/*

 Yamaha YMZ280B driver
  by Aaron Giles

  YMZ280B 8-Channel PCMD8 PCM/ADPCM Decoder

 Features as listed in LSI-4MZ280B3 data sheet:
  Voice data stored in external memory can be played back simultaneously for up to eight voices
  Voice data format can be selected from 4-bit ADPCM, 8-bit PCM and 16-bit PCM
  Control of voice data external memory
   Up to 16M bytes of ROM or SRAM (x 8 bits, access time 150ms max) can be connected
   Continuous access is possible
   Loop playback between selective addresses is possible
  Voice data playback frequency control
   4-bit ADPCM ................ 0.172 to 44.1kHz in 256 steps
   8-bit PCM, 16-bit PCM ...... 0.172 to 88.2kHz in 512 steps
  256 steps total level and 16 steps panpot can be set
  Voice signal is output in stereo 16-bit 2's complement MSB-first format

*/


#include <math.h>

#include "sndintrf.h"
#include "streams.h"
#include "ymz280b.h"


#define MAX_SAMPLE_CHUNK	10000
#define MAKE_WAVS			0

#define FRAC_BITS			14
#define FRAC_ONE			(1 << FRAC_BITS)
#define FRAC_MASK			(FRAC_ONE - 1)

#define INTERNAL_BUFFER_SIZE 	(1 << 15)
#define INTERNAL_SAMPLE_RATE 	(chip->master_clock * 2.0)

#if MAKE_WAVS
#include "wavwrite.h"
#endif


/* struct describing a single playing ADPCM voice */
struct YMZ280BVoice
{
	UINT8 playing;			/* 1 if we are actively playing */

	UINT8 keyon;			/* 1 if the key is on */
	UINT8 looping;			/* 1 if looping is enabled */
	UINT8 mode;				/* current playback mode */
	UINT16 fnum;			/* frequency */
	UINT8 level;			/* output level */
	UINT8 pan;				/* panning */

	UINT32 start;			/* start address, in nibbles */
	UINT32 stop;			/* stop address, in nibbles */
	UINT32 loop_start;		/* loop start address, in nibbles */
	UINT32 loop_end;		/* loop end address, in nibbles */
	UINT32 position;		/* current position, in nibbles */

	INT32 signal;			/* current ADPCM signal */
	INT32 step;				/* current ADPCM step */

	INT32 loop_signal;		/* signal at loop start */
	INT32 loop_step;		/* step at loop start */
	UINT32 loop_count;		/* number of loops so far */

	INT32 output_left;		/* output volume (left) */
	INT32 output_right;		/* output volume (right) */
	INT32 output_step;		/* step value for frequency conversion */
	INT32 output_pos;		/* current fractional position */
	INT16 last_sample;		/* last sample output */
	INT16 curr_sample;		/* current sample target */
	UINT8 irq_schedule;		/* 1 if the IRQ state is updated by timer */
};

typedef struct _ymz280b_state ymz280b_state;
struct _ymz280b_state
{
	sound_stream * stream;			/* which stream are we using */
	UINT8 *region_base;				/* pointer to the base of the region */
	UINT8 current_register;			/* currently accessible register */
	UINT8 status_register;			/* current status register */
	UINT8 irq_state;				/* current IRQ state */
	UINT8 irq_mask;					/* current IRQ mask */
	UINT8 irq_enable;				/* current IRQ enable */
	UINT8 keyon_enable;				/* key on enable */
	double master_clock;			/* master clock frequency */
	void (*irq_callback)(const device_config *, int);		/* IRQ callback */
	struct YMZ280BVoice	voice[8];	/* the 8 voices */
	UINT32 rom_readback_addr;		/* where the CPU can read the ROM */
	devcb_resolved_read8 ext_ram_read;		/* external RAM read handler */
	devcb_resolved_write8 ext_ram_write;	/* external RAM write handler */

#if MAKE_WAVS
	void *		wavresample;			/* resampled waveform */
#endif

	INT16 *scratch;
	const device_config *device;
};

/* step size index shift table */
static const int index_scale[8] = { 0x0e6, 0x0e6, 0x0e6, 0x0e6, 0x133, 0x199, 0x200, 0x266 };

/* lookup table for the precomputed difference */
static int diff_lookup[16];

