#include "nes_dmc.h"
#include "nes_apu.h"
#include <cstdlib>

namespace xgm
{
  const UINT32 NES_DMC::wavlen_table[2][16] = {
  { // NTSC
    4, 8, 16, 32, 64, 96, 128, 160, 202, 254, 380, 508, 762, 1016, 2034, 4068
  },
  { // PAL
    4, 8, 14, 30, 60, 88, 118, 148, 188, 236, 354, 472, 708,  944, 1890, 3778
  }};

  const UINT32 NES_DMC::freq_table[2][16] = {
  { // NTSC
    428, 380, 340, 320, 286, 254, 226, 214, 190, 160, 142, 128, 106, 84, 72, 54
  },
  { // PAL
    398, 354, 316, 298, 276, 236, 210, 198, 176, 148, 132, 118,  98, 78, 66, 50
  }};

  const UINT32 BITREVERSE[256] = {
    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
    0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
    0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
    0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, 0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
    0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
    0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA, 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
    0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
    0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
    0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
    0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
    0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
    0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
    0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
    0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
    0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
    0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF,
  };

  NES_DMC::NES_DMC () : GETA_BITS (20)
  {
    SetClock (DEFAULT_CLOCK);
    SetRate (DEFAULT_RATE);
    SetPal (false);
    option[OPT_ENABLE_4011] = 1;
    option[OPT_ENABLE_PNOISE] = 1;
    option[OPT_UNMUTE_ON_RESET] = 1;
    option[OPT_DPCM_ANTI_CLICK] = 0;
    option[OPT_NONLINEAR_MIXER] = 1;
    option[OPT_RANDOMIZE_NOISE] = 1;
	option[OPT_RANDOMIZE_TRI] = 1;
    option[OPT_TRI_MUTE] = 1;
    option[OPT_DPCM_REVERSE] = 0;
    tnd_table[0][0][0][0] = 0;
    tnd_table[1][0][0][0] = 0;

    apu = NULL;
    frame_sequence_count = 0;
    frame_sequence_length = 7458;
    frame_sequence_steps = 4;

    for(int c=0;c<2;++c)
        for(int t=0;t<3;++t)
            sm[c][t] = 128;
  }


  NES_DMC::~NES_DMC ()
  {
  }

  void NES_DMC::SetStereoMix(int trk, xgm::INT16 mixl, xgm::INT16 mixr)
  {
      if (trk < 0) return;
      if (trk > 2) return;
      sm[0][trk] = mixl;
      sm[1][trk] = mixr;
  }

  ITrackInfo *NES_DMC::GetTrackInfo(int trk)
  {
    switch(trk)
    {
    case 0:
      trkinfo[trk].max_volume = 255;
      trkinfo[0].key = (linear_counter>0 && length_counter[0]>0 && enable[0]);
      trkinfo[0].volume = 0;
      trkinfo[0]._freq = tri_freq;
      if(trkinfo[0]._freq)
        trkinfo[0].freq = clock/32/(trkinfo[0]._freq + 1);
      else
        trkinfo[0].freq = 0;
      trkinfo[0].tone = -1;
      trkinfo[0].output = out[0];
      break;
    case 1:
      trkinfo[1].max_volume = 15;
      trkinfo[1].volume = noise_volume+(envelope_disable?0:0x10)+(envelope_loop?0x20:0);
      trkinfo[1].key = length_counter[1]>0 && enable[1] &&
                       (envelope_disable ? (noise_volume>0) : (envelope_counter>0));
      trkinfo[1]._freq = reg[0x400e - 0x4008]&0xF;
      trkinfo[1].freq = clock/double(wavlen_table[pal][trkinfo[1]._freq] * ((noise_tap&(1<<6)) ? 93 : 1));
      trkinfo[1].tone = noise_tap & (1<<6);
      trkinfo[1].output = out[1];
      break;
    case 2:
      trkinfo[2].max_volume = 127;
      trkinfo[2].volume = reg[0x4011 - 0x4008]&0x7F;
      trkinfo[2].key = dlength > 0;
      trkinfo[2]._freq = reg[0x4010 - 0x4008]&0xF;
      trkinfo[2].freq = clock/double(freq_table[pal][trkinfo[2]._freq]);
      trkinfo[2].tone = (0xc000|(adr_reg<<6));
      trkinfo[2].output = (damp<<1)|dac_lsb;
      break;
    default:
      return NULL;
    }
    return &trkinfo[trk];
  }

  void NES_DMC::FrameSequence(int s)
  {
    //DEBUG_OUT("FrameSequence: %d\n",s);

    if (s > 3) return; // no operation in step 4

    if (apu)
    {
        apu->FrameSequence(s);
    }

    if (s == 0 && (frame_sequence_steps == 4))
    {
        if (frame_irq_enable) frame_irq = true;
        cpu->UpdateIRQ(NES_CPU::IRQD_FRAME, frame_irq & frame_irq_enable);
    }

