tml; charset=UTF-8 Last-Modified: Fri, 02 May 2025 17:25:12 GMT Expires: Mon, 30 Apr 2035 17:25:12 GMT cleanup toshiba 1000 backup RAM device (nw) - hbmame - Emulator of homebrew and hacked games for arcade hardware
summaryrefslogtreecommitdiffstats
path: root/android-project
diff options
context:
space:
mode:
author Vas Crabb <vas@vastheman.com>2018-01-05 20:54:33 +1100
committer Vas Crabb <vas@vastheman.com>2018-01-05 20:55:05 +1100
commit0335ff7676e0408898468760ef3636e9283d659e (patch)
treea10eb6ecaae0239ec24377acf262ba46b4d46600 /android-project
parentc28c7b92690eb6aaa6c0e91b60cea787883f0789 (diff)
cleanup toshiba 1000 backup RAM device (nw)
Diffstat (limited to 'android-project')
0 files changed, 0 insertions, 0 deletions
'n20' href='#n20'>20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
// license:???
// copyright-holders:Anthony Kruize
/**************************************************************************************
* Game Boy sound emulation (c) Anthony Kruize (trandor@labyrinth.net.au)
*
* Anyways, sound on the Game Boy consists of 4 separate 'channels'
*   Sound1 = Quadrangular waves with SWEEP and ENVELOPE functions  (NR10,11,12,13,14)
*   Sound2 = Quadrangular waves with ENVELOPE functions (NR21,22,23,24)
*   Sound3 = Wave patterns from WaveRAM (NR30,31,32,33,34)
*   Sound4 = White noise with an envelope (NR41,42,43,44)
*
* Each sound channel has 2 modes, namely ON and OFF...  whoa
*
* These tend to be the two most important equations in
* converting between Hertz and GB frequency registers:
* (Sounds will have a 2.4% higher frequency on Super GB.)
*       gb = 2048 - (131072 / Hz)
*       Hz = 131072 / (2048 - gb)
*
* Changes:
*
*   10/2/2002       AK - Preliminary sound code.
*   13/2/2002       AK - Added a hack for mode 4, other fixes.
*   23/2/2002       AK - Use lookup tables, added sweep to mode 1. Re-wrote the square
*                        wave generation.
*   13/3/2002       AK - Added mode 3, better lookup tables, other adjustments.
*   15/3/2002       AK - Mode 4 can now change frequencies.
*   31/3/2002       AK - Accidently forgot to handle counter/consecutive for mode 1.
*    3/4/2002       AK - Mode 1 sweep can still occur if shift is 0.  Don't let frequency
*                        go past the maximum allowed value. Fixed Mode 3 length table.
*                        Slight adjustment to Mode 4's period table generation.
*    5/4/2002       AK - Mode 4 is done correctly, using a polynomial counter instead
*                        of being a total hack.
*    6/4/2002       AK - Slight tweak to mode 3's frequency calculation.
*   13/4/2002       AK - Reset envelope value when sound is initialized.
*   21/4/2002       AK - Backed out the mode 3 frequency calculation change.
*                        Merged init functions into gameboy_sound_w().
*   14/5/2002       AK - Removed magic numbers in the fixed point math.
*   12/6/2002       AK - Merged SOUNDx structs into one SOUND struct.
*  26/10/2002       AK - Finally fixed channel 3!
*
***************************************************************************************/

#include "emu.h"
#include "gb.h"


/***************************************************************************
    CONSTANTS
***************************************************************************/

#define NR10 0x00
#define NR11 0x01
#define NR12 0x02
#define NR13 0x03
#define NR14 0x04
#define NR21 0x06
#define NR22 0x07
#define NR23 0x08
#define NR24 0x09
#define NR30 0x0A
#define NR31 0x0B
#define NR32 0x0C
#define NR33 0x0D
#define NR34 0x0E
#define NR41 0x10
#define NR42 0x11
#define NR43 0x12
#define NR44 0x13
#define NR50 0x14
#define NR51 0x15
#define NR52 0x16
#define AUD3W0 0x20
#define AUD3W1 0x21
#define AUD3W2 0x22
#define AUD3W3 0x23
#define AUD3W4 0x24
#define AUD3W5 0x25
#define AUD3W6 0x26
#define AUD3W7 0x27
#define AUD3W8 0x28
#define AUD3W9 0x29
#define AUD3WA 0x2A
#define AUD3WB 0x2B
#define AUD3WC 0x2C
#define AUD3WD 0x2D
#define AUD3WE 0x2E
#define AUD3WF 0x2F

