path: root/src/apu.c

/*
 * Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
 *
 * (c) Copyright 1996 - 2001 Gary Henderson (gary.henderson@ntlworld.com) and
 *                           Jerremy Koot (jkoot@snes9x.com)
 *
 * Super FX C emulator code
 * (c) Copyright 1997 - 1999 Ivar (ivar@snes9x.com) and
 *                           Gary Henderson.
 * Super FX assembler emulator code (c) Copyright 1998 zsKnight and _Demo_.
 *
 * DSP1 emulator code (c) Copyright 1998 Ivar, _Demo_ and Gary Henderson.
 * C4 asm and some C emulation code (c) Copyright 2000 zsKnight and _Demo_.
 * C4 C code (c) Copyright 2001 Gary Henderson (gary.henderson@ntlworld.com).
 *
 * DOS port code contains the works of other authors. See headers in
 * individual files.
 *
 * Snes9x homepage: http://www.snes9x.com
 *
 * Permission to use, copy, modify and distribute Snes9x in both binary and
 * source form, for non-commercial purposes, is hereby granted without fee,
 * providing that this license information and copyright notice appear with
 * all copies and any derived work.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty. In no event shall the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Snes9x is freeware for PERSONAL USE only. Commercial users should
 * seek permission of the copyright holders first. Commercial use includes
 * charging money for Snes9x or software derived from Snes9x.
 *
 * The copyright holders request that bug fixes and improvements to the code
 * should be forwarded to them so everyone can benefit from the modifications
 * in future versions.
 *
 * Super NES and Super Nintendo Entertainment System are trademarks of
 * Nintendo Co., Limited and its subsidiary companies.
 */

#include "snes9x.h"
#include "spc700.h"
#include "apu.h"
#include "soundux.h"
#include "cpuexec.h"

#undef ABS
#define ABS(a) ((a) < 0 ? -(a) : (a))
#define ENVX_SHIFT 24


unsigned long AttackRate [16] =
{
   4100, 2600, 1500, 1000, 640, 380, 260, 160,
   96, 64, 40, 24, 16, 10, 6, 1
};

unsigned long DecayRate [8] =
{
   1200, 740, 440, 290, 180, 110, 74, 37
};

unsigned long SustainRate [32] =
{
   /*~0*/0xFFFFFFFF, 38000, 28000, 24000, 19000, 14000, 12000, 9400,
   7100, 5900, 4700, 3500, 2900, 2400, 1800, 1500,
   1200, 880, 740, 590, 440, 370, 290, 220,
   180, 150, 110, 92, 74, 55, 37, 18
};

unsigned long IncreaseRate [32] =
{
   /*~0*/0xFFFFFFFF, 4100, 3100, 2600, 2000, 1500, 1300, 1000,
   770, 640, 510, 380, 320, 260, 190, 160,
   130, 96, 80, 64, 48, 40, 32, 24,
   20, 16, 12, 10, 8, 6, 4, 2
};

unsigned long DecreaseRateExp [32] =
{
   /*~0*/0xFFFFFFFF, 38000, 28000, 24000, 19000, 14000, 12000, 9400,
   7100, 5900, 4700, 3500, 2900, 2400, 1800, 1500,
   1200, 880, 740, 590, 440, 370, 290, 220,
   180, 150, 110, 92, 74, 55, 37, 18
};

// precalculated env rates for S9xSetEnvRate
unsigned long AttackERate     [16][10];
unsigned long DecayERate       [8][10];
unsigned long SustainERate    [32][10];
unsigned long IncreaseERate   [32][10];
unsigned long DecreaseERateExp[32][10];
unsigned long KeyOffERate[10];


static inline void S9xSetEnvelopeRate(int channel, unsigned long rate, int direction, int target, unsigned int mode)
{
   S9xSetEnvRate(&SoundData.channels [channel], rate, direction, target, mode);
}

static inline void S9xSetSoundADSR(int channel, int attack_ind, int decay_ind,
                                   int sustain_ind, int sustain_level, int release_rate)
{
   int attack_rate = AttackRate [attack_ind];
   int decay_rate = DecayRate [decay_ind];
   int sustain_rate = SustainRate [sustain_ind];

   // Hack for ROMs that use a very short attack rate, key on a
   // channel, then switch to decay mode. e.g. Final Fantasy II.
   if (attack_rate == 1)
      attack_rate = 0;

