summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/drivers/mekd4.cpp
blob: d8856a1189363fbf5ca124f2e2e52e0779df45d9 (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
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
// license:BSD-3-Clause
// copyright-holders: 68bit
/******************************************************************************

Motorola Evaluation Kit 6809 D4 - MEK6809D4

Memory map

Range    Short  Description

0000-0fff RAM   User RAM, 4K, default location. It can be remapped to any 1K
                address boundary and on any RAM page, or disabled.

0000-7fff RAM   Off board RAM typically maps in this range, on any RAM page.

9000-9fff RAM   MEK68R2 Screen RAM

e000-e07f I/O   I/O1 Select Area
e080-e0ff I/O   I/O2 Select Area, includes system I/O below.

e0f1-e0ff SYSIO Onboard system I/O is always mapped to these addresses
                irrespective of the RAM or ROM pages.
e0f1-e0f1 Cfg   Read: 4-bit Config jumper; Write: RAM/ROM page latch
e0f2-e0f3 ACIA  Console RS-232
e0f4-e0f7 PIA   Stop on address comparator PIA. A0 and A1 are reversed.
e0f8-e0fb PIA   Keypad and LED display
e0fc-e0ff PIA   User PIA on Keypad-display board

e400-e7ff RAM   Onboad 1K stack RAM. Always mapped to these addresses
                irrespective of the RAM or ROM page.

e800-efff ROM   ROMG U61, normal location.
f000-ffff ROM   ROMH U62, normal location.


The onboard 4K user RAM can be placed at any 1K address boundary on any RAM
page and on multiple RAM pages. The default is 0x0000 to 0x0fff on all RAM
pages, but jumpers may be added at connector J2 to modify this selection. If a
jumper is present across pins 1-2, or 3-4, or 5-6, or 7-8, then address lines
A15 to A12 respectively must be high (rather than low) for the user RAM to be
selected. By default, with no jumpers installed, the RAM page address lines
RAP0 to RAP2 are 'do not care', but J2 pin pairs can be jumpered to select the
user RAM only when these are high or low - pins 9-10 select RAP0 being high,
pins 11-12 select RAP0 being low, pins 13-14 select RAP1 being high, etc. The
user RAM can also be disabled by jumpering any of pins 10, 12, 14, 16, 18, 20
low which can be done by jumpering any of these to any of pins 2, 4, 6, or 8.
The user RAM data bus is buffered and so long as it is decoded then the data
lines are driven so removing this RAM does not free the decoded address range,
and the onboard user RAM takes precedence over off board addressing. It would
cause a data bus conflict if the user RAM were decoded in the same address
range as the onboard stack RAM, ROM, or the system I/O. This user RAM can also
be write protected by removing the jumper between pins 11-12 at J1.

TODO implement the 4K user RAM mapping.

There are eight onboard ROM sockets, labeled ROM/A to ROM/H. ROM/A to ROM/D
have addressing for A0 to A12 so support 8K devices, however collectively
their A11 and/or A12 lines can be jumpered low or high to support smaller
devices. The ROM/E and ROM/F have addressing for A0 to A11 so support 4K
devices, but can be collectively jumpered for 1K, 2K or 4K operation. ROM/G
and ROM/H are used for the monitor ROMS and support 2K or 4K devices
individually, and the standard ROM sizes are 2K and 4K respectively. The
onboard ROM data bus is buffered and so long as it is decoded then the data
lines are driven so removing a ROM does not free the decoded address range,
and the onboard ROM takes precedence over off board addressing. It would cause
a data bus conflict if this ROM were decoded in the same address range as
the onboard stack RAM, the user RAM, or the system I/O. The data bus buffer
for the ROMs is not bi-directional, it would appear to not be possible to
place RAM or I/O in these sockets, and it appears that it would cause a bus
conflict if there were a valid write to these ROMs, and the W/R line is wired
to the ROM decoder to support that - not sure what was intended here?

The onboard ROM selection is handled by a 1K mapping ROM in U31. The outputs
D0 to D7 selecting ROM/A to ROM/H respectively when low. It was up to the
programming of this ROM to avoid address conflicts, to select only one ROM at
a time. The ROM address inputs A9 to A0 are respectively: A15, A14, A13, A12,
A11, A10, ROP2, ROP1, ROP0, R/W. This allows mapping ROMS on 1K address map
boundaries. The default mapping ROM was label "D4MAP 00", a MCM68A316, and did
not select any ROM 0x4000.

The mapping ROM pins 18 and 20 and wired to 0V, pin 21 is wired to +5V, pin
19 can be jumpered to 0V or 5V, defaulting to 0V. So could a single supply
EPROM could be substituted. Pin 19 is A10 on a 2716 EPROM the lower half of a
2K EPROM could be used too.

TODO implement the onboard ROMs and their mapping.

There was a resident editor assembler product available for this system, the
"MEK6809EAC Editor/Assembler V1.0 2/80". It was supplied on a tape and side
one had a version to load into RAM at 0100 to 2fff, and side two had a version
that was ROMable at a000 to cfff. It supported the MEK68R2 CRT display or a
terminal and object code could be placed in memory or saved on tape.

TODO This editor/assembler ROM might be a nice addition if it can be found.

The CPU clock is either generated from the onboard 3.579545 MHz XTAL or
externally as set via J3.

TODO could support 1MHz and 2MHz CPU operation.