/* timer callback */
static TIMER_CALLBACK( update_irq_state_timer_0 );
static TIMER_CALLBACK( update_irq_state_timer_1 );
static TIMER_CALLBACK( update_irq_state_timer_2 );
static TIMER_CALLBACK( update_irq_state_timer_3 );
static TIMER_CALLBACK( update_irq_state_timer_4 );
static TIMER_CALLBACK( update_irq_state_timer_5 );
static TIMER_CALLBACK( update_irq_state_timer_6 );
static TIMER_CALLBACK( update_irq_state_timer_7 );

static const timer_fired_func update_irq_state_cb[] =
{
	update_irq_state_timer_0,
	update_irq_state_timer_1,
	update_irq_state_timer_2,
	update_irq_state_timer_3,
	update_irq_state_timer_4,
	update_irq_state_timer_5,
	update_irq_state_timer_6,
	update_irq_state_timer_7
};


INLINE ymz280b_state *get_safe_token(const device_config *device)
{
	assert(device != NULL);
	assert(device->token != NULL);
	assert(device->type == SOUND);
	assert(sound_get_type(device) == SOUND_YMZ280B);
	return (ymz280b_state *)device->token;
}


INLINE void update_irq_state(ymz280b_state *chip)
{
	int irq_bits = chip->status_register & chip->irq_mask;

	/* always off if the enable is off */
	if (!chip->irq_enable)
		irq_bits = 0;

	/* update the state if changed */
	if (irq_bits && !chip->irq_state)
	{
		chip->irq_state = 1;
		if (chip->irq_callback)
			(*chip->irq_callback)(chip->device, 1);
		else logerror("YMZ280B: IRQ generated, but no callback specified!");
	}
	else if (!irq_bits && chip->irq_state)
	{
		chip->irq_state = 0;
		if (chip->irq_callback)
			(*chip->irq_callback)(chip->device, 0);
		else logerror("YMZ280B: IRQ generated, but no callback specified!");
	}
}


INLINE void update_step(ymz280b_state *chip, struct YMZ280BVoice *voice)
{
	double frequency;

	/* compute the frequency */
	if (voice->mode == 1)
		frequency = chip->master_clock * (double)((voice->fnum & 0x0ff) + 1) * (1.0 / 256.0);
	else
		frequency = chip->master_clock * (double)((voice->fnum & 0x1ff) + 1) * (1.0 / 256.0);
	voice->output_step = (UINT32)(frequency * (double)FRAC_ONE / INTERNAL_SAMPLE_RATE);
}


INLINE void update_volumes(struct YMZ280BVoice *voice)
{
	if (voice->pan == 8)
	{
		voice->output_left = voice->level;
		voice->output_right = voice->level;
	}
	else if (voice->pan < 8)
	{
		voice->output_left = voice->level;
		voice->output_right = voice->level * voice->pan / 8;
	}
	else
	{
		voice->output_left = voice->level * (15 - voice->pan) / 8;
		voice->output_right = voice->level;
	}
}


static STATE_POSTLOAD( YMZ280B_state_save_update_step )
{
	ymz280b_state *chip = (ymz280b_state *)param;
	int j;
	for (j = 0; j < 8; j++)
	{
		struct YMZ280BVoice *voice = &chip->voice[j];
		update_step(chip, voice);
		if(voice->irq_schedule)
			timer_set(machine, attotime_zero, chip, 0, update_irq_state_cb[j]);
	}
}


static void update_irq_state_timer_common(void *param, int voicenum)
{
	ymz280b_state *chip = (ymz280b_state *)param;
	struct YMZ280BVoice *voice = &chip->voice[voicenum];

	if(!voice->irq_schedule) return;

	voice->playing = 0;
	chip->status_register |= 1 << voicenum;
	update_irq_state(chip);
	voice->irq_schedule = 0;
}

static TIMER_CALLBACK( update_irq_state_timer_0 ) { update_irq_state_timer_common(ptr, 0); }
static TIMER_CALLBACK( update_irq_state_timer_1 ) { update_irq_state_timer_common(ptr, 1); }
static TIMER_CALLBACK( update_irq_state_timer_2 ) { update_irq_state_timer_common(ptr, 2); }
static TIMER_CALLBACK( update_irq_state_timer_3 ) { update_irq_state_timer_common(ptr, 3); }
static TIMER_CALLBACK( update_irq_state_timer_4 ) { update_irq_state_timer_common(ptr, 4); }
static TIMER_CALLBACK( update_irq_state_timer_5 ) { update_irq_state_timer_common(ptr, 5); }
static TIMER_CALLBACK( update_irq_state_timer_6 ) { update_irq_state_timer_common(ptr, 6); }
static TIMER_CALLBACK( update_irq_state_timer_7 ) { update_irq_state_timer_common(ptr, 7); }