   SoundData.channels[channel].env_ind_attack = attack_ind;
   SoundData.channels[channel].env_ind_decay = decay_ind;
   SoundData.channels[channel].env_ind_sustain = sustain_ind;

   SoundData.channels[channel].attack_rate = attack_rate;
   SoundData.channels[channel].decay_rate = decay_rate;
   SoundData.channels[channel].sustain_rate = sustain_rate;
   SoundData.channels[channel].release_rate = release_rate;
   SoundData.channels[channel].sustain_level = sustain_level + 1;

   switch (SoundData.channels[channel].state)
   {
   case SOUND_ATTACK:
      S9xSetEnvelopeRate(channel, attack_rate, 1, 127, 0);
      break;

   case SOUND_DECAY:
      S9xSetEnvelopeRate(channel, decay_rate, -1,
                         (MAX_ENVELOPE_HEIGHT * (sustain_level + 1)) >> 3, 1 << 28);
      break;
   case SOUND_SUSTAIN:
      S9xSetEnvelopeRate(channel, sustain_rate, -1, 0, 2 << 28);
      break;
   }
}

static inline void S9xSetSoundVolume(int channel, short volume_left, short volume_right)
{
   Channel* ch = &SoundData.channels[channel];
   if (!so.stereo)
      volume_left = (ABS(volume_right) + ABS(volume_left)) / 2;

   ch->volume_left = volume_left;
   ch->volume_right = volume_right;
   ch-> left_vol_level = (ch->envx * volume_left) / 128;
   ch->right_vol_level = (ch->envx * volume_right) / 128;
}

static inline void S9xSetMasterVolume(short volume_left, short volume_right)
{
   if (Settings.DisableMasterVolume)
   {
      SoundData.master_volume_left = 127;
      SoundData.master_volume_right = 127;
      SoundData.master_volume [0] = SoundData.master_volume [1] = 127;
   }
   else
   {
      if (!so.stereo)
         volume_left = (ABS(volume_right) + ABS(volume_left)) / 2;
      SoundData.master_volume_left = volume_left;
      SoundData.master_volume_right = volume_right;
      SoundData.master_volume [0] = volume_left;
      SoundData.master_volume [1] = volume_right;
   }
}

static inline void S9xSetEchoVolume(short volume_left, short volume_right)
{
   if (!so.stereo)
      volume_left = (ABS(volume_right) + ABS(volume_left)) / 2;
   SoundData.echo_volume_left = volume_left;
   SoundData.echo_volume_right = volume_right;
   SoundData.echo_volume [0] = volume_left;
   SoundData.echo_volume [1] = volume_right;
}

static inline void S9xSetEchoWriteEnable(uint8 byte)
{
   SoundData.echo_write_enabled = byte;
   S9xSetEchoDelay(APU.DSP [APU_EDL] & 15);
}

static inline void S9xSetFrequencyModulationEnable(uint8 byte)
{
   SoundData.pitch_mod = byte & (0xFE);//~1;
}

static inline int S9xGetEnvelopeHeight(int channel)
{
   if ((Settings.SoundEnvelopeHeightReading ||
         SNESGameFixes.SoundEnvelopeHeightReading2) &&
         SoundData.channels[channel].state != SOUND_SILENT &&
         SoundData.channels[channel].state != SOUND_GAIN)
      return (SoundData.channels[channel].envx);

   //siren fix from XPP
   if (SNESGameFixes.SoundEnvelopeHeightReading2 &&
         SoundData.channels[channel].state != SOUND_SILENT)
      return (SoundData.channels[channel].envx);

   return (0);
}

static inline void S9xSetSoundHertz(int channel, int hertz)
{
   SoundData.channels[channel].hertz = hertz;
   S9xSetSoundFrequency(channel, hertz);
}

static inline void S9xSetSoundType(int channel, int type_of_sound)
{
   SoundData.channels[channel].type = type_of_sound;
}

static inline bool8 S9xSetSoundMode(int channel, int mode)
{
   Channel* ch = &SoundData.channels[channel];

   switch (mode)
   {
   case MODE_RELEASE:
      if (ch->mode != MODE_NONE)
      {
         ch->mode = MODE_RELEASE;
         return (TRUE);
      }
      break;