The board includes a hardware 'stop' address comparator which compares the
A0-A15 address lines to the output of the PIA at e0f4-e0f7, 'stop_pia' here,
and asserts that PIA's CA1 input when they match. The monitor software uses
this to trigger an interrupt to implement code tracing. The PIA port B outputs
B0 to B7 are compared to the address lines A0 to A7 respectively, and the port
A outputs A0 to A7 are compared to the address lines A8 to A15
respectively. Notably the comparitor does not compare the RAM or ROM bank
lines, so this might be frustrating when used with code making use of
banking. It appears that the address comparator does not distinguish between
code versus data, so it would appear to be able to trigger on a data access
too, and although the monitor documenation does not mention such a use this
use is possible with the monitor. The trigger is also available at TP1 and
this could be informative in some hardware development, with the address set
and the interrupt disabled. The CA2 input can also be toggled low to generate
an interrupt as a manually 'abort'.


J1
1-2  RS-232 console
3-4  R2 board present
7-8  Keypad present
5-6  300/1200 cassette baud rate
11-12 Write protect 4K user ram.


ASCII terminal commands:
<hex addr><space> - Memory change
  <hex byte>      - enter data, write to memory.
  <space>         - increase address, same line
  <linefeed>      - increase address, new line
  '-' or '^'      - decrease address, new line
  ';'<hex addr>   - calculate branch offset to addr, 8 bit or 16 bit offset.
  <carriage return> - return from memory change
'R'               - Register editor
  'P'             - Program counter
  'A'             - A-Accumulator
  'B'             - B-Accumulator
  'X'             - X-Index
  'Y'             - Y-Index
  'C'             - Condition Codes
  'H'             - RAM/ROM pages select latch, high nibble is ROM page, low RAM page.
  'D'             - Direct Page
  'U'             - U-Stack
  'S'             - S-Stack
  '1','2','3','4' - Definable 16-bit registers (memory locations)
  <cr>            - exit register editor
  <linefeed>      - display update
  <space>         - next register
  'T'             - trace one instruction
  'L'             - trace one line (subroutine), using single stepping
  'R'             - trace one line (subroutine), using hardware (real time) approach.
'Q'               - Enter breakpoint editor
  'I'<addr>       - insert breakpoint at <addr>, to stop after one times.
  'I'<addr>;<n>   - insert breakpoint at <addr>, to stop after <n> times.
  'R'<addr>       - remove breakpoing at <addr>
  'S'<addr>       - set stop address, to stop after one times.
  'S'<addr>;<n>   - set stop address, to stop after <n> times.
  'K'             - clear all breakpoints and deactivate the stop address.
  <cr>            - exit breakpoint editor.
'G'               - Continue at the pseudo program counter.
<addr>'G'         - Go to user program at <addr>
'M'               - Memory dump
'P'               - Punch. Store information from memory to cassette.
<addr>'P'         - Punch with offset, as if starting from <addr>.
'L'               - Load. Read information to memory from cassette.
<addr>'L'         - Load with offset.
'V'               - Verify cassette data against memory.
<addr>'V'         - Verify with offset.
<hex>=            - Convert hex to decimal.
#<decimal>$       - Convert decimal to hex.
'U'               - Switch R2 to User screen page.
'S'               - Switch R2 to System screen page.
'X'               - Enter special functions.
  'M'             - Move memory.
  'F'             - Fill memory.
  'S'             - Search memory. Escape to pause.
  'A'             - ASCII Entry.
    '@'           - End of message.
    <escape>      - Exit ASCII entry.
    <delete>      - Delete last character.
    <backspace>   - When using R2D, back up.


MEK68KPD commands:

RS (Reset)  Reset, wired to the CPU reset line
EX (Escape) Typically aborts user program. Switch from CRT to KPD.
M (Memory display/change)
  Digits 5 and 6 show the entered data, and are blank unless it differs.
  Digits 7 and 8 show the actual data at the address.
  G  - increase the address.
  M  - decreases the address.
  FS - Offset calculation. Enter address, then press 'GO'.
    Last digit is S for a short offset and L for a long 16 bit offset.
    FS - stores the offset and returns to memory display and increased the address.
    FC - return to memory display at the same address.
  EX - exits memory display.
RD (Register display/alter)
  The 'HP' register is the hardware page register, upper nibble the ROM page,
  lower the RAM page, 8 pages each.
  The 'SA' register is the hardware stop address.
    FS - at register 'SA', to change the 'number of times'.
    FC - at register 'SA', to change the stop address.
  G   - advance to next register.
  M   - previous register.
  T/B - trace a single instruction
  P/L - trace user line, an entire subroutine if next, slow software version.
  RD  - trace user line, using the stop address hardware.
  EX  - exits register display.
GO to user program.
  If no address if entered then it uses the pseudo PC, it continues.
  Enter the address and press 'Go' to use that entered address.
  It firstly checks that there is RAM at the stack pointer.
FS GO - enter the address, then FS, then GO and it runs as a sub of the LED
  display code allowing use of the LED display. The sub should be quick
  relative to the 1ms display update period.
FS T/B - Breakpoint editor
  GO - advance to next breakpoing, up to 8, then loops.
  FC - deactivate breakpoint
  FS - edit the 'number of times before stopping' for the current entry.
  FS - enter an address then press FS to enter that as a breakpoint address
       and then edit the 'number of times before stopping'.
  EX - exits breakpoing editor.
P/L (Punch tape)
  Enter an address before P/L to set the apparent beginning address.
  At the 'b' prompt enter the beginning address of the data, then 'GO'.
  At the 'E' prompt enter the last address of the data.
  Start the tape and press GO. There is a 30 second leader of $ff.
FS P/L (Load from tape)
  Enter an address before FS for an offset load or verify??
FS 0 to F
  One of 16 user defined functions. Press FS then one number key 0 to F.
  Numeric data may be entered before pressing FS.
  A pointer to a table of 16 function address should be set at 0xe72e.
  There is a reservation at 0xe730-0xe74f for this table.
  The function address is stored in 0xe700 and called by the LED display
  update function PUT every 1msec.

