summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/drivers/xerox820.cpp
blob: f0ce88ec8d0ca370a5ae63b7a1ef8f78a3693d36 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
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
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
// license:BSD-3-Clause
// copyright-holders:Curt Coder
/***************************************************************************

        Xerox 820

        12/05/2009 Skeleton driver.

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

/*

    TODO:

    - Xerox 820
        - floppy format has 3xcd at the end of track data
            :u109: write track 0
            :u109: track description 16xff ... 109xff 3xcd
    - Xerox 820-II
        - floppy (read/write to FDC triggers Z80 WAIT)
        - Winchester
            - Shugart SA1004 (chs=256,4,40 ss=256)
            - Shugart SA606 (chs=160,6, ss=256)
            - Shugart SA1403D controller
    - Xerox 16/8
    - Emerald Microware X120 board
    - type in Monitor v1.0 from manual
    - ASCII keyboard
    - low-profile keyboard

    http://www.vintagesbc.it/?page_id=233
    http://mccworkshop.com/computers/comphistory7.htm
    http://bitsavers.org/bits/Xerox/820/
    http://bitsavers.org/bits/Xerox/820-II/
    http://www.classiccmp.org/dunfield/img54306/system.htm

    Note:
    - MK-82 have same roms as original Big Board
    - MK-83 have 256K of RAM

    8-inch formats
    77 tracks, 1 head, 26 sectors, 128 bytes sector length, first sector id 1
    77 tracks, 1 head, 26 sectors, 256 bytes sector length, first sector id 1

    5.25-inch formats
    40 tracks, 1 head, 18 sectors, 128 bytes sector length, first sector id 1
    40 tracks, 2 heads, 18 sectors, 128 bytes sector length, first sector id 1

    SmartROM and Plus2 ROM both come for 2.5MHz or 4MHz systems, and there is another distinction between variants for generic or Xerox keyboards
    http://www.microcodeconsulting.com/z80/plus2.htm
    http://www.microcodeconsulting.com/z80/smartrom.htm

*/


#include "emu.h"
#include "includes/xerox820.h"

#include "screen.h"
#include "softlist.h"
#include "speaker.h"


/* Read/Write Handlers */

void xerox820_state::bankswitch(int bank)
{
	address_space &program = m_maincpu->space(AS_PROGRAM);
	uint8_t *ram = m_ram->pointer();

	if (bank)
	{
		/* ROM */
		program.install_rom(0x0000, 0x0fff, m_rom->base());
		program.unmap_readwrite(0x1000, 0x1fff);
		program.install_ram(0x3000, 0x3fff, m_video_ram);
	}
	else
	{
		/* RAM */
		program.install_ram(0x0000, 0x3fff, ram);
	}
}

void xerox820ii_state::bankswitch(int bank)
{
	address_space &program = m_maincpu->space(AS_PROGRAM);
	uint8_t *ram = m_ram->pointer();

	if (bank)
	{
		/* ROM */
		program.install_rom(0x0000, 0x1fff, m_rom->base());
		program.unmap_readwrite(0x2000, 0x2fff);
		program.install_ram(0x3000, 0x3fff, m_video_ram);
		program.unmap_readwrite(0x4000, 0xbfff);
	}
	else
	{
		/* RAM */
		program.install_ram(0x0000, 0xbfff, ram);
	}
}

READ8_MEMBER( xerox820_state::fdc_r )
{
	return m_fdc->read(offset) ^ 0xff;
}

WRITE8_MEMBER( xerox820_state::fdc_w )
{
	m_fdc->write(offset, data ^ 0xff);
}

WRITE8_MEMBER( xerox820_state::scroll_w )
{
	m_scroll = (offset >> 8) & 0x1f;
}

#ifdef UNUSED_CODE
WRITE8_MEMBER( xerox820_state::x120_system_w )
{
	/*

	    bit     signal      description

	    0       DSEL0       drive select bit 0 (01=A, 10=B, 00=C, 11=D)
	    1       DSEL1       drive select bit 1
	    2       SIDE        side select
	    3       VATT        video attribute (0=inverse, 1=blinking)
	    4       BELL        bell trigger
	    5       DENSITY     density (0=double, 1=single)
	    6       _MOTOR      disk motor (0=on, 1=off)
	    7       BANK        memory bank switch (0=RAM, 1=ROM/video)

	*/
}
#endif

WRITE8_MEMBER( xerox820ii_state::bell_w )
{
	m_speaker->level_w(offset);
}

WRITE8_MEMBER( xerox820ii_state::slden_w )
{
	m_fdc->dden_w(offset);
}

WRITE8_MEMBER( xerox820ii_state::chrom_w )
{
	m_chrom = offset;
}

WRITE8_MEMBER( xerox820ii_state::lowlite_w )
{
	m_lowlite = data;
}

WRITE8_MEMBER( xerox820ii_state::sync_w )
{
	if (offset)
	{
		/* set external clocks for synchronous sio A */
	}
	else
	{
		/* set internal clocks for asynchronous sio A */
	}
}