   case MODE_DECREASE_LINEAR:
   case MODE_DECREASE_EXPONENTIAL:
   case MODE_GAIN:
      if (ch->mode != MODE_RELEASE)
      {
         ch->mode = mode;
         if (ch->state != SOUND_SILENT)
            ch->state = mode;

         return (TRUE);
      }
      break;

   case MODE_INCREASE_LINEAR:
   case MODE_INCREASE_BENT_LINE:
      if (ch->mode != MODE_RELEASE)
      {
         ch->mode = mode;
         if (ch->state != SOUND_SILENT)
            ch->state = mode;




         return (TRUE);
      }
      break;

   case MODE_ADSR:
      if (ch->mode == MODE_NONE || ch->mode == MODE_ADSR)
      {
         ch->mode = mode;
         return (TRUE);
      }
   }

   return (FALSE);
}

static inline void S9xPlaySample(int channel)
{
   Channel* ch = &SoundData.channels[channel];

   ch->state = SOUND_SILENT;
   ch->mode = MODE_NONE;
   ch->envx = 0;
   ch->envxx = 0;

   ch->g_index = 0;
   ch->gaussian[0] = ch->gaussian[1] = ch->gaussian[2] = ch->gaussian[3] = 0;

   S9xFixEnvelope(channel,
                  APU.DSP [APU_GAIN  + (channel << 4)],
                  APU.DSP [APU_ADSR1 + (channel << 4)],
                  APU.DSP [APU_ADSR2 + (channel << 4)]);

   ch->sample_number = APU.DSP [APU_SRCN + channel * 0x10];
   if (APU.DSP [APU_NON] & (1 << channel))
      ch->type = SOUND_NOISE;
   else
      ch->type = SOUND_SAMPLE;

   S9xSetSoundFrequency(channel, ch->hertz);
   ch->loop = FALSE;
   ch->needs_decode = TRUE;
   ch->last_block = FALSE;
   ch->previous [0] = ch->previous[1] = 0;
   ch->block_pointer = *S9xGetSampleAddress(ch->sample_number);
   ch->sample_pointer = 0;
   ch->env_error = 0;
   ch->next_sample = 0;
   ch->interpolate = 0;
   ch->last_valid_header = 0;
   switch (ch->mode)
   {
   case MODE_ADSR:
      if (ch->attack_rate == 0)
      {
         if (ch->decay_rate == 0 || ch->sustain_level == 8)
         {
            ch->state = SOUND_SUSTAIN;
            ch->envx = (MAX_ENVELOPE_HEIGHT * ch->sustain_level) >> 3;
            S9xSetEnvRate(ch, ch->sustain_rate, -1, 0, 2 << 28);
         }
         else
         {
            ch->state = SOUND_DECAY;
            ch->envx = MAX_ENVELOPE_HEIGHT;
            S9xSetEnvRate(ch, ch->decay_rate, -1,
                          (MAX_ENVELOPE_HEIGHT * ch->sustain_level) >> 3, 1 << 28);
         }
         ch-> left_vol_level = (ch->envx * ch->volume_left) / 128;
         ch->right_vol_level = (ch->envx * ch->volume_right) / 128;
      }
      else
      {
         ch->state = SOUND_ATTACK;
         ch->envx = 0;
         ch->left_vol_level = 0;
         ch->right_vol_level = 0;
         S9xSetEnvRate(ch, ch->attack_rate, 1, MAX_ENVELOPE_HEIGHT, 0);
      }
      ch->envxx = ch->envx << ENVX_SHIFT;
      break;

   case MODE_GAIN:
      ch->state = SOUND_GAIN;
      break;

   case MODE_INCREASE_LINEAR:
      ch->state = SOUND_INCREASE_LINEAR;
      break;

   case MODE_INCREASE_BENT_LINE:
      ch->state = SOUND_INCREASE_BENT_LINE;
      break;

   case MODE_DECREASE_LINEAR:
      ch->state = SOUND_DECREASE_LINEAR;
      break;

   case MODE_DECREASE_EXPONENTIAL:
      ch->state = SOUND_DECREASE_EXPONENTIAL;
      break;

   default:
      break;
   }

   S9xFixEnvelope(channel,
                  APU.DSP [APU_GAIN  + (channel << 4)],
                  APU.DSP [APU_ADSR1 + (channel << 4)],
                  APU.DSP [APU_ADSR2 + (channel << 4)]);
}

uint32 Spc700JumpTab_15;

bool8 S9xInitAPU()
{
   // notaz
   memset(&IAPU, 0, sizeof(IAPU));
   IAPU.ExtraRAM = APU.ExtraRAM;
   IAPU.asmJumpTab = &Spc700JumpTab_15;  // Normal case: ONE_APU_CYCLE = 15