    // 240hz clock
    {
        // triangle linear counter
        if (linear_counter_halt)
        {
            linear_counter = linear_counter_reload;
        }
        else
        {
            if (linear_counter > 0) --linear_counter;
        }
        if (!linear_counter_control)
        {
            linear_counter_halt = false;
        }

        // noise envelope
        bool divider = false;
        if (envelope_write)
        {
            envelope_write = false;
            envelope_counter = 15;
            envelope_div = 0;
        }
        else
        {
            ++envelope_div;
            if (envelope_div > envelope_div_period)
            {
                divider = true;
                envelope_div = 0;
            }
        }
        if (divider)
        {
            if (envelope_loop && envelope_counter == 0)
                envelope_counter = 15;
            else if (envelope_counter > 0)
                --envelope_counter;
        }
    }

    // 120hz clock
    if ((s&1) == 0)
    {
        // triangle length counter
        if (!linear_counter_control && (length_counter[0] > 0))
            --length_counter[0];

        // noise length counter
        if (!envelope_loop && (length_counter[1] > 0))
            --length_counter[1];
    }

  }

  // 三角波チャンネルの計算 戻り値は0-15
  UINT32 NES_DMC::calc_tri (UINT32 clocks)
  {
    static UINT32 tritbl[32] = 
    {
     15,14,13,12,11,10, 9, 8,
      7, 6, 5, 4, 3, 2, 1, 0,
      0, 1, 2, 3, 4, 5, 6, 7,
      8, 9,10,11,12,13,14,15,
    };

    if (linear_counter > 0 && length_counter[0] > 0
        && (!option[OPT_TRI_MUTE] || tri_freq > 0))
    {
      counter[0] -= clocks;
      while (counter[0] < 0)
      {
        tphase = (tphase + 1) & 31;
        counter[0] += (tri_freq + 1);
      }
    }

    UINT32 ret = tritbl[tphase];
    return ret;
  }

  // ノイズチャンネルの計算 戻り値は0-127
  // 低サンプリングレートで合成するとエイリアスノイズが激しいので
  // ノイズだけはこの関数内で高クロック合成し、簡易なサンプリングレート
  // 変換を行っている。
  UINT32 NES_DMC::calc_noise(UINT32 clocks)
  {
    UINT32 env = envelope_disable ? noise_volume : envelope_counter;
    if (length_counter[1] < 1) env = 0;

    UINT32 last = (noise & 0x4000) ? 0 : env;
    if (clocks < 1) return last;

    // simple anti-aliasing (noise requires it, even when oversampling is off)
    UINT32 count = 0;
    UINT32 accum = counter[1] * last; // samples pending from previous calc
    UINT32 accum_clocks = counter[1];
    #ifdef _DEBUG
        INT32 start_clocks = counter[1];
    #endif
    if (counter[1] < 0) // only happens on startup when using the randomize noise option
    {
        accum = 0;
        accum_clocks = 0;
    }

    counter[1] -= clocks;
    assert (nfreq > 0); // prevent infinite loop
    while (counter[1] < 0)
    {
        // tick the noise generator
        UINT32 feedback = (noise&1) ^ ((noise&noise_tap)?1:0);
        noise = (noise>>1) | (feedback<<14);

        last = (noise & 0x4000) ? 0 : env;
        accum += (last * nfreq);
        counter[1] += nfreq;
        ++count;
        accum_clocks += nfreq;
    }

    if (count < 1) // no change over interval, don't anti-alias
    {
       return last;
    }

    accum -= (last * counter[1]); // remove these samples which belong in the next calc
    accum_clocks -= counter[1];
    #ifdef _DEBUG
        if (start_clocks >= 0) assert(accum_clocks == clocks); // these should be equal
    #endif

    UINT32 average = accum / accum_clocks;
    assert(average <= 15); // above this would indicate overflow
    return average;
  }