/**********************************************************************************************

     compute_tables -- compute the difference tables

***********************************************************************************************/

static void compute_tables(void)
{
	int nib;

	/* loop over all nibbles and compute the difference */
	for (nib = 0; nib < 16; nib++)
	{
		int value = (nib & 0x07) * 2 + 1;
		diff_lookup[nib] = (nib & 0x08) ? -value : value;
	}
}



/**********************************************************************************************

     generate_adpcm -- general ADPCM decoding routine

***********************************************************************************************/

static int generate_adpcm(struct YMZ280BVoice *voice, UINT8 *base, INT16 *buffer, int samples)
{
	int position = voice->position;
	int signal = voice->signal;
	int step = voice->step;
	int val;

	/* two cases: first cases is non-looping */
	if (!voice->looping)
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* compute the new amplitude and update the current step */
			val = base[position / 2] >> ((~position & 1) << 2);
			signal += (step * diff_lookup[val & 15]) / 8;

			/* clamp to the maximum */
			if (signal > 32767)
				signal = 32767;
			else if (signal < -32768)
				signal = -32768;

			/* adjust the step size and clamp */
			step = (step * index_scale[val & 7]) >> 8;
			if (step > 0x6000)
				step = 0x6000;
			else if (step < 0x7f)
				step = 0x7f;

			/* output to the buffer, scaling by the volume */
			*buffer++ = signal;
			samples--;

			/* next! */
			position++;
			if (position >= voice->stop)
				break;
		}
	}

	/* second case: looping */
	else
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* compute the new amplitude and update the current step */
			val = base[position / 2] >> ((~position & 1) << 2);
			signal += (step * diff_lookup[val & 15]) / 8;

			/* clamp to the maximum */
			if (signal > 32767)
				signal = 32767;
			else if (signal < -32768)
				signal = -32768;

			/* adjust the step size and clamp */
			step = (step * index_scale[val & 7]) >> 8;
			if (step > 0x6000)
				step = 0x6000;
			else if (step < 0x7f)
				step = 0x7f;

			/* output to the buffer, scaling by the volume */
			*buffer++ = signal;
			samples--;

			/* next! */
			position++;
			if (position == voice->loop_start && voice->loop_count == 0)
			{
				voice->loop_signal = signal;
				voice->loop_step = step;
			}
			if (position >= voice->loop_end)
			{
				if (voice->keyon)
				{
					position = voice->loop_start;
					signal = voice->loop_signal;
					step = voice->loop_step;
					voice->loop_count++;
				}
			}
			if (position >= voice->stop)
				break;
		}
	}

	/* update the parameters */
	voice->position = position;
	voice->signal = signal;
	voice->step = step;

	return samples;
}



/**********************************************************************************************

     generate_pcm8 -- general 8-bit PCM decoding routine

***********************************************************************************************/

static int generate_pcm8(struct YMZ280BVoice *voice, UINT8 *base, INT16 *buffer, int samples)
{
	int position = voice->position;
	int val;

	/* two cases: first cases is non-looping */
	if (!voice->looping)
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* fetch the current value */
			val = base[position / 2];

			/* output to the buffer, scaling by the volume */
			*buffer++ = (INT8)val * 256;
			samples--;

			/* next! */
			position += 2;
			if (position >= voice->stop)
				break;
		}
	}

	/* second case: looping */
	else
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* fetch the current value */
			val = base[position / 2];

			/* output to the buffer, scaling by the volume */
			*buffer++ = (INT8)val * 256;
			samples--;

			/* next! */
			position += 2;
			if (position >= voice->loop_end)
			{
				if (voice->keyon)
					position = voice->loop_start;
			}
			if (position >= voice->stop)
				break;
		}
	}