   IAPU.RAM = (uint8*) malloc(0x10000);
   IAPU.ShadowRAM = NULL;//(uint8 *) malloc (0x10000);
   IAPU.CachedSamples = NULL;//(uint8 *) malloc (0x40000);

   if (!IAPU.RAM /*|| !IAPU.ShadowRAM || !IAPU.CachedSamples*/)
   {
      S9xDeinitAPU();
      return (FALSE);
   }

   return (TRUE);
}

void S9xDeinitAPU()
{
   if (IAPU.RAM)
   {
      free((char*) IAPU.RAM);
      IAPU.RAM = NULL;
   }
   if (IAPU.ShadowRAM)
   {
      free((char*) IAPU.ShadowRAM);
      IAPU.ShadowRAM = NULL;
   }
   if (IAPU.CachedSamples)
   {
      free((char*) IAPU.CachedSamples);
      IAPU.CachedSamples = NULL;
   }
}

EXTERN_C uint8 APUROM [64];

void S9xResetAPU()
{
   int i, j;
   //    Settings.APUEnabled = Settings.NextAPUEnabled;

   memset(IAPU.RAM, 0, 0x100);
   memset(IAPU.RAM + 0x20, 0xFF, 0x20);
   memset(IAPU.RAM + 0x60, 0xFF, 0x20);
   memset(IAPU.RAM + 0xA0, 0xFF, 0x20);
   memset(IAPU.RAM + 0xE0, 0xFF, 0x20);


   for (i = 1; i < 256; i++)
      memcpy(IAPU.RAM + (i << 8), IAPU.RAM, 0x100);
   //memset (IAPU.CachedSamples, 0, 0x40000);
   memset(APU.OutPorts, 0, 4);
   IAPU.DirectPage = IAPU.RAM;
   memmove(&IAPU.RAM [0xffc0], APUROM, sizeof(APUROM));
   memmove(APU.ExtraRAM, APUROM, sizeof(APUROM));
   IAPU.PC = IAPU.RAM + IAPU.RAM [0xfffe] + (IAPU.RAM [0xffff] << 8);
   CPU.APU_Cycles = 0;
   IAPU.YA.W = 0;
   IAPU.X = 0;
   IAPU.S = 0xff;
   IAPU.P = 0;
   S9xAPUUnpackStatus();
   CPU.APU_APUExecuting = Settings.APUEnabled;
#ifdef SPC700_SHUTDOWN
   IAPU.WaitAddress1 = NULL;
   IAPU.WaitAddress2 = NULL;
   IAPU.WaitCounter = 0;
#endif
   APU.ShowROM = TRUE;
   IAPU.RAM [0xf1] = 0x80;

   for (i = 0; i < 3; i++)
   {
      APU.TimerEnabled [i] = FALSE;
      APU.TimerValueWritten [i] = 0;
      APU.TimerTarget [i] = 0;
      APU.Timer [i] = 0;
   }
   for (j = 0; j < 0x80; j++)
      APU.DSP [j] = 0;

   IAPU.TwoCycles = IAPU.OneCycle * 2;

   for (i = 0; i < 256; i++)
      S9xAPUCycles [i] = S9xAPUCycleLengths [i] * IAPU.OneCycle;

   APU.DSP [APU_ENDX] = 0;
   APU.DSP [APU_KOFF] = 0;
   APU.DSP [APU_KON] = 0;
   APU.DSP [APU_FLG] = APU_MUTE | APU_ECHO_DISABLED;
   APU.KeyedChannels = 0;

   S9xResetSound(TRUE);
   S9xSetEchoEnable(0);
}

extern int framecpto;
void S9xSetAPUDSP(uint8 byte)
{
   uint8 reg = IAPU.RAM [0xf2];
   static uint8 KeyOn;
   static uint8 KeyOnPrev;
   int i;