	// Tick the DMC for the number of clocks, and return output counter;
	UINT32 NES_DMC::calc_dmc (UINT32 clocks)
	{
		counter[2] -= clocks;
		assert (dfreq > 0); // prevent infinite loop
		while (counter[2] < 0)
		{
			counter[2] += dfreq;

			if ( data > 0x100 ) // data = 0x100 when shift register is empty
			{
				if (!empty)
				{
					if ((data & 1) && (damp < 63))
						damp++;
					else if (!(data & 1) && (0 < damp))
						damp--;
				}
				data >>=1;
			}

			if ( data <= 0x100 ) // shift register is empty
			{
				if (dlength > 0)
				{
					memory->Read (daddress, data);
					cpu->StealCycles(4); // DMC read takes 3 or 4 CPU cycles, usually 4
					// (checking for the 3-cycle case would require sub-instruction emulation)
					data &= 0xFF; // read 8 bits
					if (option[OPT_DPCM_REVERSE]) data = BITREVERSE[data];
					data |= 0x10000; // use an extra bit to signal end of data
					empty = false;
					daddress = ((daddress+1)&0xFFFF)|0x8000 ;
					--dlength;
					if (dlength == 0)
					{
						if (mode & 1) // looped DPCM = auto-reload
						{
							daddress = ((adr_reg<<6)|0xC000);
							dlength = (len_reg<<4)+1;
						}
						else if (mode & 2) // IRQ and not looped
						{
							irq = true;
							cpu->UpdateIRQ(NES_CPU::IRQD_DMC, true);
						}
					}
				}
				else
				{
					data = 0x10000; // DMC will do nothing
					empty = true;
				}
			}
		}

		return (damp<<1) + dac_lsb;
	}

  void NES_DMC::TickFrameSequence (UINT32 clocks)
  {
      frame_sequence_count += clocks;
      while (frame_sequence_count > frame_sequence_length)
      {
          FrameSequence(frame_sequence_step);
          frame_sequence_count -= frame_sequence_length;
          ++frame_sequence_step;
          if(frame_sequence_step >= frame_sequence_steps)
              frame_sequence_step = 0;
      }
  }

  void NES_DMC::Tick (UINT32 clocks)
  {
    out[0] = calc_tri(clocks);
    out[1] = calc_noise(clocks);
    out[2] = calc_dmc(clocks);
  }

  UINT32 NES_DMC::Render (INT32 b[2])
  {
    out[0] = (mask & 1) ? 0 : out[0];
    out[1] = (mask & 2) ? 0 : out[1];
    out[2] = (mask & 4) ? 0 : out[2];

    INT32 m[3];
    m[0] = tnd_table[0][out[0]][0][0];
    m[1] = tnd_table[0][0][out[1]][0];
    m[2] = tnd_table[0][0][0][out[2]];

    if (option[OPT_NONLINEAR_MIXER])
    {
        INT32 ref = m[0] + m[1] + m[2];
        INT32 voltage = tnd_table[1][out[0]][out[1]][out[2]];
        if (ref)
        {
            for (int i=0; i < 3; ++i)
                m[i] = (m[i] * voltage) / ref;
        }
        else
        {
            for (int i=0; i < 3; ++i)
                m[i] = voltage;
        }
    }

    // anti-click nullifies any 4011 write but preserves nonlinearity
    if (option[OPT_DPCM_ANTI_CLICK])
    {
        if (dmc_pop) // $4011 will cause pop this frame
        {
            // adjust offset to counteract pop
            dmc_pop_offset += dmc_pop_follow - m[2];
            dmc_pop = false;

            // prevent overflow, keep headspace at edges
            const INT32 OFFSET_MAX = (1 << 30) - (4 << 16);
            if (dmc_pop_offset >  OFFSET_MAX) dmc_pop_offset =  OFFSET_MAX;
            if (dmc_pop_offset < -OFFSET_MAX) dmc_pop_offset = -OFFSET_MAX;
        }
        dmc_pop_follow = m[2]; // remember previous position

        m[2] += dmc_pop_offset; // apply offset

        // TODO implement this in a better way
        // roll off offset (not ideal, but prevents overflow)
        if (dmc_pop_offset > 0) --dmc_pop_offset;
        else if (dmc_pop_offset < 0) ++dmc_pop_offset;
    }

    b[0]  = m[0] * sm[0][0];
    b[0] += m[1] * sm[0][1];
    b[0] += m[2] * sm[0][2];
    b[0] >>= 7;

    b[1]  = m[0] * sm[1][0];
    b[1] += m[1] * sm[1][1];
    b[1] += m[2] * sm[1][2];
    b[1] >>= 7;

    return 2;
  }

  void NES_DMC::SetClock (double c)
  {
    clock = c;
  }

  void NES_DMC::SetRate (double r)
  {
    rate = (UINT32)(r?r:DEFAULT_RATE);
  }

  void NES_DMC::SetPal (bool is_pal)
  {
      pal = (is_pal ? 1 : 0);
      // set CPU cycles in frame_sequence
      frame_sequence_length = is_pal ? 8314 : 7458;
  }

  void NES_DMC::SetAPU (NES_APU* apu_)
  {
      apu = apu_;
  }

  // Initializing TRI, NOISE, DPCM mixing table
  void NES_DMC::InitializeTNDTable(double wt, double wn, double wd) {