	/* update the parameters */
	voice->position = position;

	return samples;
}



/**********************************************************************************************

     generate_pcm16 -- general 16-bit PCM decoding routine

***********************************************************************************************/

static int generate_pcm16(struct YMZ280BVoice *voice, UINT8 *base, INT16 *buffer, int samples)
{
	int position = voice->position;
	int val;

	/* two cases: first cases is non-looping */
	if (!voice->looping)
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* fetch the current value */
			val = (INT16)((base[position / 2 + 1] << 8) + base[position / 2]);

			/* output to the buffer, scaling by the volume */
			*buffer++ = val;
			samples--;

			/* next! */
			position += 4;
			if (position >= voice->stop)
				break;
		}
	}

	/* second case: looping */
	else
	{
		/* loop while we still have samples to generate */
		while (samples)
		{
			/* fetch the current value */
			val = (INT16)((base[position / 2 + 1] << 8) + base[position / 2]);

			/* output to the buffer, scaling by the volume */
			*buffer++ = val;
			samples--;

			/* next! */
			position += 4;
			if (position >= voice->loop_end)
			{
				if (voice->keyon)
					position = voice->loop_start;
			}
			if (position >= voice->stop)
				break;
		}
	}

	/* update the parameters */
	voice->position = position;

	return samples;
}



/**********************************************************************************************

     ymz280b_update -- update the sound chip so that it is in sync with CPU execution

***********************************************************************************************/

static STREAM_UPDATE( ymz280b_update )
{
	ymz280b_state *chip = (ymz280b_state *)param;
	stream_sample_t *lacc = outputs[0];
	stream_sample_t *racc = outputs[1];
	int v;

	/* clear out the accumulator */
	memset(lacc, 0, samples * sizeof(lacc[0]));
	memset(racc, 0, samples * sizeof(racc[0]));

	/* loop over voices */
	for (v = 0; v < 8; v++)
	{
		struct YMZ280BVoice *voice = &chip->voice[v];
		INT16 prev = voice->last_sample;
		INT16 curr = voice->curr_sample;
		INT16 *curr_data = chip->scratch;
		INT32 *ldest = lacc;
		INT32 *rdest = racc;
		UINT32 new_samples, samples_left;
		UINT32 final_pos;
		int remaining = samples;
		int lvol = voice->output_left;
		int rvol = voice->output_right;

		/* quick out if we're not playing and we're at 0 */
		if (!voice->playing && curr == 0)
			continue;

		/* finish off the current sample */
//      if (voice->output_pos > 0)
		{
			/* interpolate */
			while (remaining > 0 && voice->output_pos < FRAC_ONE)
			{
				int interp_sample = (((INT32)prev * (FRAC_ONE - voice->output_pos)) + ((INT32)curr * voice->output_pos)) >> FRAC_BITS;
				*ldest++ += interp_sample * lvol;
				*rdest++ += interp_sample * rvol;
				voice->output_pos += voice->output_step;
				remaining--;
			}

			/* if we're over, continue; otherwise, we're done */
			if (voice->output_pos >= FRAC_ONE)
				voice->output_pos -= FRAC_ONE;
			else
				continue;
		}

		/* compute how many new samples we need */
		final_pos = voice->output_pos + remaining * voice->output_step;
		new_samples = (final_pos + FRAC_ONE) >> FRAC_BITS;
		if (new_samples > MAX_SAMPLE_CHUNK)
			new_samples = MAX_SAMPLE_CHUNK;
		samples_left = new_samples;

		/* generate them into our buffer */
		if (voice->playing)
		{
			switch (voice->mode)
			{
				case 1:	samples_left = generate_adpcm(voice, chip->region_base, chip->scratch, new_samples);	break;
				case 2:	samples_left = generate_pcm8(voice, chip->region_base, chip->scratch, new_samples);	break;
				case 3:	samples_left = generate_pcm16(voice, chip->region_base, chip->scratch, new_samples);	break;
				default:
				case 0:	samples_left = 0; memset(chip->scratch, 0, new_samples * sizeof(chip->scratch[0]));			break;
			}
		}