   /*    char str[64];
       if (byte!=0)
       {
         sprintf(str,"fr : %d\nwrite dsp %d\ncpu cycle=%d pc=%04X",framecpto,byte,CPU.Cycles,CPU.PC-CPU.PCBase);
         S9xMessage(0,0,str);
         gp32_pause();
      }*/

   //extern uint8 spc_dump_dsp[0x100];

   //spc_dump_dsp[reg] = byte;

   switch (reg)
   {
   case APU_FLG:
      if (byte & APU_SOFT_RESET)
      {
         APU.DSP [reg] = APU_MUTE | APU_ECHO_DISABLED | (byte & 0x1f);
         APU.DSP [APU_ENDX] = 0;
         APU.DSP [APU_KOFF] = 0;
         APU.DSP [APU_KON] = 0;
         S9xSetEchoWriteEnable(FALSE);
         // Kill sound
         S9xResetSound(FALSE);
      }
      else
      {
         S9xSetEchoWriteEnable(!(byte & APU_ECHO_DISABLED));
         if (byte & APU_MUTE)
            S9xSetSoundMute(TRUE);
         else
            S9xSetSoundMute(FALSE);

         SoundData.noise_hertz = NoiseFreq [byte & 0x1f];
         for (i = 0; i < 8; i++)
         {
            if (SoundData.channels [i].type == SOUND_NOISE)
               S9xSetSoundFrequency(i, SoundData.noise_hertz);
         }
      }
      break;
   case APU_NON:
      if (byte != APU.DSP [APU_NON])
      {
         int c;
         uint8 mask = 1;
         for (c = 0; c < 8; c++, mask <<= 1)
         {
            int type;
            if (byte & mask)
               type = SOUND_NOISE;
            else
               type = SOUND_SAMPLE;
            S9xSetSoundType(c, type);
         }
      }
      break;
   case APU_MVOL_LEFT:
      if (byte != APU.DSP [APU_MVOL_LEFT])
      {
         S9xSetMasterVolume((signed char) byte,
                            (signed char) APU.DSP [APU_MVOL_RIGHT]);
      }
      break;
   case APU_MVOL_RIGHT:
      if (byte != APU.DSP [APU_MVOL_RIGHT])
      {
         S9xSetMasterVolume((signed char) APU.DSP [APU_MVOL_LEFT],
                            (signed char) byte);
      }
      break;
   case APU_EVOL_LEFT:
      if (byte != APU.DSP [APU_EVOL_LEFT])
      {
         S9xSetEchoVolume((signed char) byte,
                          (signed char) APU.DSP [APU_EVOL_RIGHT]);
      }
      break;
   case APU_EVOL_RIGHT:
      if (byte != APU.DSP [APU_EVOL_RIGHT])
      {
         S9xSetEchoVolume((signed char) APU.DSP [APU_EVOL_LEFT],
                          (signed char) byte);
      }
      break;
   case APU_ENDX:
      byte = 0;
      break;

   case APU_KOFF:
      //    if (byte)
   {
      int c;
      uint8 mask = 1;
      for (c = 0; c < 8; c++, mask <<= 1)
      {
         if ((byte & mask) != 0)
         {
            if (APU.KeyedChannels & mask)
            {
               {
                  KeyOnPrev &= ~mask;
                  APU.KeyedChannels &= ~mask;
                  APU.DSP [APU_KON] &= ~mask;
                  //APU.DSP [APU_KOFF] |= mask;
                  S9xSetSoundKeyOff(c);
               }
            }
         }
         else if ((KeyOnPrev & mask) != 0)
         {
            KeyOnPrev &= ~mask;
            APU.KeyedChannels |= mask;
            //APU.DSP [APU_KON] |= mask;
            APU.DSP [APU_KOFF] &= ~mask;
            APU.DSP [APU_ENDX] &= ~mask;
            S9xPlaySample(c);
         }
      }
   }
      //KeyOnPrev=0;
   APU.DSP [APU_KOFF] = byte;
   return;
   case APU_KON:

      if (byte)
      {
         int c;
         uint8 mask = 1;
         for (c = 0; c < 8; c++, mask <<= 1)
         {
            if ((byte & mask) != 0)
            {
               // Pac-In-Time requires that channels can be key-on
               // regardeless of their current state.
               if ((APU.DSP [APU_KOFF] & mask) == 0)
               {
                  KeyOnPrev &= ~mask;
                  APU.KeyedChannels |= mask;
                  //APU.DSP [APU_KON] |= mask;
                  //APU.DSP [APU_KOFF] &= ~mask;
                  APU.DSP [APU_ENDX] &= ~mask;
                  S9xPlaySample(c);
               }
               else KeyOn |= mask;
            }
         }
      }
      //spc_is_dumping_temp = byte;
      return;