/* Memory Maps */

void xerox820_state::xerox820_mem(address_map &map)
{
	map.unmap_value_high();
	map(0x3000, 0x3fff).ram().share("video_ram");
	map(0x4000, 0xffff).ram();
}

void xerox820_state::xerox820_io(address_map &map)
{
	map(0x00, 0x00).mirror(0xff03).w(COM8116_TAG, FUNC(com8116_device::str_w));
	map(0x04, 0x07).mirror(0xff00).rw(m_sio, FUNC(z80sio0_device::ba_cd_r), FUNC(z80sio0_device::ba_cd_w));
	map(0x08, 0x0b).mirror(0xff00).rw(Z80PIO_GP_TAG, FUNC(z80pio_device::read_alt), FUNC(z80pio_device::write_alt));
	map(0x0c, 0x0c).mirror(0xff03).w(COM8116_TAG, FUNC(com8116_device::stt_w));
	map(0x10, 0x13).mirror(0xff00).rw(FUNC(xerox820_state::fdc_r), FUNC(xerox820_state::fdc_w));
	map(0x14, 0x14).mirror(0x0003).select(0xff00).w(FUNC(xerox820_state::scroll_w));
	map(0x18, 0x1b).mirror(0xff00).rw(m_ctc, FUNC(z80ctc_device::read), FUNC(z80ctc_device::write));
	map(0x1c, 0x1f).mirror(0xff00).rw(m_kbpio, FUNC(z80pio_device::read_alt), FUNC(z80pio_device::write_alt));
}

void xerox820ii_state::xerox820ii_mem(address_map &map)
{
	map.unmap_value_high();
	map(0x3000, 0x3fff).ram().share("video_ram");
	map(0xc000, 0xffff).ram();
}

void xerox820ii_state::xerox820ii_io(address_map &map)
{
	xerox820_io(map);
	map(0x28, 0x29).mirror(0xff00).w(FUNC(xerox820ii_state::bell_w));
	map(0x30, 0x31).mirror(0xff00).w(FUNC(xerox820ii_state::slden_w));
	map(0x34, 0x35).mirror(0xff00).w(FUNC(xerox820ii_state::chrom_w));
	map(0x36, 0x36).mirror(0xff00).w(FUNC(xerox820ii_state::lowlite_w));
	map(0x68, 0x69).mirror(0xff00).w(FUNC(xerox820ii_state::sync_w));
}

void xerox820ii_state::xerox168_mem(address_map &map)
{
	map(0x00000, 0x3ffff).ram();
	map(0xff000, 0xfffff).rom().region(I8086_TAG, 0);
}

void xerox820_state::mk83_mem(address_map &map)
{
	map.unmap_value_high();
	map(0x3000, 0x6fff).ram();
	map(0x7000, 0x7fff).ram().share("video_ram");
	map(0x8000, 0xffff).ram();
}


/* Input Ports */

static INPUT_PORTS_START( xerox820 )
	// inputs defined in machine/keyboard.c
INPUT_PORTS_END

TIMER_CALLBACK_MEMBER( bigboard_state::bigboard_beepoff )
{
	m_beeper->set_state(0);
}

/* Z80 PIO */

READ8_MEMBER( xerox820_state::kbpio_pa_r )
{
	/*

	    bit     signal          description

	    0
	    1
	    2
	    3       PBRDY           keyboard data available
	    4       8/N5            8"/5.25" disk select (0=5.25", 1=8")
	    5       400/460         double sided disk detect (only on Etch 2 PCB) (0=SS, 1=DS)
	    6
	    7

	*/

	uint8_t data = 0;

	// keyboard
	data |= m_kbpio->rdy_b() << 3;

	// floppy
	data |= m_8n5 << 4;
	data |= m_400_460 << 5;

	return data;
}

WRITE8_MEMBER( xerox820_state::kbpio_pa_w )
{
	/*

	    bit     signal          description

	    0       _DVSEL1         drive select 1
	    1       _DVSEL2         drive select 2
	    2       SIDE            side select
	    3
	    4
	    5
	    6       NCSET2          display character set (inverted and connected to chargen A10)
	    7       BANK            bank switching (0=RAM, 1=ROM/videoram)

	*/

	/* drive select */
	floppy_image_device *floppy = nullptr;

	if (BIT(data, 0)) floppy = m_floppy0->get_device();
	if (BIT(data, 1)) floppy = m_floppy1->get_device();

	m_fdc->set_floppy(floppy);

	if (floppy)
	{
		int _8n5 = (floppy->get_form_factor() == floppy_image::FF_8);

		if (m_8n5 != _8n5)
		{
			m_8n5 = _8n5;

			m_fdc->set_unscaled_clock(m_8n5 ? 20_MHz_XTAL / 10 : 20_MHz_XTAL / 20);
		}

		m_400_460 = !floppy->twosid_r();

		floppy->mon_w(0);

		floppy->ss_w(BIT(data, 2));
	}

	/* display character set */
	m_ncset2 = !BIT(data, 6);

	/* bank switching */
	bankswitch(BIT(data, 7));
}

WRITE8_MEMBER( bigboard_state::kbpio_pa_w )
{
	xerox820_state::kbpio_pa_w(space, offset, data);

	/* beeper on bigboard */
	if (BIT(data, 5) & (!m_bit5))
	{
		machine().scheduler().timer_set(attotime::from_msec(40), timer_expired_delegate(FUNC(bigboard_state::bigboard_beepoff),this));
		m_beeper->set_state(1);
	}
	m_bit5 = BIT(data, 5);
}

READ8_MEMBER( xerox820_state::kbpio_pb_r )
{
	/*

	    bit     description

	    0       KB0
	    1       KB1
	    2       KB2
	    3       KB3
	    4       KB4
	    5       KB5
	    6       KB6
	    7       KB7

	*/

	return m_kb->read() ^ 0xff;
}

WRITE8_MEMBER( xerox820ii_state::rdpio_pb_w )
{
	/*

	    bit     description

	    0       NBSY
	    1       NMSG
	    2       NC/D
	    3       NREQ
	    4       NI/O
	    5       NSEL
	    6       LS74 Q
	    7       NRST
	*/

	m_sasibus->write_sel(!BIT(data, 5));
	m_sasibus->write_rst(!BIT(data, 7));
	// TODO: LS74 Q
}

WRITE_LINE_MEMBER( xerox820ii_state::rdpio_pardy_w )
{
	// TODO
}

/* Z80 CTC */

TIMER_DEVICE_CALLBACK_MEMBER( xerox820_state::ctc_tick )
{
	m_ctc->trg0(1);
	m_ctc->trg0(0);
}

/* Z80 Daisy Chain */

static const z80_daisy_config xerox820_daisy_chain[] =
{
	{ Z80SIO_TAG },
	{ Z80PIO_KB_TAG },
	{ Z80PIO_GP_TAG },
	{ Z80CTC_TAG },
	{ nullptr }
};



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

    Quickload

    This loads a .COM file to address 0x100 then jumps
    there. Sometimes .COM has been renamed to .CPM to
    prevent windows going ballistic. These can be loaded
    as well.