		/* if there are leftovers, ramp back to 0 */
		if (samples_left)
		{
			int base = new_samples - samples_left;
			int i, t = (base == 0) ? curr : chip->scratch[base - 1];
			for (i = 0; i < samples_left; i++)
			{
				if (t < 0) t = -((-t * 15) >> 4);
				else if (t > 0) t = (t * 15) >> 4;
				chip->scratch[base + i] = t;
			}

			/* if we hit the end and IRQs are enabled, signal it */
			if (base != 0)
			{
				voice->playing = 0;

				/* set update_irq_state_timer. IRQ is signaled on next CPU execution. */
				timer_set(chip->device->machine, attotime_zero, chip, 0, update_irq_state_cb[v]);
				voice->irq_schedule = 1;
			}
		}

		/* advance forward one sample */
		prev = curr;
		curr = *curr_data++;

		/* then sample-rate convert with linear interpolation */
		while (remaining > 0)
		{
			/* interpolate */
			while (remaining > 0 && voice->output_pos < FRAC_ONE)
			{
				int interp_sample = (((INT32)prev * (FRAC_ONE - voice->output_pos)) + ((INT32)curr * voice->output_pos)) >> FRAC_BITS;
				*ldest++ += interp_sample * lvol;
				*rdest++ += interp_sample * rvol;
				voice->output_pos += voice->output_step;
				remaining--;
			}

			/* if we're over, grab the next samples */
			if (voice->output_pos >= FRAC_ONE)
			{
				voice->output_pos -= FRAC_ONE;
				prev = curr;
				curr = *curr_data++;
			}
		}

		/* remember the last samples */
		voice->last_sample = prev;
		voice->curr_sample = curr;
	}

	for (v = 0; v < samples; v++)
	{
		outputs[0][v] /= 256;
		outputs[1][v] /= 256;
	}
}



/**********************************************************************************************

     DEVICE_START( ymz280b ) -- start emulation of the YMZ280B

***********************************************************************************************/

static DEVICE_START( ymz280b )
{
	static const ymz280b_interface defintrf = { 0 };
	const ymz280b_interface *intf = (device->static_config != NULL) ? (const ymz280b_interface *)device->static_config : &defintrf;
	ymz280b_state *chip = get_safe_token(device);

	chip->device = device;
	devcb_resolve_read8(&chip->ext_ram_read, &intf->ext_read, device);
	devcb_resolve_write8(&chip->ext_ram_write, &intf->ext_write, device);

	/* compute ADPCM tables */
	compute_tables();

	/* initialize the rest of the structure */
	chip->master_clock = (double)device->clock / 384.0;
	chip->region_base = device->region;
	chip->irq_callback = intf->irq_callback;

	/* create the stream */
	chip->stream = stream_create(device, 0, 2, INTERNAL_SAMPLE_RATE, chip, ymz280b_update);

	/* allocate memory */
	chip->scratch = auto_alloc_array(device->machine, INT16, MAX_SAMPLE_CHUNK);

	/* state save */
	{
		int j;
		state_save_register_device_item(device, 0, chip->current_register);
		state_save_register_device_item(device, 0, chip->status_register);
		state_save_register_device_item(device, 0, chip->irq_state);
		state_save_register_device_item(device, 0, chip->irq_mask);
		state_save_register_device_item(device, 0, chip->irq_enable);
		state_save_register_device_item(device, 0, chip->keyon_enable);
		state_save_register_device_item(device, 0, chip->rom_readback_addr);
		for (j = 0; j < 8; j++)
		{
			state_save_register_device_item(device, j, chip->voice[j].playing);
			state_save_register_device_item(device, j, chip->voice[j].keyon);
			state_save_register_device_item(device, j, chip->voice[j].looping);
			state_save_register_device_item(device, j, chip->voice[j].mode);
			state_save_register_device_item(device, j, chip->voice[j].fnum);
			state_save_register_device_item(device, j, chip->voice[j].level);
			state_save_register_device_item(device, j, chip->voice[j].pan);
			state_save_register_device_item(device, j, chip->voice[j].start);
			state_save_register_device_item(device, j, chip->voice[j].stop);
			state_save_register_device_item(device, j, chip->voice[j].loop_start);
			state_save_register_device_item(device, j, chip->voice[j].loop_end);
			state_save_register_device_item(device, j, chip->voice[j].position);
			state_save_register_device_item(device, j, chip->voice[j].signal);
			state_save_register_device_item(device, j, chip->voice[j].step);
			state_save_register_device_item(device, j, chip->voice[j].loop_signal);
			state_save_register_device_item(device, j, chip->voice[j].loop_step);
			state_save_register_device_item(device, j, chip->voice[j].loop_count);
			state_save_register_device_item(device, j, chip->voice[j].output_left);
			state_save_register_device_item(device, j, chip->voice[j].output_right);
			state_save_register_device_item(device, j, chip->voice[j].output_pos);
			state_save_register_device_item(device, j, chip->voice[j].last_sample);
			state_save_register_device_item(device, j, chip->voice[j].curr_sample);
			state_save_register_device_item(device, j, chip->voice[j].irq_schedule);
		}
	}