   case APU_VOL_LEFT + 0x00:
   case APU_VOL_LEFT + 0x10:
   case APU_VOL_LEFT + 0x20:
   case APU_VOL_LEFT + 0x30:
   case APU_VOL_LEFT + 0x40:
   case APU_VOL_LEFT + 0x50:
   case APU_VOL_LEFT + 0x60:
   case APU_VOL_LEFT + 0x70:
      // At Shin Megami Tensei suggestion 6/11/00
      // if (byte != APU.DSP [reg])
   {
      S9xSetSoundVolume(reg >> 4, (signed char) byte,
                        (signed char) APU.DSP [reg + 1]);
   }
   break;
   case APU_VOL_RIGHT + 0x00:
   case APU_VOL_RIGHT + 0x10:
   case APU_VOL_RIGHT + 0x20:
   case APU_VOL_RIGHT + 0x30:
   case APU_VOL_RIGHT + 0x40:
   case APU_VOL_RIGHT + 0x50:
   case APU_VOL_RIGHT + 0x60:
   case APU_VOL_RIGHT + 0x70:
      // At Shin Megami Tensei suggestion 6/11/00
      // if (byte != APU.DSP [reg])
   {
      S9xSetSoundVolume(reg >> 4, (signed char) APU.DSP [reg - 1],
                        (signed char) byte);
   }
   break;

   case APU_P_LOW + 0x00:
   case APU_P_LOW + 0x10:
   case APU_P_LOW + 0x20:
   case APU_P_LOW + 0x30:
   case APU_P_LOW + 0x40:
   case APU_P_LOW + 0x50:
   case APU_P_LOW + 0x60:
   case APU_P_LOW + 0x70:
      S9xSetSoundHertz(reg >> 4, (((byte + (APU.DSP [reg + 1] << 8)) & FREQUENCY_MASK) * 32000) >> 12);
      break;

   case APU_P_HIGH + 0x00:
   case APU_P_HIGH + 0x10:
   case APU_P_HIGH + 0x20:
   case APU_P_HIGH + 0x30:
   case APU_P_HIGH + 0x40:
   case APU_P_HIGH + 0x50:
   case APU_P_HIGH + 0x60:
   case APU_P_HIGH + 0x70:
      S9xSetSoundHertz(reg >> 4,
                       (((byte << 8) + APU.DSP [reg - 1]) & FREQUENCY_MASK) * 8);
      break;

   case APU_SRCN + 0x00:
   case APU_SRCN + 0x10:
   case APU_SRCN + 0x20:
   case APU_SRCN + 0x30:
   case APU_SRCN + 0x40:
   case APU_SRCN + 0x50:
   case APU_SRCN + 0x60:
   case APU_SRCN + 0x70:
      if (byte != APU.DSP [reg])
      {
         //S9xSetSoundSample (reg >> 4, byte); // notaz: seems to be unused?
      }
      break;

   case APU_ADSR1 + 0x00:
   case APU_ADSR1 + 0x10:
   case APU_ADSR1 + 0x20:
   case APU_ADSR1 + 0x30:
   case APU_ADSR1 + 0x40:
   case APU_ADSR1 + 0x50:
   case APU_ADSR1 + 0x60:
   case APU_ADSR1 + 0x70:
      if (byte != APU.DSP [reg])
      {
         {
            S9xFixEnvelope(reg >> 4, APU.DSP [reg + 2], byte,
                           APU.DSP [reg + 1]);
         }
      }
      break;

   case APU_ADSR2 + 0x00:
   case APU_ADSR2 + 0x10:
   case APU_ADSR2 + 0x20:
   case APU_ADSR2 + 0x30:
   case APU_ADSR2 + 0x40:
   case APU_ADSR2 + 0x50:
   case APU_ADSR2 + 0x60:
   case APU_ADSR2 + 0x70:
      if (byte != APU.DSP [reg])
      {
         {
            S9xFixEnvelope(reg >> 4, APU.DSP [reg + 1], APU.DSP [reg - 1],
                           byte);
         }
      }
      break;