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

QUICKLOAD_LOAD_MEMBER( xerox820_state, xerox820 )
{
	address_space& prog_space = m_maincpu->space(AS_PROGRAM);

	if (quickload_size >= 0xfd00)
		return image_init_result::FAIL;

	bankswitch(0);

	/* Avoid loading a program if CP/M-80 is not in memory */
	if ((prog_space.read_byte(0) != 0xc3) || (prog_space.read_byte(5) != 0xc3))
	{
		machine_reset();
		return image_init_result::FAIL;
	}

	/* Load image to the TPA (Transient Program Area) */
	for (uint16_t i = 0; i < quickload_size; i++)
	{
		uint8_t data;
		if (image.fread( &data, 1) != 1)
			return image_init_result::FAIL;
		prog_space.write_byte(i+0x100, data);
	}

	/* clear out command tail */
	prog_space.write_byte(0x80, 0);   prog_space.write_byte(0x81, 0);

	/* Roughly set SP basing on the BDOS position */
	m_maincpu->set_state_int(Z80_SP, 256 * prog_space.read_byte(7) - 300);
	m_maincpu->set_pc(0x100);   // start program

	return image_init_result::PASS;
}



/* WD1771 Interface */

static void xerox820_floppies(device_slot_interface &device)
{
	device.option_add("sa400", FLOPPY_525_SSSD_35T); // Shugart SA-400, 35 trk drive
	device.option_add("sa400l", FLOPPY_525_SSSD); // Shugart SA-400, 40 trk drive
	device.option_add("sa450", FLOPPY_525_DD); // Shugart SA-450
	device.option_add("sa800", FLOPPY_8_SSDD); // Shugart SA-800
	device.option_add("sa850", FLOPPY_8_DSDD); // Shugart SA-850
}

void xerox820_state::update_nmi()
{
	int halt = m_maincpu->state_int(Z80_HALT);
	int state = (halt && (m_fdc_irq || m_fdc_drq)) ? ASSERT_LINE : CLEAR_LINE;

	m_maincpu->set_input_line(INPUT_LINE_NMI, state);
}

WRITE_LINE_MEMBER( xerox820_state::fdc_intrq_w )
{
	m_fdc_irq = state;

	update_nmi();
}

WRITE_LINE_MEMBER( xerox820_state::fdc_drq_w )
{
	m_fdc_drq = state;

	update_nmi();
}

/* Video */

uint32_t xerox820_state::screen_update(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
{
	uint8_t y,ra,chr,gfx;
	uint16_t sy=0,ma=(m_scroll + 1) * 0x80,x;
	const pen_t *pen=m_palette->pens();

	m_framecnt++;

	for (y = 0; y < 24; y++)
	{
		if (ma > 0xb80) ma = 0;

		for (ra = 0; ra < 10; ra++)
		{
			uint32_t *p = &bitmap.pix32(sy++);

			for (x = ma; x < ma + 80; x++)
			{
				if (ra < 8)
				{
					chr = m_video_ram[x & XEROX820_VIDEORAM_MASK] ^ 0x80;

					/* Take care of flashing characters */
					if ((chr < 0x80) && (m_framecnt & 0x08))
						chr |= 0x80;

					/* get pattern of pixels for that character scanline */
					gfx = m_char_rom->base()[(m_ncset2 << 10) | (chr<<3) | ra ];
				}
				else
					gfx = 0xff;

			/* Display a scanline of a character (7 pixels) */
			*p++ = pen[0];
			*p++ = pen[BIT(gfx, 4) ^ 1];
			*p++ = pen[BIT(gfx, 3) ^ 1];
			*p++ = pen[BIT(gfx, 2) ^ 1];
			*p++ = pen[BIT(gfx, 1) ^ 1];
			*p++ = pen[BIT(gfx, 0) ^ 1];
			*p++ = pen[0];
			}
		}
		ma+=128;
	}
	return 0;
}

/* Machine Initialization */

void xerox820_state::machine_start()
{
	// state saving
	save_item(NAME(m_scroll));
	save_item(NAME(m_ncset2));
	save_item(NAME(m_vatt));
	save_item(NAME(m_fdc_irq));
	save_item(NAME(m_fdc_drq));
	save_item(NAME(m_8n5));
	save_item(NAME(m_400_460));
}

void xerox820_state::machine_reset()
{
	bankswitch(1);

	m_fdc->reset();
}

void bigboard_state::machine_reset()
{
	bankswitch(1);