#define LEFT 1
#define RIGHT 2
#define FIXED_POINT 16

/* Represents wave duties of 12.5%, 25%, 50% and 75% */
static const float wave_duty_table[4] = { 8.0f, 4.0f, 2.0f, 1.33f };

// device type definition
const device_type GAMEBOY = &device_creator<gameboy_sound_device>;

//**************************************************************************
//  LIVE DEVICE
//**************************************************************************

//-------------------------------------------------
//  gameboy_sound_device - constructor
//-------------------------------------------------

gameboy_sound_device::gameboy_sound_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
					: device_t(mconfig, GAMEBOY, "LR35902 Sound", tag, owner, clock, "gameboy_sound", __FILE__),
						device_sound_interface(mconfig, *this)
{
}

//-------------------------------------------------
//  device_config_complete - perform any
//  operations now that the configuration is
//  complete
//-------------------------------------------------

void gameboy_sound_device::device_config_complete()
{
}

//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

void gameboy_sound_device::device_start()
{
	m_channel = machine().sound().stream_alloc(*this, 0, 2, machine().sample_rate());
	m_rate = machine().sample_rate();

	save_item(NAME(m_snd_regs));
	// sound control
	save_item(NAME(m_snd_control.on));
	save_item(NAME(m_snd_control.vol_left));
	save_item(NAME(m_snd_control.vol_right));
	save_item(NAME(m_snd_control.mode1_left));
	save_item(NAME(m_snd_control.mode1_right));
	save_item(NAME(m_snd_control.mode2_left));
	save_item(NAME(m_snd_control.mode2_right));
	save_item(NAME(m_snd_control.mode3_left));
	save_item(NAME(m_snd_control.mode3_right));
	save_item(NAME(m_snd_control.mode4_left));
	save_item(NAME(m_snd_control.mode4_right));
	// sound 1
	save_item(NAME(m_snd_1.on));
	save_item(NAME(m_snd_1.channel));
	save_item(NAME(m_snd_1.length));
	save_item(NAME(m_snd_1.pos));
	save_item(NAME(m_snd_1.period));
	save_item(NAME(m_snd_1.count));
	save_item(NAME(m_snd_1.mode));
	save_item(NAME(m_snd_1.duty));
	save_item(NAME(m_snd_1.env_value));
	save_item(NAME(m_snd_1.env_direction));
	save_item(NAME(m_snd_1.env_length));
	save_item(NAME(m_snd_1.env_count));
	save_item(NAME(m_snd_1.signal));
	save_item(NAME(m_snd_1.frequency));
	save_item(NAME(m_snd_1.swp_shift));
	save_item(NAME(m_snd_1.swp_direction));
	save_item(NAME(m_snd_1.swp_time));
	save_item(NAME(m_snd_1.swp_count));
	save_item(NAME(m_snd_1.level));
	save_item(NAME(m_snd_1.offset));
	save_item(NAME(m_snd_1.dutycount));
	save_item(NAME(m_snd_1.ply_step));
	save_item(NAME(m_snd_1.ply_value));
	// sound 2
	save_item(NAME(m_snd_2.on));
	save_item(NAME(m_snd_2.channel));
	save_item(NAME(m_snd_2.length));
	save_item(NAME(m_snd_2.pos));
	save_item(NAME(m_snd_2.period));
	save_item(NAME(m_snd_2.count));