	state_save_register_postload(device->machine, YMZ280B_state_save_update_step, chip);

#if MAKE_WAVS
	chip->wavresample = wav_open("resamp.wav", INTERNAL_SAMPLE_RATE, 2);
#endif
}



/**********************************************************************************************

     write_to_register -- handle a write to the current register

***********************************************************************************************/

static void write_to_register(ymz280b_state *chip, int data)
{
	struct YMZ280BVoice *voice;
	int i;

	/* force an update */
	stream_update(chip->stream);

	/* lower registers follow a pattern */
	if (chip->current_register < 0x80)
	{
		voice = &chip->voice[(chip->current_register >> 2) & 7];

		switch (chip->current_register & 0xe3)
		{
			case 0x00:		/* pitch low 8 bits */
				voice->fnum = (voice->fnum & 0x100) | (data & 0xff);
				update_step(chip, voice);
				break;

			case 0x01:		/* pitch upper 1 bit, loop, key on, mode */
				voice->fnum = (voice->fnum & 0xff) | ((data & 0x01) << 8);
				voice->looping = (data & 0x10) >> 4;
				voice->mode = (data & 0x60) >> 5;
				if (!voice->keyon && (data & 0x80) && chip->keyon_enable)
				{
					voice->playing = 1;
					voice->position = voice->start;
					voice->signal = voice->loop_signal = 0;
					voice->step = voice->loop_step = 0x7f;
					voice->loop_count = 0;

					/* if update_irq_state_timer is set, cancel it. */
					voice->irq_schedule = 0;
				}
				if (voice->keyon && !(data & 0x80) && !voice->looping)
				{
					voice->playing = 0;

					/* if update_irq_state_timer is set, cancel it. */
					voice->irq_schedule = 0;
				}
				voice->keyon = (data & 0x80) >> 7;
				update_step(chip, voice);
				break;

			case 0x02:		/* total level */
				voice->level = data;
				update_volumes(voice);
				break;

			case 0x03:		/* pan */
				voice->pan = data & 0x0f;
				update_volumes(voice);
				break;

			case 0x20:		/* start address high */
				voice->start = (voice->start & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x21:		/* loop start address high */
				voice->loop_start = (voice->loop_start & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x22:		/* loop end address high */
				voice->loop_end = (voice->loop_end & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x23:		/* stop address high */
				voice->stop = (voice->stop & (0x00ffff << 1)) | (data << 17);
				break;

			case 0x40:		/* start address middle */
				voice->start = (voice->start & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x41:		/* loop start address middle */
				voice->loop_start = (voice->loop_start & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x42:		/* loop end address middle */
				voice->loop_end = (voice->loop_end & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x43:		/* stop address middle */
				voice->stop = (voice->stop & (0xff00ff << 1)) | (data << 9);
				break;

			case 0x60:		/* start address low */
				voice->start = (voice->start & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x61:		/* loop start address low */
				voice->loop_start = (voice->loop_start & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x62:		/* loop end address low */
				voice->loop_end = (voice->loop_end & (0xffff00 << 1)) | (data << 1);
				break;

			case 0x63:		/* stop address low */
				voice->stop = (voice->stop & (0xffff00 << 1)) | (data << 1);
				break;

			default:
				logerror("YMZ280B: unknown register write %02X = %02X\n", chip->current_register, data);
				break;
		}
	}