   case APU_GAIN + 0x00:
   case APU_GAIN + 0x10:
   case APU_GAIN + 0x20:
   case APU_GAIN + 0x30:
   case APU_GAIN + 0x40:
   case APU_GAIN + 0x50:
   case APU_GAIN + 0x60:
   case APU_GAIN + 0x70:
      if (byte != APU.DSP [reg])
      {
         {
            S9xFixEnvelope(reg >> 4, byte, APU.DSP [reg - 2],
                           APU.DSP [reg - 1]);
         }
      }
      break;

   case APU_ENVX + 0x00:
   case APU_ENVX + 0x10:
   case APU_ENVX + 0x20:
   case APU_ENVX + 0x30:
   case APU_ENVX + 0x40:
   case APU_ENVX + 0x50:
   case APU_ENVX + 0x60:
   case APU_ENVX + 0x70:
      break;

   case APU_OUTX + 0x00:
   case APU_OUTX + 0x10:
   case APU_OUTX + 0x20:
   case APU_OUTX + 0x30:
   case APU_OUTX + 0x40:
   case APU_OUTX + 0x50:
   case APU_OUTX + 0x60:
   case APU_OUTX + 0x70:
      break;

   case APU_DIR:
      break;

   case APU_PMON:
      if (byte != APU.DSP [APU_PMON])
         S9xSetFrequencyModulationEnable(byte);
      break;

   case APU_EON:
      if (byte != APU.DSP [APU_EON])
         S9xSetEchoEnable(byte);
      break;

   case APU_EFB:
      S9xSetEchoFeedback((signed char) byte);
      break;

   case APU_ESA:
      break;

   case APU_EDL:
      S9xSetEchoDelay(byte & 0xf);
      break;

   case APU_C0:
   case APU_C1:
   case APU_C2:
   case APU_C3:
   case APU_C4:
   case APU_C5:
   case APU_C6:
   case APU_C7:
      S9xSetFilterCoefficient(reg >> 4, (signed char) byte);
      break;
   default:
      // XXX
      //printf ("Write %02x to unknown APU register %02x\n", byte, reg);
      break;
   }

   KeyOnPrev |= KeyOn;
   KeyOn = 0;

   if (reg < 0x80)
      APU.DSP [reg] = byte;
}

void S9xFixEnvelope(int channel, uint8 gain, uint8 adsr1, uint8 adsr2)
{
   if (adsr1 & 0x80)
   {
      // ADSR mode

      // XXX: can DSP be switched to ADSR mode directly from GAIN/INCREASE/
      // DECREASE mode? And if so, what stage of the sequence does it start
      // at?
      if (S9xSetSoundMode(channel, MODE_ADSR))
         S9xSetSoundADSR(channel, adsr1 & 0xf, (adsr1 >> 4) & 7, adsr2 & 0x1f, (adsr2 >> 5) & 7, 8);
   }
   else
   {
      // Gain mode
      if ((gain & 0x80) == 0)
      {
         if (S9xSetSoundMode(channel, MODE_GAIN))
         {
            S9xSetEnvelopeRate(channel, 0, 0, gain & 0x7f, 0);
            S9xSetEnvelopeHeight(channel, gain & 0x7f);
         }
      }
      else
      {

         if (gain & 0x40)
         {
            // Increase mode
            if (S9xSetSoundMode(channel, (gain & 0x20) ?
                                MODE_INCREASE_BENT_LINE :
                                MODE_INCREASE_LINEAR))
               S9xSetEnvelopeRate(channel, IncreaseRate [gain & 0x1f], 1, 127, (3 << 28) | gain);
         }
         else
         {
            if (gain & 0x20)
            {
               if (S9xSetSoundMode(channel, MODE_DECREASE_EXPONENTIAL))
                  S9xSetEnvelopeRate(channel, DecreaseRateExp [gain & 0x1f] / 2, -1, 0, (4 << 28) | gain);
            }
            else
            {
               if (S9xSetSoundMode(channel, MODE_DECREASE_LINEAR))
                  S9xSetEnvelopeRate(channel, IncreaseRate [gain & 0x1f], -1, 0, (3 << 28) | gain);
            }
         }
      }
   }
}