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

#include "emu.h"

#include "bus/rs232/rs232.h"
#include "cpu/m6809/m6809.h"
#include "imagedev/cassette.h"
#include "imagedev/snapquik.h"
#include "machine/6821pia.h"
#include "machine/6850acia.h"
#include "machine/bankdev.h"
#include "machine/clock.h"
#include "machine/input_merger.h"
#include "machine/mc14411.h"
#include "machine/timer.h"
#include "sound/wave.h"
#include "video/pwm.h"

// MEK68R2
#include "machine/terminal.h"
#include "video/mc6845.h"

#include "emupal.h"
#include "render.h"
#include "screen.h"
#include "speaker.h"

#include "mekd4.lh"


class mekd4_state : public driver_device
{
public:
	mekd4_state(const machine_config &mconfig, device_type type, const char *tag)
		: driver_device(mconfig, type, tag)
		, m_maincpu(*this, "maincpu")
		, m_bankdev(*this, "bankdev")
		, m_stop_pia(*this, "stop_pia")
		, m_kpd_pia(*this, "kpd_pia")
		, m_display(*this, "display")
		, m_user_pia(*this, "user_pia")
		, m_brg(*this, "brg")
		, m_rs232_tx_baud(*this, "RS232_TX_BAUD")
		, m_rs232_rx_baud(*this, "RS232_RX_BAUD")
		, m_rs232_cts_route(*this, "RS232_CTS_ROUTE")
		, m_rs232_dcd_route(*this, "RS232_DCD_ROUTE")
		, m_acia(*this, "acia")
		, m_cass(*this, "cassette")
		, m_jumper1(*this, "JUMPER1")
		, m_keypad_columns(*this, "COL%u", 0)
		  // MEK68R2
		, m_mc6845(*this, "mc6845")
		, m_palette(*this, "palette")
		, m_screen(*this, "screen")
		, m_p_chargen(*this, "chargen")
		, m_video_ram(*this, "videoram")
		, m_r2_pia(*this, "r2_pia")
		, m_r2_mode(*this, "R2_MODE")
		, m_r2_display_nationality(*this, "R2_DISPLAY_NATIONALITY")
		, m_r2_display_format(*this, "R2_DISPLAY_FORMAT")
	{ }

	void mekd4(machine_config &config);
	void init_mekd4();

	DECLARE_WRITE_LINE_MEMBER(reset_key_w);
	DECLARE_INPUT_CHANGED_MEMBER(keypad_changed);
	DECLARE_INPUT_CHANGED_MEMBER(rs232_cts_route_change);
	DECLARE_INPUT_CHANGED_MEMBER(rs232_dcd_route_change);

private:
	uint8_t main_r(offs_t offset);
	void main_w(offs_t offset, uint8_t data);
	uint8_t config_r();
	void page_w(uint8_t data);
	uint8_t stop_pia_r(offs_t offset);
	void stop_pia_w(offs_t offset, uint8_t data);
	void stop_pia_pa_w(uint8_t data);
	void stop_pia_pb_w(uint8_t data);
	DECLARE_READ_LINE_MEMBER(stop_pia_ca2_r);
	uint16_t m_stop_address;

	DECLARE_WRITE_LINE_MEMBER(rs232_route_cts);
	DECLARE_WRITE_LINE_MEMBER(rs232_route_dcd);

	// Clocks
	DECLARE_WRITE_LINE_MEMBER(write_f1_clock);
	DECLARE_WRITE_LINE_MEMBER(write_f3_clock);
	DECLARE_WRITE_LINE_MEMBER(write_f7_clock);
	DECLARE_WRITE_LINE_MEMBER(write_f8_clock);
	DECLARE_WRITE_LINE_MEMBER(write_f9_clock);
	DECLARE_WRITE_LINE_MEMBER(write_f13_clock);

	DECLARE_READ_LINE_MEMBER(keypad_cb1_r);
	uint8_t keypad_key_r();
	void led_digit_w(uint8_t data);
	void led_segment_w(uint8_t data);

	DECLARE_READ_LINE_MEMBER(stop_pia_cb1_r);
	DECLARE_WRITE_LINE_MEMBER(stop_pia_cb2_w);

	void mekd4_stop_mem(address_map &map);
	void mekd4_mem(address_map &map);

	address_space *m_banked_space;

	bool keypad_key_pressed();

	uint32_t screen_update(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect);

	uint8_t m_rom_page; // aka ROP0, ROP1, ROP2
	uint8_t m_ram_page; // aka RAP0, RAP1, RAP2
	uint8_t m_segment;
	uint8_t m_digit;
	virtual void machine_start() override;
	virtual void machine_reset() override;
	required_device<cpu_device> m_maincpu;
	required_device<address_map_bank_device> m_bankdev;
	required_device<pia6821_device> m_stop_pia;
	required_device<pia6821_device> m_kpd_pia;
	required_device<pwm_display_device> m_display;
	required_device<pia6821_device> m_user_pia;
	required_device<mc14411_device> m_brg;
	required_ioport m_rs232_tx_baud;
	required_ioport m_rs232_rx_baud;
	required_ioport m_rs232_cts_route;
	required_ioport m_rs232_dcd_route;
	required_device<acia6850_device> m_acia;
	required_device<cassette_image_device> m_cass;
	required_ioport m_jumper1;
	required_ioport_array<4> m_keypad_columns;
	int m_cts;
	int m_dcd;