	/* bigboard has a one-pulse output to drive a user-supplied beeper */
	m_beeper->set_state(0);

	m_fdc->reset();
}

void xerox820ii_state::machine_reset()
{
	bankswitch(1);

	m_fdc->reset();
}


/* F4 Character Displayer */
static const gfx_layout xerox820_charlayout =
{
	8, 8,                   /* 8 x 8 characters */
	256,                    /* 256 characters */
	1,                  /* 1 bits per pixel */
	{ 0 },                  /* no bitplanes */
	/* x offsets */
	{ 0, 1, 2, 3, 4, 5, 6, 7 },
	/* y offsets */
	{  0*8,  1*8,  2*8,  3*8,  4*8,  5*8,  6*8,  7*8, 8*8,  9*8, 10*8, 11*8, 12*8, 13*8, 14*8, 15*8 },
	8*8                 /* every char takes 8 bytes */
};

static const gfx_layout xerox820_gfxlayout =
{
	8, 8,                   /* 8 x 8 characters */
	256,                    /* 256 characters */
	1,                  /* 1 bits per pixel */
	{ 0 },                  /* no bitplanes */
	/* x offsets */
	{ 0, 1, 2, 3, 4, 5, 6, 7 },
	/* y offsets */
	{  0*8,  1*8,  2*8,  3*8,  4*8,  5*8,  6*8,  7*8, 8*8,  9*8, 10*8, 11*8, 12*8, 13*8, 14*8, 15*8 },
	8*8                 /* every char takes 8 bytes */
};

static GFXDECODE_START( gfx_xerox820 )
	GFXDECODE_ENTRY( "chargen", 0x0000, xerox820_charlayout, 0, 1 )
GFXDECODE_END

static GFXDECODE_START( gfx_xerox820ii )
	GFXDECODE_ENTRY( "chargen", 0x0000, xerox820_charlayout, 0, 1 )
	GFXDECODE_ENTRY( "chargen", 0x0800, xerox820_gfxlayout, 0, 1 )
GFXDECODE_END

/* Machine Drivers */

MACHINE_CONFIG_START(xerox820_state::xerox820)
	/* basic machine hardware */
	Z80(config, m_maincpu, 20_MHz_XTAL / 8);
	m_maincpu->set_addrmap(AS_PROGRAM, &xerox820_state::xerox820_mem);
	m_maincpu->set_addrmap(AS_IO, &xerox820_state::xerox820_io);
	m_maincpu->set_daisy_config(xerox820_daisy_chain);

	/* video hardware */
	MCFG_SCREEN_ADD(SCREEN_TAG, RASTER)
	MCFG_SCREEN_UPDATE_DRIVER(xerox820_state, screen_update)
	MCFG_SCREEN_RAW_PARAMS(10.69425_MHz_XTAL, 700, 0, 560, 260, 0, 240)

	GFXDECODE(config, "gfxdecode", m_palette, gfx_xerox820);
	PALETTE(config, m_palette, palette_device::MONOCHROME);

	/* devices */
	Z80PIO(config, m_kbpio, 20_MHz_XTAL / 8);
	m_kbpio->out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);
	m_kbpio->in_pa_callback().set(FUNC(xerox820_state::kbpio_pa_r));
	m_kbpio->out_pa_callback().set(FUNC(xerox820_state::kbpio_pa_w));
	m_kbpio->in_pb_callback().set(FUNC(xerox820_state::kbpio_pb_r));

	z80pio_device& pio_gp(Z80PIO(config, Z80PIO_GP_TAG, 20_MHz_XTAL / 8));
	pio_gp.out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);

	Z80CTC(config, m_ctc, 20_MHz_XTAL / 8);
	m_ctc->intr_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);
	m_ctc->zc_callback<0>().set(m_ctc, FUNC(z80ctc_device::trg1));
	m_ctc->zc_callback<2>().set(m_ctc, FUNC(z80ctc_device::trg3));
	//TIMER(config, "ctc").configure_periodic(FUNC(xerox820_state::ctc_tick), attotime::from_hz(20_MHz_XTAL / 8));

	FD1771(config, m_fdc, 20_MHz_XTAL / 20);
	m_fdc->intrq_wr_callback().set(FUNC(xerox820_state::fdc_intrq_w));
	m_fdc->drq_wr_callback().set(FUNC(xerox820_state::fdc_drq_w));
	FLOPPY_CONNECTOR(config, FD1771_TAG":0", xerox820_floppies, "sa400l", floppy_image_device::default_floppy_formats);
	FLOPPY_CONNECTOR(config, FD1771_TAG":1", xerox820_floppies, "sa400l", floppy_image_device::default_floppy_formats);

	Z80SIO0(config, m_sio, 20_MHz_XTAL / 8);
	m_sio->out_txda_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_txd));
	m_sio->out_dtra_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_dtr));
	m_sio->out_rtsa_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_rts));
	m_sio->out_txdb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_txd));
	m_sio->out_dtrb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_dtr));
	m_sio->out_rtsb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_rts));
	m_sio->out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);

	rs232_port_device &rs232a(RS232_PORT(config, RS232_A_TAG, default_rs232_devices, nullptr));
	rs232a.rxd_handler().set(m_sio, FUNC(z80sio0_device::rxa_w));

	rs232_port_device &rs232b(RS232_PORT(config, RS232_B_TAG, default_rs232_devices, nullptr));
	rs232b.rxd_handler().set(m_sio, FUNC(z80sio0_device::rxb_w));

	com8116_device &dbrg(COM8116(config, COM8116_TAG, 5.0688_MHz_XTAL));
	dbrg.fr_handler().set(m_sio, FUNC(z80dart_device::rxca_w));
	dbrg.fr_handler().append(m_sio, FUNC(z80dart_device::txca_w));
	dbrg.ft_handler().set(m_sio, FUNC(z80dart_device::rxtxcb_w));

	XEROX_820_KEYBOARD(config, m_kb, 0);
	m_kb->kbstb_wr_callback().set(m_kbpio, FUNC(z80pio_device::strobe_b));

	/* internal ram */
	RAM(config, m_ram).set_default_size("64K");

	// software lists
	SOFTWARE_LIST(config, "flop_list").set_original("xerox820");
	MCFG_QUICKLOAD_ADD("quickload", xerox820_state, xerox820, "com,cpm", attotime::from_seconds(3))
MACHINE_CONFIG_END