	save_item(NAME(m_snd_2.mode));
	save_item(NAME(m_snd_2.duty));
	save_item(NAME(m_snd_2.env_value));
	save_item(NAME(m_snd_2.env_direction));
	save_item(NAME(m_snd_2.env_length));
	save_item(NAME(m_snd_2.env_count));
	save_item(NAME(m_snd_2.signal));
	save_item(NAME(m_snd_2.frequency));
	save_item(NAME(m_snd_2.swp_shift));
	save_item(NAME(m_snd_2.swp_direction));
	save_item(NAME(m_snd_2.swp_time));
	save_item(NAME(m_snd_2.swp_count));
	save_item(NAME(m_snd_2.level));
	save_item(NAME(m_snd_2.offset));
	save_item(NAME(m_snd_2.dutycount));
	save_item(NAME(m_snd_2.ply_step));
	save_item(NAME(m_snd_2.ply_value));
	// sound 3
	save_item(NAME(m_snd_3.on));
	save_item(NAME(m_snd_3.channel));
	save_item(NAME(m_snd_3.length));
	save_item(NAME(m_snd_3.pos));
	save_item(NAME(m_snd_3.period));
	save_item(NAME(m_snd_3.count));
	save_item(NAME(m_snd_3.mode));
	save_item(NAME(m_snd_3.duty));
	save_item(NAME(m_snd_3.env_value));
	save_item(NAME(m_snd_3.env_direction));
	save_item(NAME(m_snd_3.env_length));
	save_item(NAME(m_snd_3.env_count));
	save_item(NAME(m_snd_3.signal));
	save_item(NAME(m_snd_3.frequency));
	save_item(NAME(m_snd_3.swp_shift));
	save_item(NAME(m_snd_3.swp_direction));
	save_item(NAME(m_snd_3.swp_time));
	save_item(NAME(m_snd_3.swp_count));
	save_item(NAME(m_snd_3.level));
	save_item(NAME(m_snd_3.offset));
	save_item(NAME(m_snd_3.dutycount));
	save_item(NAME(m_snd_3.ply_step));
	save_item(NAME(m_snd_3.ply_value));
	// sound 4
	save_item(NAME(m_snd_4.on));
	save_item(NAME(m_snd_4.channel));
	save_item(NAME(m_snd_4.length));
	save_item(NAME(m_snd_4.pos));
	save_item(NAME(m_snd_4.period));
	save_item(NAME(m_snd_4.count));
	save_item(NAME(m_snd_4.mode));
	save_item(NAME(m_snd_4.duty));
	save_item(NAME(m_snd_4.env_value));
	save_item(NAME(m_snd_4.env_direction));
	save_item(NAME(m_snd_4.env_length));
	save_item(NAME(m_snd_4.env_count));
	save_item(NAME(m_snd_4.signal));
	save_item(NAME(m_snd_4.frequency));
	save_item(NAME(m_snd_4.swp_shift));
	save_item(NAME(m_snd_4.swp_direction));
	save_item(NAME(m_snd_4.swp_time));
	save_item(NAME(m_snd_4.swp_count));
	save_item(NAME(m_snd_4.level));
	save_item(NAME(m_snd_4.offset));
	save_item(NAME(m_snd_4.dutycount));
	save_item(NAME(m_snd_4.ply_step));
	save_item(NAME(m_snd_4.ply_value));
}

//-------------------------------------------------
//  device_reset
//-------------------------------------------------

void gameboy_sound_device::device_reset()
{
	memset(&m_snd_1, 0, sizeof(m_snd_1));
	memset(&m_snd_2, 0, sizeof(m_snd_2));
	memset(&m_snd_3, 0, sizeof(m_snd_3));
	memset(&m_snd_4, 0, sizeof(m_snd_4));

	/* Calculate the envelope and sweep tables */
	for (int i = 0; i < 8; i++)
	{
		m_env_length_table[i] = (i * ((1 << FIXED_POINT) / 64) * m_rate) >> FIXED_POINT;
		m_swp_time_table[i] = (((i << FIXED_POINT) / 128) * m_rate) >> (FIXED_POINT - 1);
	}