	// MEK68R2
	MC6845_UPDATE_ROW(update_row);
	uint8_t r2_pia_pa_r();
	uint8_t r2_pia_pb_r();
	DECLARE_WRITE_LINE_MEMBER(r2_hsync_changed);
	DECLARE_WRITE_LINE_MEMBER(r2_vsync_changed);
	DECLARE_READ_LINE_MEMBER(r2_pia_cb1_r);
	optional_device<mc6845_device> m_mc6845;
	optional_device<palette_device> m_palette;
	optional_device<screen_device> m_screen;
	optional_region_ptr<uint8_t> m_p_chargen;
	optional_shared_ptr<uint8_t> m_video_ram;
	optional_device<pia6821_device> m_r2_pia;
	optional_ioport m_r2_mode;
	optional_ioport m_r2_display_nationality;
	optional_ioport m_r2_display_format;
	void kbd_put(uint8_t data);
	uint8_t m_term_data;
	bool m_r2_vsync;
};



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

    Address Map

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

void mekd4_state::mekd4_stop_mem(address_map &map)
{
	map(0x0000, 0xffff).rw(FUNC(mekd4_state::main_r), FUNC(mekd4_state::main_w));
}

void mekd4_state::mekd4_mem(address_map &map)
{
	map(0x0000, 0x7fff).ram();

	/* MEK68R2 Video RAM 9000-9fff */
	map(0x9000, 0x9fff).ram().share(m_video_ram);

	/* MEK68VG VDG Scroll register f040-f041 */

	/* MEK68R2 CRT register f042-f043 */
	map(0xe042, 0xe042).w(m_mc6845, FUNC(mc6845_device::address_w));
	map(0xe043, 0xe043).rw(m_mc6845, FUNC(mc6845_device::register_r), FUNC(mc6845_device::register_w));

	/* MEK68R2 PIA (Keyboard) */
	map(0xe044, 0xe047).rw(m_r2_pia, FUNC(pia6821_device::read), FUNC(pia6821_device::write));

	map(0xe0f1, 0xe0f1).rw(FUNC(mekd4_state::config_r), FUNC(mekd4_state::page_w));
	map(0xe0f2, 0xe0f3).rw(m_acia, FUNC(acia6850_device::read), FUNC(acia6850_device::write));
	map(0xe0f4, 0xe0f7).rw(FUNC(mekd4_state::stop_pia_r), FUNC(mekd4_state::stop_pia_w));
	map(0xe0f8, 0xe0fb).rw(m_kpd_pia, FUNC(pia6821_device::read), FUNC(pia6821_device::write));
	map(0xe0fc, 0xe0ff).rw(m_user_pia, FUNC(pia6821_device::read), FUNC(pia6821_device::write));

	map(0xe400, 0xe7ff).ram();

	map(0xe800, 0xefff).rom();
	map(0xf000, 0xffff).rom();
}

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

    Keys

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

static INPUT_PORTS_START(mekd4)

	PORT_START("JUMPER1")
	PORT_DIPNAME(0x01, 0x00, "RS-232 console (D4B)")
	PORT_DIPSETTING(0x00, DEF_STR(On))
	PORT_DIPSETTING(0x01, DEF_STR(Off))
	PORT_DIPNAME(0x02, 0x00, "MEK68R2 present (D4C)")
	PORT_DIPSETTING(0x00, DEF_STR(On))
	PORT_DIPSETTING(0x02, DEF_STR(Off))
	PORT_DIPNAME(0x04, 0x00, "Cassette baud rate")
	PORT_DIPSETTING(0x00, "1200")
	PORT_DIPSETTING(0x04, "300")
	PORT_DIPNAME(0x08, 0x00, "Keypad and display present (D4A)")
	PORT_DIPSETTING(0x00, DEF_STR(On))
	PORT_DIPSETTING(0x08, DEF_STR(Off))

	PORT_START("RS232_TX_BAUD")
	PORT_CONFNAME(0x3f, 1, "RS232 TX Baud Rate")
	PORT_CONFSETTING(0x20, "110")
	PORT_CONFSETTING(0x10, "300")
	PORT_CONFSETTING(0x08, "600")
	PORT_CONFSETTING(0x04, "1200")
	PORT_CONFSETTING(0x02, "4800")
	PORT_CONFSETTING(0x01, "9600")

	PORT_START("RS232_RX_BAUD")
	PORT_CONFNAME(0x3f, 1, "RS232 RX Baud Rate")
	PORT_CONFSETTING(0x20, "110")
	PORT_CONFSETTING(0x10, "300")
	PORT_CONFSETTING(0x08, "600")
	PORT_CONFSETTING(0x04, "1200")
	PORT_CONFSETTING(0x02, "4800")
	PORT_CONFSETTING(0x01, "9600")

	// RS232 CTS and DCD routing at the RS232 Conn. These need to be
	// jumpered to logical low if not driven by the RS232 device. There is
	// +12 and -12V available at this connector for this purpose.
	PORT_START("RS232_CTS_ROUTE")
	PORT_CONFNAME(0x1, 0, "RS232 CTS") PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, rs232_cts_route_change, 0)
	PORT_CONFSETTING(0, "Jumper low")
	PORT_CONFSETTING(1, "Pass through")
	PORT_START("RS232_DCD_ROUTE")
	PORT_CONFNAME(0x1, 0, "RS232 DCD") PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, rs232_dcd_route_change, 0)
	PORT_CONFSETTING(0, "Jumper low")
	PORT_CONFSETTING(1, "Pass through")