MACHINE_CONFIG_START(bigboard_state::bigboard)
	xerox820(config);
	/* sound hardware */
	SPEAKER(config, "mono").front_center();
	MCFG_DEVICE_ADD("beeper", BEEP, 950)
	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.00) /* bigboard only */
MACHINE_CONFIG_END

MACHINE_CONFIG_START(xerox820ii_state::xerox820ii)
	/* basic machine hardware */
	Z80(config, m_maincpu, 16_MHz_XTAL / 4);
	m_maincpu->set_addrmap(AS_PROGRAM, &xerox820ii_state::xerox820ii_mem);
	m_maincpu->set_addrmap(AS_IO, &xerox820ii_state::xerox820ii_io);
	m_maincpu->set_daisy_config(xerox820_daisy_chain);

	/* video hardware */
	MCFG_SCREEN_ADD(SCREEN_TAG, RASTER)
	MCFG_SCREEN_UPDATE_DRIVER(xerox820ii_state, screen_update)
	MCFG_SCREEN_RAW_PARAMS(10.69425_MHz_XTAL, 700, 0, 560, 260, 0, 240)

	GFXDECODE(config, "gfxdecode", m_palette, gfx_xerox820ii);
	PALETTE(config, m_palette, palette_device::MONOCHROME);

	/* sound hardware */
	SPEAKER(config, "mono").front_center();
	MCFG_DEVICE_ADD("speaker", SPEAKER_SOUND)
	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 0.50)

	/* devices */
	Z80PIO(config, m_kbpio, 16_MHz_XTAL / 4);
	m_kbpio->out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);
	m_kbpio->in_pa_callback().set(FUNC(xerox820_state::kbpio_pa_r));
	m_kbpio->out_pa_callback().set(FUNC(xerox820_state::kbpio_pa_w));
	m_kbpio->in_pb_callback().set(FUNC(xerox820_state::kbpio_pb_r));

	z80pio_device& pio_gp(Z80PIO(config, Z80PIO_GP_TAG, 16_MHz_XTAL / 4));
	pio_gp.out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);

	z80pio_device& pio_rd(Z80PIO(config, Z80PIO_RD_TAG, 20_MHz_XTAL / 8));
	pio_rd.out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);
	pio_rd.in_pa_callback().set("sasi_data_in", FUNC(input_buffer_device::bus_r));
	pio_rd.out_pa_callback().set("sasi_data_out", FUNC(output_latch_device::bus_w));
	pio_rd.out_ardy_callback().set(FUNC(xerox820ii_state::rdpio_pardy_w));
	pio_rd.in_pb_callback().set("sasi_ctrl_in", FUNC(input_buffer_device::bus_r));
	pio_rd.out_pb_callback().set(FUNC(xerox820ii_state::rdpio_pb_w));

	Z80CTC(config, m_ctc, 16_MHz_XTAL / 4);
	m_ctc->intr_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);
	m_ctc->zc_callback<0>().set(m_ctc, FUNC(z80ctc_device::trg1));
	m_ctc->zc_callback<2>().set(m_ctc, FUNC(z80ctc_device::trg3));
	//TIMER(config, "ctc").configure_periodic(FUNC(xerox820_state::ctc_tick), attotime::from_hz(16_MHz_XTAL / 4));

	FD1797(config, m_fdc, 16_MHz_XTAL / 8);
	m_fdc->intrq_wr_callback().set(FUNC(xerox820_state::fdc_intrq_w));
	m_fdc->drq_wr_callback().set(FUNC(xerox820_state::fdc_drq_w));
	FLOPPY_CONNECTOR(config, FD1797_TAG":0", xerox820_floppies, "sa450", floppy_image_device::default_floppy_formats);
	FLOPPY_CONNECTOR(config, FD1797_TAG":1", xerox820_floppies, "sa450", floppy_image_device::default_floppy_formats);

	Z80SIO0(config, m_sio, 16_MHz_XTAL / 4);
	m_sio->out_txda_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_txd));
	m_sio->out_dtra_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_dtr));
	m_sio->out_rtsa_callback().set(RS232_A_TAG, FUNC(rs232_port_device::write_rts));
	m_sio->out_txdb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_txd));
	m_sio->out_dtrb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_dtr));
	m_sio->out_rtsb_callback().set(RS232_B_TAG, FUNC(rs232_port_device::write_rts));
	m_sio->out_int_callback().set_inputline(m_maincpu, INPUT_LINE_IRQ0);

	rs232_port_device &rs232a(RS232_PORT(config, RS232_A_TAG, default_rs232_devices, nullptr));
	rs232a.rxd_handler().set(m_sio, FUNC(z80sio0_device::rxa_w));

	rs232_port_device &rs232b(RS232_PORT(config, RS232_B_TAG, default_rs232_devices, nullptr));
	rs232b.rxd_handler().set(m_sio, FUNC(z80sio0_device::rxb_w));

	com8116_device &dbrg(COM8116(config, COM8116_TAG, 5.0688_MHz_XTAL));
	dbrg.fr_handler().set(m_sio, FUNC(z80dart_device::rxca_w));
	dbrg.fr_handler().append(m_sio, FUNC(z80dart_device::txca_w));
	dbrg.ft_handler().set(m_sio, FUNC(z80dart_device::rxtxcb_w));

	XEROX_820_KEYBOARD(config, m_kb, 0);
	m_kb->kbstb_wr_callback().set(m_kbpio, FUNC(z80pio_device::strobe_b));