    // volume adjusted by 0.95 based on empirical measurements
    const double MASTER = 8192.0 * 0.95;
    // truthfully, the nonlinear curve does not appear to match well
    // with my tests. Do more testing of the APU/DMC DAC later.
    // this value keeps the triangle consistent with measured levels,
    // but not necessarily the rest of this APU channel,
    // because of the lack of a good DAC model, currently.

    { // Linear Mixer
      for(int t=0; t<16 ; t++) {
        for(int n=0; n<16; n++) {
          for(int d=0; d<128; d++) {
              tnd_table[0][t][n][d] = (UINT32)(MASTER*(3.0*t+2.0*n+d)/208.0);
          }
        }
      }
    }
    { // Non-Linear Mixer
      tnd_table[1][0][0][0] = 0;
      for(int t=0; t<16 ; t++) {
        for(int n=0; n<16; n++) {
          for(int d=0; d<128; d++) {
            if(t!=0||n!=0||d!=0)
              tnd_table[1][t][n][d] = (UINT32)((MASTER*159.79)/(100.0+1.0/((double)t/wt+(double)n/wn+(double)d/wd)));
          }
        }
      }
    }

  }

  void NES_DMC::Reset ()
  {
    int i;
    mask = 0;

    InitializeTNDTable(8227,12241,22638);

    counter[0] = 0;
    counter[1] = 0;
    counter[2] = 0;
    tphase = 0;
    nfreq = wavlen_table[0][0];
    dfreq = freq_table[0][0];
    tri_freq = 0;
    linear_counter = 0;
    linear_counter_reload = 0;
    linear_counter_halt = 0;
    linear_counter_control = 0;
    noise_volume = 0;
    noise = 0;
    noise_tap = 0;
    envelope_loop = 0;
    envelope_disable = 0;
    envelope_write = 0;
    envelope_div_period = 0;
    envelope_div = 0;
    envelope_counter = 0;
    enable[0] = 0;
    enable[1] = 0;
    length_counter[0] = 0;
    length_counter[1] = 0;
    frame_irq = false;
    frame_irq_enable = false;
    frame_sequence_count = 0;
    frame_sequence_steps = 4;
    frame_sequence_step = 0;
    cpu->UpdateIRQ(NES_CPU::IRQD_FRAME, false);

    for (i = 0; i < 0x0F; i++)
      Write (0x4008 + i, 0);
    Write (0x4017, 0x40);

    irq = false;
    Write (0x4015, 0x00);
    if (option[OPT_UNMUTE_ON_RESET])
      Write (0x4015, 0x0f);
    cpu->UpdateIRQ(NES_CPU::IRQD_DMC, false);

    out[0] = out[1] = out[2] = 0;
    damp = 0;
    dmc_pop = false;
    dmc_pop_offset = 0;
    dmc_pop_follow = 0;
    dac_lsb = 0;
    data = 0x100;
    empty = true;
    adr_reg = 0;
    dlength = 0;
    len_reg = 0;
    daddress = 0;
    noise = 1;
    noise_tap = (1<<1);

    if (option[OPT_RANDOMIZE_NOISE])
    {
        noise |= ::rand();
        counter[1] = -(rand() & 511);
    }
    if (option[OPT_RANDOMIZE_TRI])
    {
        tphase = ::rand() & 31;
        counter[0] = -(rand() & 2047);
    }

    SetRate(rate);
  }

  void NES_DMC::SetMemory (IDevice * r)
  {
    memory = r;
  }

  void NES_DMC::SetOption (int id, int val)
  {
    if(id<OPT_END)
    {
      option[id] = val;
      if(id==OPT_NONLINEAR_MIXER)
        InitializeTNDTable(8227,12241,22638);
    }
  }

  bool NES_DMC::Write (UINT32 adr, UINT32 val, UINT32 id)
  {
    static const UINT8 length_table[32] = {
        0x0A, 0xFE,
        0x14, 0x02,
        0x28, 0x04,
        0x50, 0x06,
        0xA0, 0x08,
        0x3C, 0x0A,
        0x0E, 0x0C,
        0x1A, 0x0E,
        0x0C, 0x10,
        0x18, 0x12,
        0x30, 0x14,
        0x60, 0x16,
        0xC0, 0x18,
        0x48, 0x1A,
        0x10, 0x1C,
        0x20, 0x1E
    };