	// RESET is not wired to the key matrix.
	PORT_START("RESET")
	PORT_BIT(0x01, IP_ACTIVE_LOW, IPT_KEYPAD) PORT_NAME("RS") PORT_WRITE_LINE_DEVICE_MEMBER(DEVICE_SELF, mekd4_state, reset_key_w)

	// PORT_CODEs are not assigned to the keypad to allow it on screen at
	// the same time as the terminal or CRT console which also receive
	// keyboard inputs. When a keyboard is available the keypad is of
	// limited use, but still useful to interrupt code or reset the
	// machine. If MAME someday allows the keyboard input focus to be
	// switched then this might be redesigned.
	PORT_START("COL0")
	PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("M")
	PORT_BIT(0x10, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("FS")
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("7")
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("4")
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("1")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("0")

	PORT_START("COL1")
	PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("EX")
	PORT_BIT(0x10, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("FC")
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("8")
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("5")
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("2")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("F")

	PORT_START("COL2")
	PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("RD")
	PORT_BIT(0x10, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("P/L")
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("9")
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("6")
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("3")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("E")

	PORT_START("COL3")
	PORT_BIT(0x20, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("GO")
	PORT_BIT(0x10, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("T/B")
	PORT_BIT(0x08, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("A")
	PORT_BIT(0x04, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("B")
	PORT_BIT(0x02, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("C")
	PORT_BIT(0x01, IP_ACTIVE_HIGH, IPT_KEYBOARD) PORT_CHANGED_MEMBER(DEVICE_SELF, mekd4_state, keypad_changed, 0) PORT_NAME("D")

	// MEK68R2

	PORT_START("R2_MODE")
	PORT_DIPNAME(0x1, 0, "R2 Mode")
	PORT_DIPSETTING(0, "Normal")
	PORT_DIPSETTING(1, "Dumb terminal")

	PORT_START("R2_DISPLAY_NATIONALITY")
	PORT_DIPNAME(0x1, 1, "Display nationality")
	PORT_DIPSETTING(0, "US")
	PORT_DIPSETTING(1, "Europe")

	PORT_START("R2_DISPLAY_FORMAT")
	PORT_DIPNAME(0x0003, 2, "Display format")
	PORT_DIPSETTING(0, "16 lines of 32 characters")
	PORT_DIPSETTING(1, "16 lines of 64 characters")
	PORT_DIPSETTING(2, "20 lines of 80 characters")
	PORT_DIPSETTING(3, "User defined")

INPUT_PORTS_END


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

 Stop comparitor.

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

uint8_t mekd4_state::main_r(offs_t offset)
{
	if (offset == m_stop_address && !machine().side_effects_disabled())
	{
		m_stop_pia->ca1_w(CLEAR_LINE);
		m_stop_pia->ca1_w(ASSERT_LINE);
		m_stop_pia->ca1_w(CLEAR_LINE);
	}
	return m_banked_space->read_byte(offset);
}

void mekd4_state::main_w(offs_t offset, uint8_t data)
{
	if (offset == m_stop_address && !machine().side_effects_disabled())
	{
		m_stop_pia->ca1_w(CLEAR_LINE);
		m_stop_pia->ca1_w(ASSERT_LINE);
		m_stop_pia->ca1_w(CLEAR_LINE);
	}
	m_banked_space->write_byte(offset, data);
}

uint8_t mekd4_state::config_r()
{
	return 0xf0 | m_jumper1->read();
}

// The design reversed the A0 and A1 lines so that
// a 16 bit write could write both data addresses.
uint8_t mekd4_state::stop_pia_r(offs_t offset)
{
	// Reverse the A0 and A1 address lines;
	int8_t reversed = BIT(offset, 0) << 1 | BIT(offset, 1);
	return m_stop_pia->read(reversed);
}

void mekd4_state::stop_pia_w(offs_t offset, uint8_t data)
{
	// Reverse the A0 and A1 address lines;
	int8_t reversed = BIT(offset, 0) << 1 | BIT(offset, 1);
	m_stop_pia->write(reversed, data);
}

void mekd4_state::stop_pia_pa_w(uint8_t data)
{
	m_stop_address = (m_stop_address & 0x00ff) | (data << 8);
}

void mekd4_state::stop_pia_pb_w(uint8_t data)
{
	m_stop_address = (m_stop_address & 0xff00) | data;
}

// Connected to 'abort' TP2. Can be toggled low to and abort user code.
READ_LINE_MEMBER(mekd4_state::stop_pia_ca2_r)
{
	return 1;
}

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

 RAM and ROM paging

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

void mekd4_state::page_w(uint8_t data)
{
	m_rom_page = data & 0x07;
	m_ram_page = (data >> 4) & 0x07;
}

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

    Keypad

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

WRITE_LINE_MEMBER(mekd4_state::reset_key_w)
{
	m_maincpu->set_input_line(INPUT_LINE_RESET, state ? CLEAR_LINE : ASSERT_LINE);

	// TODO reset other devices.
}

bool mekd4_state::keypad_key_pressed()
{
	return (m_keypad_columns[0]->read() & m_digit) ||
		(m_keypad_columns[1]->read() & m_digit) ||
		(m_keypad_columns[2]->read() & m_digit) ||
		(m_keypad_columns[3]->read() & m_digit);
}