	/* Calculate the period tables */
	for (int i = 0; i < MAX_FREQUENCIES; i++)
	{
		m_period_table[i] = ((1 << FIXED_POINT) / (131072 / (2048 - i))) * m_rate;
		m_period_mode3_table[i] = ((1 << FIXED_POINT) / (65536 / (2048 - i))) * m_rate;
	}
	/* Calculate the period table for mode 4 */
	for (int i = 0; i < 8; i++)
	{
		for (int j = 0; j < 16; j++)
		{
			// i is the dividing ratio of frequencies
			// j is the shift clock frequency
			m_period_mode4_table[i][j] = ((1 << FIXED_POINT) / (524288 / ((i == 0) ? 0.5 : i) / (1 << (j + 1)))) * m_rate;
		}
	}

	/* Calculate the length table */
	for (int i = 0; i < 64; i++)
		m_length_table[i] = ((64 - i) * ((1 << FIXED_POINT)/256) * m_rate) >> FIXED_POINT;

	/* Calculate the length table for mode 3 */
	for (int i = 0; i < 256; i++)
		m_length_mode3_table[i] = ((256 - i) * ((1 << FIXED_POINT)/256) * m_rate) >> FIXED_POINT;

	sound_w_internal(NR52, 0x00);
	m_snd_regs[AUD3W0] = 0xac;
	m_snd_regs[AUD3W1] = 0xdd;
	m_snd_regs[AUD3W2] = 0xda;
	m_snd_regs[AUD3W3] = 0x48;
	m_snd_regs[AUD3W4] = 0x36;
	m_snd_regs[AUD3W5] = 0x02;
	m_snd_regs[AUD3W6] = 0xcf;
	m_snd_regs[AUD3W7] = 0x16;
	m_snd_regs[AUD3W8] = 0x2c;
	m_snd_regs[AUD3W9] = 0x04;
	m_snd_regs[AUD3WA] = 0xe5;
	m_snd_regs[AUD3WB] = 0x2c;
	m_snd_regs[AUD3WC] = 0xac;
	m_snd_regs[AUD3WD] = 0xdd;
	m_snd_regs[AUD3WE] = 0xda;
	m_snd_regs[AUD3WF] = 0x48;
}


/***************************************************************************
    IMPLEMENTATION
***************************************************************************/

READ8_MEMBER( gameboy_sound_device::wave_r )
{
	/* TODO: properly emulate scrambling of wave ram area when playback is active */
	return m_snd_regs[AUD3W0 + offset] | m_snd_3.on;
}

READ8_MEMBER( gameboy_sound_device::sound_r )
{
	switch (offset)
	{
		case 0x05:
		case 0x0f:
			return 0xff;
		case NR52:
			return 0x70 | m_snd_regs[offset];
		default:
			return m_snd_regs[offset];
	}
}

WRITE8_MEMBER( gameboy_sound_device::wave_w )
{
	m_snd_regs[AUD3W0 + offset] = data;
}

WRITE8_MEMBER( gameboy_sound_device::sound_w )
{
	/* change in registers so update first */
	m_channel->update();

	/* Only register NR52 is accessible if the sound controller is disabled */
	if (!m_snd_control.on && offset != NR52)
		return;

	sound_w_internal(offset, data);
}


void gameboy_sound_device::sound_w_internal( int offset, UINT8 data )
{
	/* Store the value */
	m_snd_regs[offset] = data;