    if (adr == 0x4015)
    {
      enable[0] = (val & 4) ? true : false;
      enable[1] = (val & 8) ? true : false;

      if (!enable[0])
      {
          length_counter[0] = 0;
      }
      if (!enable[1])
      {
          length_counter[1] = 0;
      }

      if ((val & 16) && dlength == 0)
      {
        daddress = (0xC000 | (adr_reg << 6));
        dlength = (len_reg << 4) + 1;
      }
      else if (!(val & 16))
      {
        dlength = 0;
      }

      irq = false;
      cpu->UpdateIRQ(NES_CPU::IRQD_DMC, false);

      reg[adr-0x4008] = val;
      return true;
    }

    if (adr == 0x4017)
    {
      //DEBUG_OUT("4017 = %02X\n", val);
      frame_irq_enable = ((val & 0x40) != 0x40);
      if (frame_irq_enable) frame_irq = false;
      cpu->UpdateIRQ(NES_CPU::IRQD_FRAME, false);

      frame_sequence_count = 0;
      if (val & 0x80)
      {
        frame_sequence_steps = 5;
        frame_sequence_step = 0;
        FrameSequence(frame_sequence_step);
        ++frame_sequence_step;
      }
      else
      {
        frame_sequence_steps = 4;
        frame_sequence_step = 1;
      }
    }

    if (adr<0x4008||0x4013<adr)
      return false;

    reg[adr-0x4008] = val&0xff;

    //DEBUG_OUT("$%04X %02X\n", adr, val);

    switch (adr)
    {

    // tri

    case 0x4008:
      linear_counter_control = (val >> 7) & 1;
      linear_counter_reload = val & 0x7F;
      break;

    case 0x4009:
      break;

    case 0x400a:
      tri_freq = val | (tri_freq & 0x700) ;
      break;

    case 0x400b:
      tri_freq = (tri_freq & 0xff) | ((val & 0x7) << 8) ;
      linear_counter_halt = true;
      if (enable[0])
      {
        length_counter[0] = length_table[(val >> 3) & 0x1f];
      }
      break;

    // noise

    case 0x400c:
      noise_volume = val & 15;
      envelope_div_period = val & 15;
      envelope_disable = (val >> 4) & 1;
      envelope_loop = (val >> 5) & 1;
      break;

    case 0x400d:
      break;

    case 0x400e:
      if (option[OPT_ENABLE_PNOISE])
        noise_tap = (val & 0x80) ? (1<<6) : (1<<1);
      else
        noise_tap = (1<<1);
      nfreq = wavlen_table[pal][val&15];
      break;

    case 0x400f:
      if (enable[1])
      {
        length_counter[1] = length_table[(val >> 3) & 0x1f];
      }
      envelope_write = true;
      break;

    // dmc

    case 0x4010:
      mode = (val >> 6) & 3;
      if (!(mode & 2))
      {
        irq = false;
        cpu->UpdateIRQ(NES_CPU::IRQD_DMC, false);
      }
      dfreq = freq_table[pal][val&15];
      break;

    case 0x4011:
      if (option[OPT_ENABLE_4011])
      {
        damp = (val >> 1) & 0x3f;
        dac_lsb = val & 1;
        dmc_pop = true;
      }
      break;

    case 0x4012:
      adr_reg = val&0xff;
      // ここでdaddressは更新されない
      break;

    case 0x4013:
      len_reg = val&0xff;
      // ここでlengthは更新されない
      break;

    default:
      return false;
    }

    return true;
  }

  bool NES_DMC::Read (UINT32 adr, UINT32 & val, UINT32 id)
  {
    if (adr == 0x4015)
    {
      val |=(irq               ? 0x80 : 0)
          | (frame_irq         ? 0x40 : 0)
          | ((dlength>0)       ? 0x10 : 0)
          | (length_counter[1] ? 0x08 : 0)
          | (length_counter[0] ? 0x04 : 0)
          ;

      frame_irq = false;
      cpu->UpdateIRQ(NES_CPU::IRQD_FRAME, false);
      return true;
    }
    else if (0x4008<=adr&&adr<=0x4014)
    {
      val |= reg[adr-0x4008];
      return true;
    }
    else
      return false;
  }

  // IRQ support requires CPU read access
  void NES_DMC::SetCPU(NES_CPU* cpu_)
  {
      cpu = cpu_;
  }
} // namespace