INPUT_CHANGED_MEMBER(mekd4_state::keypad_changed)
{
	m_kpd_pia->cb1_w(mekd4_state::keypad_key_pressed());
}

READ_LINE_MEMBER(mekd4_state::keypad_cb1_r)
{
	return mekd4_state::keypad_key_pressed();
}

uint8_t mekd4_state::keypad_key_r()
{
	uint8_t mux = (m_digit & 0xc0) >> 6;
	uint8_t i = (m_keypad_columns[mux]->read() & m_digit) ? 0 : 0x80;

	return i | m_segment;
}

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

    Seven segment LED display

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

// PA
void mekd4_state::led_segment_w(uint8_t data)
{
	m_segment = data & 0x7f;
	m_display->matrix(m_digit, ~m_segment);
}

// PB
void mekd4_state::led_digit_w(uint8_t data)
{
	m_digit = data;
	m_display->matrix(m_digit, ~m_segment);
	// Update the keypad pressed output which depends on m_digit.
	m_kpd_pia->cb1_w(mekd4_state::keypad_key_pressed());
}


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

  Cassette

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

READ_LINE_MEMBER(mekd4_state::stop_pia_cb1_r)
{
	uint8_t state = m_cass->input() > +0.0;
	return state;
}

WRITE_LINE_MEMBER(mekd4_state::stop_pia_cb2_w)
{
	m_cass->output(state ? -1.0 : +1.0);
}

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

  ACIA

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

WRITE_LINE_MEMBER(mekd4_state::rs232_route_cts)
{
	if (m_rs232_cts_route->read())
		m_acia->write_cts(state);

	// Cache the state, in case the ioport setting changes.
	m_cts = state;
}

WRITE_LINE_MEMBER(mekd4_state::rs232_route_dcd)
{
	if (m_rs232_dcd_route->read())
		m_acia->write_dcd(state);

	// Cache the state, in case the ioport setting changes.
	m_dcd = state;
}

INPUT_CHANGED_MEMBER(mekd4_state::rs232_cts_route_change)
{
	if (newval)
		m_acia->write_cts(m_cts);
	else
		m_acia->write_cts(0);
}

INPUT_CHANGED_MEMBER(mekd4_state::rs232_dcd_route_change)
{
	if (newval)
		m_acia->write_dcd(m_dcd);
	else
		m_acia->write_dcd(0);
}

WRITE_LINE_MEMBER(mekd4_state::write_f1_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 0))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 0))
		m_acia->write_rxc(state);
}

WRITE_LINE_MEMBER(mekd4_state::write_f3_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 1))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 1))
		m_acia->write_rxc(state);
}

WRITE_LINE_MEMBER(mekd4_state::write_f7_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 2))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 2))
		m_acia->write_rxc(state);
}

WRITE_LINE_MEMBER(mekd4_state::write_f8_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 3))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 3))
		m_acia->write_rxc(state);
}

WRITE_LINE_MEMBER(mekd4_state::write_f9_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 4))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 4))
		m_acia->write_rxc(state);
}

WRITE_LINE_MEMBER(mekd4_state::write_f13_clock)
{
	if (BIT(m_rs232_tx_baud->read(), 5))
		m_acia->write_txc(state);
	if (BIT(m_rs232_rx_baud->read(), 5))
		m_acia->write_rxc(state);
}

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

  MEK68R2

  This might in future be moved to a slot device, on a bus.

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

// Delivery of keyboard inputs to the MEK68R2 keyboard is disabled when on
// views with the RS232 terminal, assuming that this keyboard is not present.
// Also disable delivery when the 'MEK68R2 present' jumper indicates it is
// disabled, assuming that this keyboard is not present.
void mekd4_state::kbd_put(uint8_t data)
{
	uint8_t view = machine().render().first_target()->view();
	if (view == 0)
		return;

	if (BIT(m_jumper1->read(), 1))
		return;

	m_term_data = data;
	// Triggers on the falling edge.
	m_r2_pia->ca1_w(ASSERT_LINE);
	m_r2_pia->ca1_w(CLEAR_LINE);
	m_r2_pia->ca1_w(ASSERT_LINE);
}

// PA0 to PA6 - Keyboard data.
// PA7 - Display nationality, 0 USA, 1 Europe.
uint8_t mekd4_state::r2_pia_pa_r()
{
	uint8_t ret = m_term_data;
	int8_t display_nationality = m_r2_display_nationality->read();
	m_term_data = 0;
	return ret | (display_nationality << 7);
}

// PB0 - Mode: 0 normal, 1 dumb terminal.
// PB1,2,3 - N/C
// PB4 - User defined
// PB5 - Light pen control.
// PB7, PB6 - Display format.
//       00 - 16 lines of 32 characters.
//       01 - 16 lines of 64 characters.
//       10 - 20 lines of 80 characters.
//       11 - User defined.
uint8_t mekd4_state::r2_pia_pb_r()
{
	int8_t display_format = m_r2_display_format->read();
	int8_t mode = m_r2_mode->read();
	return (display_format << 6) | mode;
}

WRITE_LINE_MEMBER(mekd4_state::r2_hsync_changed)
{
	m_r2_pia->cb2_w(state);
}

WRITE_LINE_MEMBER(mekd4_state::r2_vsync_changed)
{
	m_r2_vsync = state;
	m_r2_pia->cb1_w(state);
}