	// SASI bus
	SCSI_PORT(config, m_sasibus, 0);
	m_sasibus->set_data_input_buffer("sasi_data_in");
	m_sasibus->bsy_handler().set("sasi_ctrl_in", FUNC(input_buffer_device::write_bit0)).exor(1);
	m_sasibus->msg_handler().set("sasi_ctrl_in", FUNC(input_buffer_device::write_bit1)).exor(1);
	m_sasibus->cd_handler().set("sasi_ctrl_in", FUNC(input_buffer_device::write_bit2)).exor(1);
	m_sasibus->req_handler().set("sasi_ctrl_in", FUNC(input_buffer_device::write_bit3)).exor(1);
	m_sasibus->io_handler().set("sasi_ctrl_in", FUNC(input_buffer_device::write_bit4)).exor(1);

	MCFG_SCSIDEV_ADD(SASIBUS_TAG ":" SCSI_PORT_DEVICE1, "harddisk", SA1403D, SCSI_ID_0)

	output_latch_device &sasi_data_out(OUTPUT_LATCH(config, "sasi_data_out"));
	m_sasibus->set_output_latch(sasi_data_out);
	INPUT_BUFFER(config, "sasi_data_in");
	INPUT_BUFFER(config, "sasi_ctrl_in");

	/* internal ram */
	RAM(config, m_ram).set_default_size("64K");

	// software lists
	SOFTWARE_LIST(config, "flop_list").set_original("xerox820ii");
	MCFG_QUICKLOAD_ADD("quickload", xerox820_state, xerox820, "com,cpm", attotime::from_seconds(3))
MACHINE_CONFIG_END

MACHINE_CONFIG_START(xerox820ii_state::xerox168)
	xerox820ii(config);
	MCFG_DEVICE_ADD(I8086_TAG, I8086, 4770000)
	MCFG_DEVICE_PROGRAM_MAP(xerox168_mem)

	/* internal ram */
	m_ram->set_default_size("192K").set_extra_options("320K");
MACHINE_CONFIG_END

void xerox820_state::mk83(machine_config & config)
{
	xerox820(config);

	m_maincpu->set_addrmap(AS_PROGRAM, &xerox820_state::mk83_mem);
}

/* ROMs */

ROM_START( bigboard )
	ROM_REGION( 0x1000, Z80_TAG, 0 )
	ROM_LOAD( "bigboard.u67", 0x0000, 0x0800, CRC(5a85a228) SHA1(d51a2cbd0aae80315bda9530275aabfe8305364e) )

	ROM_REGION( 0x800, "chargen", 0 )
	ROM_LOAD( "bigboard.u73", 0x0000, 0x0800, CRC(10bf0d81) SHA1(7ec73670a4d9d6421a5d6a4c4edc8b7c87923f6c) )
ROM_END

#define rom_mk82 rom_bigboard

ROM_START( x820 )
	ROM_REGION( 0x1000, Z80_TAG, 0 )
	ROM_DEFAULT_BIOS( "v20" )
	ROM_SYSTEM_BIOS( 0, "v10", "Xerox Monitor v1.0" )
	ROMX_LOAD( "x820v10.u64", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(0) )
	ROMX_LOAD( "x820v10.u63", 0x0800, 0x0800, NO_DUMP, ROM_BIOS(0) )
	ROM_SYSTEM_BIOS( 1, "v20", "Xerox Monitor v2.0" )
	ROMX_LOAD( "x820v20.u64", 0x0000, 0x0800, CRC(2fc227e2) SHA1(b4ea0ae23d281a687956e8a514cb364a1372678e), ROM_BIOS(1) )
	ROMX_LOAD( "x820v20.u63", 0x0800, 0x0800, CRC(bc11f834) SHA1(4fd2b209a6e6ff9b0c41800eb5228c34a0d7f7ef), ROM_BIOS(1) )
	ROM_SYSTEM_BIOS( 2, "smart23", "MICROCode SmartROM v2.3" )
	ROMX_LOAD( "mxkx25a.u64", 0x0000, 0x0800, CRC(7ec5f100) SHA1(5d0ff35a51aa18afc0d9c20ef99ff5d9d3f2075b), ROM_BIOS(2) )
	ROMX_LOAD( "mxkx25b.u63", 0x0800, 0x0800, CRC(a7543798) SHA1(886e617e1003d13f86f33085cbd49391b77291a3), ROM_BIOS(2) )
	ROM_SYSTEM_BIOS( 3, "plus2", "MICROCode Plus2 v0.2a" )
	ROMX_LOAD( "p2x25a.u64",  0x0000, 0x0800, CRC(3ccd7a8f) SHA1(6e46c88f03fc7289595dd6bec95e23bb13969525), ROM_BIOS(3) )
	ROMX_LOAD( "p2x25b.u63",  0x0800, 0x0800, CRC(1e580391) SHA1(e91f8ce82586df33c0d6d02eb005e8079f4de67d), ROM_BIOS(3) )

	ROM_REGION( 0x800, "chargen", 0 )
	ROM_LOAD( "x820.u92", 0x0000, 0x0800, CRC(b823fa98) SHA1(ad0ea346aa257a53ad5701f4201896a2b3a0f928) )
ROM_END

ROM_START( x820ii )
	ROM_REGION( 0x2000, Z80_TAG, 0 )
	ROM_DEFAULT_BIOS( "v404" )

	ROM_SYSTEM_BIOS( 0, "v400", "Balcones Operating System v4.00" ) // Initial U.S. 3-ROM set: support for double density disks
	ROMX_LOAD( "v400.u33", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(0) )
	ROMX_LOAD( "v400.u34", 0x0800, 0x0800, NO_DUMP, ROM_BIOS(0) )
	ROMX_LOAD( "v400.u35", 0x1000, 0x0800, NO_DUMP, ROM_BIOS(0) )