	switch (offset)
	{
	/*MODE 1 */
	case NR10: /* Sweep (R/W) */
		m_snd_1.swp_shift = data & 0x7;
		m_snd_1.swp_direction = (data & 0x8) >> 3;
		m_snd_1.swp_direction |= m_snd_1.swp_direction - 1;
		m_snd_1.swp_time = m_swp_time_table[ (data & 0x70) >> 4 ];
		break;
	case NR11: /* Sound length/Wave pattern duty (R/W) */
		m_snd_1.duty = (data & 0xc0) >> 6;
		m_snd_1.length = m_length_table[data & 0x3f];
		break;
	case NR12: /* Envelope (R/W) */
		m_snd_1.env_value = data >> 4;
		m_snd_1.env_direction = (data & 0x8) >> 3;
		m_snd_1.env_direction |= m_snd_1.env_direction - 1;
		m_snd_1.env_length = m_env_length_table[data & 0x7];
		break;
	case NR13: /* Frequency lo (R/W) */
		m_snd_1.frequency = ((m_snd_regs[NR14] & 0x7) << 8) | m_snd_regs[NR13];
		m_snd_1.period = m_period_table[m_snd_1.frequency];
		break;
	case NR14: /* Frequency hi / Initialize (R/W) */
		m_snd_1.mode = (data & 0x40) >> 6;
		m_snd_1.frequency = ((m_snd_regs[NR14] & 0x7) << 8) | m_snd_regs[NR13];
		m_snd_1.period = m_period_table[m_snd_1.frequency];
		if (data & 0x80)
		{
			if (!m_snd_1.on)
				m_snd_1.pos = 0;
			m_snd_1.on = 1;
			m_snd_1.count = 0;
			m_snd_1.env_value = m_snd_regs[NR12] >> 4;
			m_snd_1.env_count = 0;
			m_snd_1.swp_count = 0;
			m_snd_1.signal = 0x1;
			m_snd_regs[NR52] |= 0x1;
		}
		break;

	/*MODE 2 */
	case NR21: /* Sound length/Wave pattern duty (R/W) */
		m_snd_2.duty = (data & 0xc0) >> 6;
		m_snd_2.length = m_length_table[data & 0x3f];
		break;
	case NR22: /* Envelope (R/W) */
		m_snd_2.env_value = data >> 4;
		m_snd_2.env_direction = (data & 0x8) >> 3;
		m_snd_2.env_direction |= m_snd_2.env_direction - 1;
		m_snd_2.env_length = m_env_length_table[data & 0x7];
		break;
	case NR23: /* Frequency lo (R/W) */
		m_snd_2.period = m_period_table[((m_snd_regs[NR24] & 0x7) << 8) | m_snd_regs[NR23]];
		break;
	case NR24: /* Frequency hi / Initialize (R/W) */
		m_snd_2.mode = (data & 0x40) >> 6;
		m_snd_2.period = m_period_table[((m_snd_regs[NR24] & 0x7) << 8) | m_snd_regs[NR23]];
		if (data & 0x80)
		{
			if (!m_snd_2.on)
				m_snd_2.pos = 0;
			m_snd_2.on = 1;
			m_snd_2.count = 0;
			m_snd_2.env_value = m_snd_regs[NR22] >> 4;
			m_snd_2.env_count = 0;
			m_snd_2.signal = 0x1;
			m_snd_regs[NR52] |= 0x2;
		}
		break;

	/*MODE 3 */
	case NR30: /* Sound On/Off (R/W) */
		m_snd_3.on = (data & 0x80) >> 7;
		break;
	case NR31: /* Sound Length (R/W) */
		m_snd_3.length = m_length_mode3_table[data];
		break;
	case NR32: /* Select Output Level */
		m_snd_3.level = (data & 0x60) >> 5;
		break;
	case NR33: /* Frequency lo (W) */
		m_snd_3.period = m_period_mode3_table[((m_snd_regs[NR34] & 0x7) << 8) + m_snd_regs[NR33]];
		break;
	case NR34: /* Frequency hi / Initialize (W) */
		m_snd_3.mode = (data & 0x40) >> 6;
		m_snd_3.period = m_period_mode3_table[((m_snd_regs[NR34] & 0x7) << 8) + m_snd_regs[NR33]];
		if (data & 0x80)
		{
			if (!m_snd_3.on)
			{
				m_snd_3.pos = 0;
				m_snd_3.offset = 0;
				m_snd_3.duty = 0;
			}
			m_snd_3.on = 1;
			m_snd_3.count = 0;
			m_snd_3.duty = 1;
			m_snd_3.dutycount = 0;
			m_snd_regs[NR52] |= 0x4;
		}
		break;