READ_LINE_MEMBER(mekd4_state::r2_pia_cb1_r)
{
	return m_r2_vsync;
}

MC6845_UPDATE_ROW(mekd4_state::update_row)
{
	const pen_t *pen = m_palette->pens();

	int x = 0;

	for (int column = 0; column < x_count; column++)
	{
		uint8_t code = m_video_ram[(ma + column) & 0xfff];
		int dcursor = (column == cursor_x);

		if (BIT(code, 7)) {
			/* Lores 6 pixel character.
			     -----------
			     | D1 | D0 |
			     | D3 | D2 |
			     | D5 | D4 |
			     -----------
			     D6 - 1 Grey tone, 0 brightness.
			*/
			int pixel = ((ra & 0x0c) >> 1) + 1;
			int dout = BIT(code, pixel);
			int grey = BIT(code, 6);
			int color = ((dcursor ^ dout) && de) << (grey ^ 1);
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
			pixel--;
			dout = BIT(code, pixel);
			color = ((dcursor ^ dout) && de) << (grey ^ 1);
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
			bitmap.pix(y, x++) = pen[color];
		} else {
			offs_t address = ra < 8 ? ((code & 0x7f) << 3) | (ra & 0x07) : 0;
			uint8_t data = m_p_chargen[address];

			for (int bit = 0; bit < 8; bit++)
			{
				int dout = BIT(data, 7);
				int color = ((dcursor ^ dout) && de) << 1;

				bitmap.pix(y, x++) = pen[color];

				data <<= 1;
			}
		}
	}
}


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

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

void mekd4_state::init_mekd4()
{
}

void mekd4_state::machine_start()
{
	m_banked_space = &subdevice<address_map_bank_device>("bankdev")->space(AS_PROGRAM);

	save_item(NAME(m_stop_address));
	save_item(NAME(m_rom_page));
	save_item(NAME(m_ram_page));
	save_item(NAME(m_segment));
	save_item(NAME(m_digit));
	save_item(NAME(m_cts));
	save_item(NAME(m_dcd));
	save_item(NAME(m_term_data));
	save_item(NAME(m_r2_vsync));
}

void mekd4_state::machine_reset()
{
	m_rom_page = 0;
	m_ram_page = 0;
	m_stop_address = 0x0000;

	// Avoid triggering an early interrupt when CB1 lowered. The mc6821
	// driver resets CB1 high and to trigger on a high to low
	// transition. The mekd4 programs CB1 to trigger on a low to high
	// transition and configuring this earlier here is adequate.
	m_kpd_pia->write(1, 2);
	m_kpd_pia->cb2_w(ASSERT_LINE);  // Pulled high.

	m_brg->rsa_w(CLEAR_LINE);
	m_brg->rsb_w(ASSERT_LINE);

	// Write low here if jumpered low.
	if (!m_rs232_cts_route->read())
		m_acia->write_cts(0);
	if (!m_rs232_dcd_route->read())
		m_acia->write_dcd(0);

	// MEK68R2
	m_r2_pia->ca1_w(ASSERT_LINE);
	m_r2_pia->ca2_w(ASSERT_LINE);
	m_r2_vsync = 0;
	m_r2_pia->cb1_w(m_r2_vsync);
	m_r2_pia->cb2_w(0);
}

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

    Machine

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

static DEVICE_INPUT_DEFAULTS_START(terminal)
	DEVICE_INPUT_DEFAULTS("RS232_RXBAUD", 0xff, RS232_BAUD_9600)
	DEVICE_INPUT_DEFAULTS("RS232_TXBAUD", 0xff, RS232_BAUD_9600)
	DEVICE_INPUT_DEFAULTS("RS232_STARTBITS", 0xff, RS232_STARTBITS_1)
	DEVICE_INPUT_DEFAULTS("RS232_DATABITS", 0xff, RS232_DATABITS_8)
	DEVICE_INPUT_DEFAULTS("RS232_PARITY", 0xff, RS232_PARITY_NONE)
	DEVICE_INPUT_DEFAULTS("RS232_STOPBITS", 0xff, RS232_STOPBITS_1)
DEVICE_INPUT_DEFAULTS_END

void mekd4_state::mekd4(machine_config &config)
{
	MC6809(config, m_maincpu, 3.579545_MHz_XTAL);
	m_maincpu->set_addrmap(AS_PROGRAM, &mekd4_state::mekd4_stop_mem);

	ADDRESS_MAP_BANK(config, m_bankdev, 0);
	m_bankdev->set_endianness(ENDIANNESS_BIG);
	m_bankdev->set_data_width(8);
	m_bankdev->set_addr_width(20);
	m_bankdev->set_addrmap(AS_PROGRAM, &mekd4_state::mekd4_mem);

	INPUT_MERGER_ANY_HIGH(config, "mainirq").output_handler().set_inputline(m_maincpu, M6809_IRQ_LINE);
	INPUT_MERGER_ANY_HIGH(config, "mainnmi").output_handler().set_inputline(m_maincpu, INPUT_LINE_NMI);

	/* LED display */
	PWM_DISPLAY(config, m_display).set_size(8, 7);
	m_display->set_segmask(0xff, 0x7f);

	config.set_default_layout(layout_mekd4);

	SPEAKER(config, "mono").front_center();

	CASSETTE(config, m_cass);
	m_cass->set_default_state(CASSETTE_STOPPED | CASSETTE_MOTOR_ENABLED | CASSETTE_SPEAKER_ENABLED);
	m_cass->add_route(ALL_OUTPUTS, "mono", 0.05);