	/* upper registers are special */
	else
	{
		switch (chip->current_register)
		{
			case 0x84:		/* ROM readback / RAM write (high) */
				chip->rom_readback_addr &= 0xffff;
				chip->rom_readback_addr |= (data<<16);
				break;

			case 0x85:		/* ROM readback / RAM write (med) */
				chip->rom_readback_addr &= 0xff00ff;
				chip->rom_readback_addr |= (data<<8);
				break;

			case 0x86:		/* ROM readback / RAM write (low) */
				chip->rom_readback_addr &= 0xffff00;
				chip->rom_readback_addr |= data;
				break;

			case 0x87:		/* RAM write */
				if (chip->ext_ram_write.write)
					devcb_call_write8(&chip->ext_ram_write, chip->rom_readback_addr, data);
				else
					logerror("YMZ280B attempted RAM write to %X\n", chip->rom_readback_addr);
				break;

			case 0xfe:		/* IRQ mask */
				chip->irq_mask = data;
				update_irq_state(chip);
				break;

			case 0xff:		/* IRQ enable, test, etc */
				chip->irq_enable = (data & 0x10) >> 4;
				update_irq_state(chip);

				if (chip->keyon_enable && !(data & 0x80))
				{
					for (i = 0; i < 8; i++)
					{
						chip->voice[i].playing = 0;

						/* if update_irq_state_timer is set, cancel it. */
						chip->voice[i].irq_schedule = 0;
					}
				}
				else if (!chip->keyon_enable && (data & 0x80))
				{
					for (i = 0; i < 8; i++)
					{
						if (chip->voice[i].keyon && chip->voice[i].looping)
							chip->voice[i].playing = 1;
					}
				}
				chip->keyon_enable = (data & 0x80) >> 7;
				break;

			default:
				logerror("YMZ280B: unknown register write %02X = %02X\n", chip->current_register, data);
				break;
		}
	}
}



/**********************************************************************************************

     compute_status -- determine the status bits

***********************************************************************************************/

static int compute_status(ymz280b_state *chip)
{
	UINT8 result;

	/* ROM/RAM readback? */
	if (chip->current_register == 0x86)
	{
		return chip->region_base[chip->rom_readback_addr];
	}

	/* force an update */
	stream_update(chip->stream);

	result = chip->status_register;

	/* clear the IRQ state */
	chip->status_register = 0;
	update_irq_state(chip);

	return result;
}



/**********************************************************************************************

     ymz280b_status_0_r/ymz280b_status_1_r -- handle a read from the status register

***********************************************************************************************/

READ8_DEVICE_HANDLER( ymz280b_r )
{
	ymz280b_state *chip = get_safe_token(device);

	if ((offset & 1) == 0)
		return devcb_call_read8(&chip->ext_ram_read, chip->rom_readback_addr++ - 1);
	else
		return compute_status(chip);
}


WRITE8_DEVICE_HANDLER( ymz280b_w )
{
	ymz280b_state *chip = get_safe_token(device);

	if ((offset & 1) == 0)
		chip->current_register = data;
	else
		write_to_register(chip, data);
}



/**************************************************************************
 * Generic get_info
 **************************************************************************/

DEVICE_GET_INFO( ymz280b )
{
	switch (state)
	{
		/* --- the following bits of info are returned as 64-bit signed integers --- */
		case DEVINFO_INT_TOKEN_BYTES:					info->i = sizeof(ymz280b_state);			break;

		/* --- the following bits of info are returned as pointers to data or functions --- */
		case DEVINFO_FCT_START:							info->start = DEVICE_START_NAME( ymz280b );		break;
		case DEVINFO_FCT_STOP:							/* Nothing */									break;
		case DEVINFO_FCT_RESET:							/* Nothing */									break;

		/* --- the following bits of info are returned as NULL-terminated strings --- */
		case DEVINFO_STR_NAME:							strcpy(info->s, "YMZ280B");						break;
		case DEVINFO_STR_FAMILY:					strcpy(info->s, "Yamaha Wavetable");			break;
		case DEVINFO_STR_VERSION:					strcpy(info->s, "1.0");							break;
		case DEVINFO_STR_SOURCE_FILE:						strcpy(info->s, __FILE__);						break;
		case DEVINFO_STR_CREDITS:					strcpy(info->s, "Copyright Nicola Salmoria and the MAME Team"); break;
	}
}