	/*MODE 4 */
	case NR41: /* Sound Length (R/W) */
		m_snd_4.length = m_length_table[data & 0x3f];
		break;
	case NR42: /* Envelope (R/W) */
		m_snd_4.env_value = data >> 4;
		m_snd_4.env_direction = (data & 0x8) >> 3;
		m_snd_4.env_direction |= m_snd_4.env_direction - 1;
		m_snd_4.env_length = m_env_length_table[data & 0x7];
		break;
	case NR43: /* Polynomial Counter/Frequency */
		m_snd_4.period = m_period_mode4_table[data & 0x7][(data & 0xF0) >> 4];
		m_snd_4.ply_step = (data & 0x8) >> 3;
		break;
	case NR44: /* Counter/Consecutive / Initialize (R/W)  */
		m_snd_4.mode = (data & 0x40) >> 6;
		if (data & 0x80)
		{
			if (!m_snd_4.on)
				m_snd_4.pos = 0;
			m_snd_4.on = 1;
			m_snd_4.count = 0;
			m_snd_4.env_value = m_snd_regs[NR42] >> 4;
			m_snd_4.env_count = 0;
			m_snd_4.signal = machine().rand();
			m_snd_4.ply_value = 0x7fff;
			m_snd_regs[NR52] |= 0x8;
		}
		break;

	/* CONTROL */
	case NR50: /* Channel Control / On/Off / Volume (R/W)  */
		m_snd_control.vol_left = data & 0x7;
		m_snd_control.vol_right = (data & 0x70) >> 4;
		break;
	case NR51: /* Selection of Sound Output Terminal */
		m_snd_control.mode1_right = data & 0x1;
		m_snd_control.mode1_left = (data & 0x10) >> 4;
		m_snd_control.mode2_right = (data & 0x2) >> 1;
		m_snd_control.mode2_left = (data & 0x20) >> 5;
		m_snd_control.mode3_right = (data & 0x4) >> 2;
		m_snd_control.mode3_left = (data & 0x40) >> 6;
		m_snd_control.mode4_right = (data & 0x8) >> 3;
		m_snd_control.mode4_left = (data & 0x80) >> 7;
		break;
	case NR52: /* Sound On/Off (R/W) */
		/* Only bit 7 is writable, writing to bits 0-3 does NOT enable or
		   disable sound.  They are read-only */
		m_snd_control.on = (data & 0x80) >> 7;
		if (!m_snd_control.on)
		{
			sound_w_internal(NR10, 0x80);
			sound_w_internal(NR11, 0x3F);
			sound_w_internal(NR12, 0x00);
			sound_w_internal(NR13, 0xFE);
			sound_w_internal(NR14, 0xBF);
//          sound_w_internal(NR20, 0xFF);
			sound_w_internal(NR21, 0x3F);
			sound_w_internal(NR22, 0x00);
			sound_w_internal(NR23, 0xFF);
			sound_w_internal(NR24, 0xBF);
			sound_w_internal(NR30, 0x7F);
			sound_w_internal(NR31, 0xFF);
			sound_w_internal(NR32, 0x9F);
			sound_w_internal(NR33, 0xFF);
			sound_w_internal(NR34, 0xBF);
//          sound_w_internal(NR40, 0xFF);
			sound_w_internal(NR41, 0xFF);
			sound_w_internal(NR42, 0x00);
			sound_w_internal(NR43, 0x00);
			sound_w_internal(NR44, 0xBF);
			sound_w_internal(NR50, 0x00);
			sound_w_internal(NR51, 0x00);
			m_snd_1.on = 0;
			m_snd_2.on = 0;
			m_snd_3.on = 0;
			m_snd_4.on = 0;
			m_snd_regs[offset] = 0;
		}
		break;
	}
}


//-------------------------------------------------
//  sound_stream_update - handle a stream update
//-------------------------------------------------

void gameboy_sound_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
	stream_sample_t sample, left, right, mode4_mask;

	while (samples-- > 0)
	{
		left = right = 0;

