROM[MAX_ROM_SIZE - 0x10000] + offset * 64;
   int l, b;

   switch(depthX8)
   {
      case 16:
         for (l = 0; l < 8; l++, q += 8)
         {
            for (b = 0; b < 8; b++)
            {
               uint8_t r = q[b];
               p[0] = (p[0] << 1) | ((r >> 0) & 1);
               p[1] = (p[1] << 1) | ((r >> 1) & 1);
            }
            p += 2;
         }
         break;
      case 32:
         for (l = 0; l < 8; l++, q += 8)
         {
            for (b = 0; b < 8; b++)
            {
               uint8_t r = q[b];
               p[0]  = (p[0]  << 1) | ((r >> 0) & 1);
               p[1]  = (p[1]  << 1) | ((r >> 1) & 1);
               p[16] = (p[16] << 1) | ((r >> 2) & 1);
               p[17] = (p[17] << 1) | ((r >> 3) & 1);
            }
            p += 2;
         }
         break;
      case 64:
         for (l = 0; l < 8; l++, q += 8)
         {
            for (b = 0; b < 8; b++)
            {
               uint8_t r = q[b];
               p[0]  = (p[0]  << 1) | ((r >> 0) & 1);
               p[1]  = (p[1]  << 1) | ((r >> 1) & 1);
               p[16] = (p[16] << 1) | ((r >> 2) & 1);
               p[17] = (p[17] << 1) | ((r >> 3) & 1);
               p[32] = (p[32] << 1) | ((r >> 4) & 1);
               p[33] = (p[33] << 1) | ((r >> 5) & 1);
               p[48] = (p[48] << 1) | ((r >> 6) & 1);
               p[49] = (p[49] << 1) | ((r >> 7) & 1);
            }
            p += 2;
         }
         break;
   }
}

static void S9xSA1DMA()
{
   uint32_t src = Memory.FillRAM[0x2232] | (Memory.FillRAM[0x2233] << 8) | (Memory.FillRAM[0x2234] << 16);
   uint32_t dst = Memory.FillRAM[0x2235] | (Memory.FillRAM[0x2236] << 8) | (Memory.FillRAM[0x2237] << 16);
   uint32_t len = Memory.FillRAM[0x2238] | (Memory.FillRAM[0x2239] << 8);
   uint8_t* s;
   uint8_t* d;

   switch (Memory.FillRAM [0x2230] & 3)
   {
   case 0: /* ROM */
      s = SA1.Map [(src >> MEMMAP_SHIFT) & MEMMAP_MASK];
      if (s >= (uint8_t*) MAP_LAST)
         s += (src & 0xffff);
      else
         s = Memory.ROM + (src & 0xffff);
      break;
   case 1: /* BW-RAM */
      src &= Memory.SRAMMask;
      len &= Memory.SRAMMask;
      s = Memory.SRAM + src;
      break;
   default:
      src &= 0x3ff;
      len &= 0x3ff;
      s = &Memory.FillRAM [0x3000] + src;
      break;
   }

   if (Memory.FillRAM [0x2230] & 4)
   {
      dst &= Memory.SRAMMask;
      len &= Memory.SRAMMask;
      d = Memory.SRAM + dst;
   }
   else
   {
      dst &= 0x3ff;
      len &= 0x3ff;
      d = &Memory.FillRAM [0x3000] + dst;
   }
   /* memmove required: Can overlap arbitrarily [Neb] */
   memmove(d, s, len);
   Memory.FillRAM [0x2301] |= 0x20;

   if (Memory.FillRAM [0x220a] & 0x20)
   {
      SA1.Flags |= IRQ_PENDING_FLAG;
      SA1.IRQActive |= DMA_IRQ_SOURCE;
   }
}

void S9xSA1ReadVariableLengthData(bool inc, bool no_shift)
{
   uint8_t s;
   uint32_t data;
   uint32_t addr = Memory.FillRAM[0x2259] | (Memory.FillRAM[0x225a] << 8) | (Memory.FillRAM[0x225b] << 16);
   uint8_t shift = Memory.FillRAM [0x2258] & 15;

   if (no_shift)
      shift = 0;
   else if (shift == 0)
      shift = 16;

   s = shift + SA1.variable_bit_pos;

   if (s >= 16)
   {
      addr += (s >> 4) << 1;
      s &= 15;
   }
   data = S9xSA1GetWord(addr) | (S9xSA1GetWord(addr + 2) << 16);

   data >>= s;
   Memory.FillRAM [0x230c] = (uint8_t) data;
   Memory.FillRAM [0x230d] = (uint8_t)(data >> 8);
   if (inc)
   {
      SA1.variable_bit_pos = (SA1.variable_bit_pos + shift) & 15;
      Memory.FillRAM [0x2259] = (uint8_t) addr;
      Memory.FillRAM [0x225a] = (uint8_t)(addr >> 8);
      Memory.FillRAM [0x225b] = (uint8_t)(addr >> 16);
   }
}