	ROM_SYSTEM_BIOS( 1, "v401", "Balcones Operating System v4.01" ) // Corrected overflow problem with large data files
	ROMX_LOAD( "v401.u33", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(1) )
	ROMX_LOAD( "v401.u34", 0x0800, 0x0800, NO_DUMP, ROM_BIOS(1) )
	ROMX_LOAD( "v401.u35", 0x1000, 0x0800, NO_DUMP, ROM_BIOS(1) )

	ROM_SYSTEM_BIOS( 2, "v402", "Balcones Operating System v4.02" ) // Rank Xerox (European) boot ROM version of US 4.01
	ROMX_LOAD( "u33.4.02.rom", 0x0000, 0x0800, CRC(d9eb668e) SHA1(6acbef96e4e6526c58e068b7849fb9cce2ea2a10), ROM_BIOS(2) )
	ROMX_LOAD( "u34.4.02.rom", 0x0800, 0x0800, CRC(62181209) SHA1(2238aec096d19af9307bb294532f66f53dd7dfc3), ROM_BIOS(2) )
	ROMX_LOAD( "u35.4.02.rom", 0x1000, 0x0800, CRC(e22fbf6d) SHA1(6c162f79d42611176b0f1c0e8a4eeb07492beca1), ROM_BIOS(2) )
	ROMX_LOAD( "u36.rx11.4.02.rom", 0x1800, 0x0800, CRC(b6a239ce) SHA1(330d28fa8ec006d48d948b1c5e714ffced88fe90), ROM_BIOS(2) ) // supports low-profile keyboard, no input with the ROM present

	ROM_SYSTEM_BIOS( 3, "v403", "Balcones Operating System v4.03" ) // Incorporate programmable communications option and support for the low-profile keyboard (4-ROM set and type-ahead input buffer)
	ROMX_LOAD( "v403.u33", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(3) )
	ROMX_LOAD( "v403.u34", 0x0800, 0x0800, NO_DUMP, ROM_BIOS(3) )
	ROMX_LOAD( "v403.u35", 0x1000, 0x0800, NO_DUMP, ROM_BIOS(3) )
	ROMX_LOAD( "v403.u36", 0x1800, 0x0800, NO_DUMP, ROM_BIOS(3) )

	ROM_SYSTEM_BIOS( 4, "v404", "Balcones Operating System v4.04" ) // Changes sign-on message from Xerox 820-II to Xerox
	ROMX_LOAD( "537p3652.u33", 0x0000, 0x0800, CRC(7807cfbb) SHA1(bd3cc5cc5c59c84a50747aae5c17eb4617b0dbc3), ROM_BIOS(4) )
	ROMX_LOAD( "537p3653.u34", 0x0800, 0x0800, CRC(a9c6c0c3) SHA1(c2da9d1bf0da96e6b8bfa722783e411d2fe6deb9), ROM_BIOS(4) )
	ROMX_LOAD( "537p3654.u35", 0x1000, 0x0800, CRC(a8a07223) SHA1(e8ae1ebf2d7caf76771205f577b88ae493836ac9), ROM_BIOS(4) )
	ROMX_LOAD( "v404.u36", 0x1800, 0x0800, NO_DUMP, ROM_BIOS(4) ) // fitted for low-profile keyboard only

	ROM_SYSTEM_BIOS( 5, "v50", "Balcones Operating System v5.0" ) // Operating system modifications for DEM and new 5.25" disk controller (4 new boot ROMs)
	ROMX_LOAD( "u33.5.0_537p10828.bin", 0x0000, 0x0800, CRC(a17af0f1) SHA1(b1d9a151ed4558f49b3cdc1adbf348b54da48877), ROM_BIOS(5) )
	ROMX_LOAD( "u34.5.0_537p10829.bin", 0x0800, 0x0800, CRC(c9f5182e) SHA1(ac830848614cea984c849a42687ea2944d6765d9), ROM_BIOS(5) )
	ROMX_LOAD( "u35.5.0_537p10830.bin", 0x1000, 0x0800, CRC(278fa75f) SHA1(f47cf9eb30366211280f93a8460523fcc53eebe9), ROM_BIOS(5) )
	ROMX_LOAD( "v500.u36", 0x1800, 0x0800, NO_DUMP, ROM_BIOS(5) )

	ROM_SYSTEM_BIOS( 6, "v50v018", "Balcones Operating System v5.0 v018" ) // shows ROM ERROR
	ROMX_LOAD( "537p10828.u33.5.0.bin", 0x0000, 0x0800, CRC(a17af0f1) SHA1(b1d9a151ed4558f49b3cdc1adbf348b54da48877), ROM_BIOS(6) )
	ROMX_LOAD( "537p10829.u34.5.0.bin", 0x0800, 0x0800, CRC(c9f5182e) SHA1(ac830848614cea984c849a42687ea2944d6765d9), ROM_BIOS(6) )
	ROMX_LOAD( "537p10830.u35.5.0.bin", 0x1000, 0x0800, BAD_DUMP CRC(cc4e1c2b) SHA1(375bbed76d9088dec82b9599cd810727d3e605f3), ROM_BIOS(6) )
	ROMX_LOAD( "537p10831.u36.5.0.bin", 0x1800, 0x0800, CRC(cda7f598) SHA1(08ffd18959e1708136076c82486b8d121a04fa23), ROM_BIOS(6) )

	ROM_REGION( 0x1000, "chargen", 0 )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(0) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(0) )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(1) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(1) )

	ROMX_LOAD( "u57.04.north.rom", 0x0000, 0x0800, CRC(eda727a2) SHA1(292cd8a0dc6699c3a2091b20c0fc63d97a266fbf), ROM_BIOS(2) )
	ROMX_LOAD( "u58.03.north.rom", 0x0800, 0x0800, CRC(a2e514f3) SHA1(8ac22dd0cf0324a857718adf67b41912864893a3), ROM_BIOS(2)  )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(3) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(3) )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(4) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(4) )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(5) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(5) )