		/* Mode 1 - Wave with Envelope and Sweep */
		if (m_snd_1.on)
		{
			sample = m_snd_1.signal * m_snd_1.env_value;
			m_snd_1.pos++;
			if (m_snd_1.pos == (UINT32)(m_snd_1.period / wave_duty_table[m_snd_1.duty]) >> FIXED_POINT)
			{
				m_snd_1.signal = -m_snd_1.signal;
			}
			else if (m_snd_1.pos > (m_snd_1.period >> FIXED_POINT))
			{
				m_snd_1.pos = 0;
				m_snd_1.signal = -m_snd_1.signal;
			}

			if (m_snd_1.length && m_snd_1.mode)
			{
				m_snd_1.count++;
				if (m_snd_1.count >= m_snd_1.length)
				{
					m_snd_1.on = 0;
					m_snd_regs[NR52] &= 0xFE;
				}
			}

			if (m_snd_1.env_length)
			{
				m_snd_1.env_count++;
				if (m_snd_1.env_count >= m_snd_1.env_length)
				{
					m_snd_1.env_count = 0;
					m_snd_1.env_value += m_snd_1.env_direction;
					if (m_snd_1.env_value < 0)
						m_snd_1.env_value = 0;
					if (m_snd_1.env_value > 15)
						m_snd_1.env_value = 15;
				}
			}

			if (m_snd_1.swp_time)
			{
				m_snd_1.swp_count++;
				if (m_snd_1.swp_count >= m_snd_1.swp_time)
				{
					m_snd_1.swp_count = 0;
					if (m_snd_1.swp_direction > 0)
					{
						m_snd_1.frequency -= m_snd_1.frequency / (1 << m_snd_1.swp_shift);
						if (m_snd_1.frequency <= 0)
						{
							m_snd_1.on = 0;
							m_snd_regs[NR52] &= 0xFE;
						}
					}
					else
					{
						m_snd_1.frequency += m_snd_1.frequency / (1 << m_snd_1.swp_shift);
						if (m_snd_1.frequency >= MAX_FREQUENCIES)
						{
							m_snd_1.frequency = MAX_FREQUENCIES - 1;
						}
					}

					m_snd_1.period = m_period_table[m_snd_1.frequency];
				}
			}

			if (m_snd_control.mode1_left)
				left += sample;
			if (m_snd_control.mode1_right)
				right += sample;
		}

		/* Mode 2 - Wave with Envelope */
		if (m_snd_2.on)
		{
			sample = m_snd_2.signal * m_snd_2.env_value;
			m_snd_2.pos++;
			if( m_snd_2.pos == (UINT32)(m_snd_2.period / wave_duty_table[m_snd_2.duty]) >> FIXED_POINT)
			{
				m_snd_2.signal = -m_snd_2.signal;
			}
			else if (m_snd_2.pos > (m_snd_2.period >> FIXED_POINT))
			{
				m_snd_2.pos = 0;
				m_snd_2.signal = -m_snd_2.signal;
			}

			if (m_snd_2.length && m_snd_2.mode)
			{
				m_snd_2.count++;
				if (m_snd_2.count >= m_snd_2.length)
				{
					m_snd_2.on = 0;
					m_snd_regs[NR52] &= 0xFD;
				}
			}

			if (m_snd_2.env_length)
			{
				m_snd_2.env_count++;
				if (m_snd_2.env_count >= m_snd_2.env_length)
				{
					m_snd_2.env_count = 0;
					m_snd_2.env_value += m_snd_2.env_direction;
					if (m_snd_2.env_value < 0)
						m_snd_2.env_value = 0;
					if (m_snd_2.env_value > 15)
						m_snd_2.env_value = 15;
				}
			}

			if (m_snd_control.mode2_left)
				left += sample;
			if (m_snd_control.mode2_right)
				right += sample;
		}