void S9xSetAPUControl(uint8 byte)
{
   //if (byte & 0x40)
   //printf ("*** Special SPC700 timing enabled\n");
   if ((byte & 1) != 0 && !APU.TimerEnabled [0])
   {
      APU.Timer [0] = 0;
      IAPU.RAM [0xfd] = 0;
      if ((APU.TimerTarget [0] = IAPU.RAM [0xfa]) == 0)
         APU.TimerTarget [0] = 0x100;
   }
   if ((byte & 2) != 0 && !APU.TimerEnabled [1])
   {
      APU.Timer [1] = 0;
      IAPU.RAM [0xfe] = 0;
      if ((APU.TimerTarget [1] = IAPU.RAM [0xfb]) == 0)
         APU.TimerTarget [1] = 0x100;
   }
   if ((byte & 4) != 0 && !APU.TimerEnabled [2])
   {
      APU.Timer [2] = 0;
      IAPU.RAM [0xff] = 0;
      if ((APU.TimerTarget [2] = IAPU.RAM [0xfc]) == 0)
         APU.TimerTarget [2] = 0x100;
   }
   APU.TimerEnabled [0] = byte & 1;
   APU.TimerEnabled [1] = (byte & 2) >> 1;
   APU.TimerEnabled [2] = (byte & 4) >> 2;

   if (byte & 0x10)
      IAPU.RAM [0xF4] = IAPU.RAM [0xF5] = 0;

   if (byte & 0x20)
      IAPU.RAM [0xF6] = IAPU.RAM [0xF7] = 0;

   if (byte & 0x80)
   {
      if (!APU.ShowROM)
      {
         memmove(&IAPU.RAM [0xffc0], APUROM, sizeof(APUROM));
         APU.ShowROM = TRUE;
      }
   }
   else
   {
      if (APU.ShowROM)
      {
         APU.ShowROM = FALSE;
         memmove(&IAPU.RAM [0xffc0], APU.ExtraRAM, sizeof(APUROM));
      }
   }
   IAPU.RAM [0xf1] = byte;
}

void S9xSetAPUTimer(uint16 Address, uint8 byte)
{
   IAPU.RAM [Address] = byte;

   switch (Address)
   {
   case 0xfa:
      if ((APU.TimerTarget [0] = IAPU.RAM [0xfa]) == 0)
         APU.TimerTarget [0] = 0x100;
      APU.TimerValueWritten [0] = TRUE;
      break;
   case 0xfb:
      if ((APU.TimerTarget [1] = IAPU.RAM [0xfb]) == 0)
         APU.TimerTarget [1] = 0x100;
      APU.TimerValueWritten [1] = TRUE;
      break;
   case 0xfc:
      if ((APU.TimerTarget [2] = IAPU.RAM [0xfc]) == 0)
         APU.TimerTarget [2] = 0x100;
      APU.TimerValueWritten [2] = TRUE;
      break;
   }
}

uint8 S9xGetAPUDSP()
{
   uint8 reg = IAPU.RAM [0xf2] & 0x7f;
   uint8 byte = APU.DSP [reg];

   switch (reg)
   {
   case APU_KON:
      break;
   case APU_KOFF:
      break;
   case APU_OUTX + 0x00:
   case APU_OUTX + 0x10:
   case APU_OUTX + 0x20:
   case APU_OUTX + 0x30:
   case APU_OUTX + 0x40:
   case APU_OUTX + 0x50:
   case APU_OUTX + 0x60:
   case APU_OUTX + 0x70:
      if (SoundData.channels [reg >> 4].state == SOUND_SILENT)
         return (0);
      return ((SoundData.channels [reg >> 4].sample >> 8) |
              (SoundData.channels [reg >> 4].sample & 0xff));

   case APU_ENVX + 0x00:
   case APU_ENVX + 0x10:
   case APU_ENVX + 0x20:
   case APU_ENVX + 0x30:
   case APU_ENVX + 0x40:
   case APU_ENVX + 0x50:
   case APU_ENVX + 0x60:
   case APU_ENVX + 0x70:
      return 0;
   //    return ((uint8) S9xGetEnvelopeHeight (reg >> 4));

   case APU_ENDX:
      // To fix speech in Magical Drop 2 6/11/00
      // APU.DSP [APU_ENDX] = 0;
      break;
   default:
      break;
   }
   return (byte);
}