	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(6) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(6) )

ROM_END

ROM_START( x168 )
	ROM_REGION( 0x2000, Z80_TAG, 0 )
	ROM_DEFAULT_BIOS( "v404" )
	ROM_SYSTEM_BIOS( 0, "v404", "Balcones Operating System v4.04" ) // Changes sign-on message from Xerox 820-II to Xerox
	ROMX_LOAD( "537p3652.u33", 0x0000, 0x0800, CRC(7807cfbb) SHA1(bd3cc5cc5c59c84a50747aae5c17eb4617b0dbc3), ROM_BIOS(0) )
	ROMX_LOAD( "537p3653.u34", 0x0800, 0x0800, CRC(a9c6c0c3) SHA1(c2da9d1bf0da96e6b8bfa722783e411d2fe6deb9), ROM_BIOS(0) )
	ROMX_LOAD( "537p3654.u35", 0x1000, 0x0800, CRC(a8a07223) SHA1(e8ae1ebf2d7caf76771205f577b88ae493836ac9), ROM_BIOS(0) )
	ROMX_LOAD( "v404.u36", 0x1800, 0x0800, NO_DUMP, ROM_BIOS(0) ) // fitted for low-profile keyboard only

	ROM_SYSTEM_BIOS( 1, "v50", "Balcones Operating System v5.0" ) // Operating system modifications for DEM and new 5.25" disk controller (4 new boot ROMs)
	ROMX_LOAD( "l5.u33.rom", 0x0000, 0x0800, CRC(a17af0f1) SHA1(b1d9a151ed4558f49b3cdc1adbf348b54da48877), ROM_BIOS(1) )
	ROMX_LOAD( "l5.u34.rom", 0x0800, 0x0800, CRC(c9f5182e) SHA1(ac830848614cea984c849a42687ea2944d6765d9), ROM_BIOS(1) )
	ROMX_LOAD( "l5.u35.rom", 0x1000, 0x0800, BAD_DUMP CRC(44c8dbf8) SHA1(cba925b425a7a5ca68dc9fed10ea33e100704bf4), ROM_BIOS(1) )   // shows ROM ERROR and is different from Xerox 820-II v50
	ROMX_LOAD( "u36.rx024.rom", 0x1800, 0x0800, CRC(a7f1d677) SHA1(8c2a442f3a691f2e181a640d65f767ce3b51d711), ROM_BIOS(1) ) // fitted for low-profile keyboard only

	ROM_REGION( 0x1000, I8086_TAG, 0 )
	ROM_LOAD( "8086.u33", 0x0000, 0x1000, CRC(ee49e3dc) SHA1(a5f20c74fc53f9d695d8894534ab69a39e2c38d8) )

	ROM_REGION( 0x1000, "chargen", 0 )
	ROMX_LOAD( "x820ii.u57", 0x0000, 0x0800, CRC(1a50f600) SHA1(df4470c80611c14fa7ea8591f741fbbecdfe4fd9), ROM_BIOS(0) )
	ROMX_LOAD( "x820ii.u58", 0x0800, 0x0800, CRC(aca4b9b3) SHA1(77f41470b0151945b8d3c3a935fc66409e9157b3), ROM_BIOS(0) )

	ROMX_LOAD( "u57.04.north.rom", 0x0000, 0x0800, CRC(eda727a2) SHA1(292cd8a0dc6699c3a2091b20c0fc63d97a266fbf), ROM_BIOS(1) )
	ROMX_LOAD( "u58.03.north.rom", 0x0800, 0x0800, CRC(a2e514f3) SHA1(8ac22dd0cf0324a857718adf67b41912864893a3), ROM_BIOS(1)  )
ROM_END

ROM_START( mk83 )
	ROM_REGION( 0x1000, Z80_TAG, 0 )
	ROM_LOAD( "2732mk83.bin", 0x0000, 0x1000, CRC(a845c7e1) SHA1(3ccf629c5cd384953794ac4a1d2b45678bd40e92) )

	ROM_REGION( 0x800, "chargen", 0 )
	ROM_LOAD( "2716mk83.bin", 0x0000, 0x0800, CRC(10bf0d81) SHA1(7ec73670a4d9d6421a5d6a4c4edc8b7c87923f6c) )
ROM_END

/* System Drivers */

//    YEAR  NAME      PARENT    COMPAT  MACHINE     INPUT     CLASS             INIT        COMPANY                       FULLNAME        FLAGS
COMP( 1980, bigboard, 0,        0,      bigboard,   xerox820, bigboard_state,   empty_init, "Digital Research Computers", "Big Board",    0 )
COMP( 1981, x820,     bigboard, 0,      xerox820,   xerox820, xerox820_state,   empty_init, "Xerox",                      "Xerox 820",    MACHINE_NO_SOUND_HW )
COMP( 1982, mk82,     bigboard, 0,      bigboard,   xerox820, bigboard_state,   empty_init, "Scomar",                     "MK-82",        0 )
COMP( 1983, x820ii,   0,        0,      xerox820ii, xerox820, xerox820ii_state, empty_init, "Xerox",                      "Xerox 820-II", MACHINE_NOT_WORKING )
COMP( 1983, x168,     x820ii,   0,      xerox168,   xerox820, xerox820ii_state, empty_init, "Xerox",                      "Xerox 16/8",   MACHINE_NOT_WORKING )
COMP( 1983, mk83,     x820ii,   0,      mk83,       xerox820, xerox820_state,   empty_init, "Scomar",                     "MK-83",        MACHINE_NOT_WORKING | MACHINE_NO_SOUND_HW )