		/* Mode 3 - Wave patterns from WaveRAM */
		if (m_snd_3.on)
		{
			/* NOTE: This is extremely close, but not quite right.
			 The problem is for GB frequencies above 2000 the frequency gets
			 clipped. This is caused because m_snd_3.pos is never 0 at the test.*/
			sample = m_snd_regs[AUD3W0 + (m_snd_3.offset/2)];
			if (!(m_snd_3.offset % 2))
			{
				sample >>= 4;
			}
			sample = (sample & 0xF) - 8;

			if (m_snd_3.level)
				sample >>= (m_snd_3.level - 1);
			else
				sample = 0;

			m_snd_3.pos++;
			if (m_snd_3.pos >= ((UINT32)(((m_snd_3.period) >> 21)) + m_snd_3.duty))
			{
				m_snd_3.pos = 0;
				if (m_snd_3.dutycount == ((UINT32)(((m_snd_3.period) >> FIXED_POINT)) % 32))
				{
					m_snd_3.duty--;
				}
				m_snd_3.dutycount++;
				m_snd_3.offset++;
				if (m_snd_3.offset > 31)
				{
					m_snd_3.offset = 0;
					m_snd_3.duty = 1;
					m_snd_3.dutycount = 0;
				}
			}

			if (m_snd_3.length && m_snd_3.mode)
			{
				m_snd_3.count++;
				if (m_snd_3.count >= m_snd_3.length)
				{
					m_snd_3.on = 0;
					m_snd_regs[NR52] &= 0xFB;
				}
			}

			if (m_snd_control.mode3_left)
				left += sample;
			if (m_snd_control.mode3_right)
				right += sample;
		}

		/* Mode 4 - Noise with Envelope */
		if (m_snd_4.on)
		{
			/* Similar problem to Mode 3, we seem to miss some notes */
			sample = m_snd_4.signal & m_snd_4.env_value;
			m_snd_4.pos++;
			if (m_snd_4.pos == (m_snd_4.period >> (FIXED_POINT + 1)))
			{
				/* Using a Polynomial Counter (aka Linear Feedback Shift Register)
				 Mode 4 has a 7 bit and 15 bit counter so we need to shift the
				 bits around accordingly */
				mode4_mask = (((m_snd_4.ply_value & 0x2) >> 1) ^ (m_snd_4.ply_value & 0x1)) << (m_snd_4.ply_step ? 6 : 14);
				m_snd_4.ply_value >>= 1;
				m_snd_4.ply_value |= mode4_mask;
				m_snd_4.ply_value &= (m_snd_4.ply_step ? 0x7f : 0x7fff);
				m_snd_4.signal = (INT8)m_snd_4.ply_value;
			}
			else if (m_snd_4.pos > (m_snd_4.period >> FIXED_POINT))
			{
				m_snd_4.pos = 0;
				mode4_mask = (((m_snd_4.ply_value & 0x2) >> 1) ^ (m_snd_4.ply_value & 0x1)) << (m_snd_4.ply_step ? 6 : 14);
				m_snd_4.ply_value >>= 1;
				m_snd_4.ply_value |= mode4_mask;
				m_snd_4.ply_value &= (m_snd_4.ply_step ? 0x7f : 0x7fff);
				m_snd_4.signal = (INT8)m_snd_4.ply_value;
			}

			if (m_snd_4.length && m_snd_4.mode)
			{
				m_snd_4.count++;
				if (m_snd_4.count >= m_snd_4.length)
				{
					m_snd_4.on = 0;
					m_snd_regs[NR52] &= 0xF7;
				}
			}

			if (m_snd_4.env_length)
			{
				m_snd_4.env_count++;
				if (m_snd_4.env_count >= m_snd_4.env_length)
				{
					m_snd_4.env_count = 0;
					m_snd_4.env_value += m_snd_4.env_direction;
					if (m_snd_4.env_value < 0)
						m_snd_4.env_value = 0;
					if (m_snd_4.env_value > 15)
						m_snd_4.env_value = 15;
				}
			}

			if (m_snd_control.mode4_left)
				left += sample;
			if (m_snd_control.mode4_right)
				right += sample;
		}

		/* Adjust for master volume */
		left *= m_snd_control.vol_left;
		right *= m_snd_control.vol_right;

		/* pump up the volume */
		left <<= 6;
		right <<= 6;

		/* Update the buffers */
		*(outputs[0]++) = left;
		*(outputs[1]++) = right;
	}

	m_snd_regs[NR52] = (m_snd_regs[NR52]&0xf0) | m_snd_1.on | (m_snd_2.on << 1) | (m_snd_3.on << 2) | (m_snd_4.on << 3);

}