	// IRQ is not connected. RTS, CTS, and DCD are available.
	ACIA6850(config, m_acia, 0);
	m_acia->txd_handler().set("rs232", FUNC(rs232_port_device::write_txd));
	m_acia->rts_handler().set("rs232", FUNC(rs232_port_device::write_rts));

	MC14411(config, m_brg, XTAL(1'843'200));
	m_brg->out_f<1>().set(FUNC(mekd4_state::write_f1_clock));
	m_brg->out_f<3>().set(FUNC(mekd4_state::write_f3_clock));
	m_brg->out_f<7>().set(FUNC(mekd4_state::write_f7_clock));
	m_brg->out_f<8>().set(FUNC(mekd4_state::write_f8_clock));
	m_brg->out_f<9>().set(FUNC(mekd4_state::write_f9_clock));
	m_brg->out_f<13>().set(FUNC(mekd4_state::write_f13_clock));

	rs232_port_device &rs232(RS232_PORT(config, "rs232", default_rs232_devices, "terminal"));
	rs232.rxd_handler().set(m_acia, FUNC(acia6850_device::write_rxd));
	rs232.cts_handler().set(FUNC(mekd4_state::rs232_route_cts));
	rs232.dcd_handler().set(FUNC(mekd4_state::rs232_route_dcd));
	rs232.set_option_device_input_defaults("terminal", DEVICE_INPUT_DEFAULTS_NAME(terminal));

	// Stop PIA. IRQB is NC.
	PIA6821(config, m_stop_pia, 0);
	m_stop_pia->writepa_handler().set(FUNC(mekd4_state::stop_pia_pa_w));
	m_stop_pia->writepb_handler().set(FUNC(mekd4_state::stop_pia_pb_w));
	m_stop_pia->readca2_handler().set(FUNC(mekd4_state::stop_pia_ca2_r));
	m_stop_pia->readcb1_handler().set(FUNC(mekd4_state::stop_pia_cb1_r));
	m_stop_pia->cb2_handler().set(FUNC(mekd4_state::stop_pia_cb2_w));
	m_stop_pia->irqa_handler().set("mainnmi", FUNC(input_merger_device::in_w<0>));

	// Keypad and display PIA. CA1, CA2, IRQA are NC. CB2 is pulled high.
	PIA6821(config, m_kpd_pia, 0);
	m_kpd_pia->readpa_handler().set(FUNC(mekd4_state::keypad_key_r));
	m_kpd_pia->readcb1_handler().set(FUNC(mekd4_state::keypad_cb1_r));
	m_kpd_pia->writepa_handler().set(FUNC(mekd4_state::led_segment_w));
	m_kpd_pia->writepb_handler().set(FUNC(mekd4_state::led_digit_w));
	m_kpd_pia->irqb_handler().set("mainnmi", FUNC(input_merger_device::in_w<1>));

	// Keypad and display board User PIA.
	PIA6821(config, m_user_pia, 0);
	m_user_pia->irqa_handler().set("mainirq", FUNC(input_merger_device::in_w<0>));
	m_user_pia->irqb_handler().set("mainirq", FUNC(input_merger_device::in_w<1>));

	// MEK68R2

	SCREEN(config, m_screen, SCREEN_TYPE_RASTER);

	m_screen->set_refresh_hz(50);
	m_screen->set_size(80 * 8 + 80 * 10, 20 * 12 + 100);
	m_screen->set_visarea(0, 80 * 8 + 80 * 10 - 1, 0, 20 * 12 + 100 - 1);
	m_screen->set_screen_update("mc6845", FUNC(mc6845_device::screen_update));

	PALETTE(config, m_palette, palette_device::MONOCHROME_HIGHLIGHT);

	MC6845(config, m_mc6845, XTAL(14'318'181)/8);
	m_mc6845->set_screen(m_screen);
	m_mc6845->set_show_border_area(false);
	m_mc6845->set_char_width(8);
	m_mc6845->set_update_row_callback(FUNC(mekd4_state::update_row));
	m_mc6845->out_hsync_callback().set(FUNC(mekd4_state::r2_hsync_changed));
	m_mc6845->out_vsync_callback().set(FUNC(mekd4_state::r2_vsync_changed));

	// PA is the keyboard data and a mode flag.
	// CA1 is keyboard strobe.
	// CA2 light pen input.
	// PB0 is mode flags and light pen control.
	// CB1 is VSYNC, and CB2 is HSYNC.
	PIA6821(config, m_r2_pia, 0);
	m_r2_pia->readpa_handler().set(FUNC(mekd4_state::r2_pia_pa_r));
	m_r2_pia->readpb_handler().set(FUNC(mekd4_state::r2_pia_pb_r));
	m_r2_pia->readcb1_handler().set(FUNC(mekd4_state::r2_pia_cb1_r));
	m_r2_pia->irqa_handler().set("mainirq", FUNC(input_merger_device::in_w<2>));
	m_r2_pia->irqb_handler().set("mainirq", FUNC(input_merger_device::in_w<3>));

	generic_keyboard_device &keyboard(GENERIC_KEYBOARD(config, "keyboard", 0));
	keyboard.set_keyboard_callback(FUNC(mekd4_state::kbd_put));
}

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

    ROMS

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

ROM_START(mekd4)
	ROM_REGION(0x10000,"bankdev",0)
	ROM_LOAD("d4bugr2.rom", 0xe800, 0x0800, CRC(0b80a67d) SHA1(20d980767a7a667fe0f8e377bb2c29e297e6c635))
	ROM_LOAD("d4bugkpd.rom", 0xf000, 0x1000, CRC(1fdf414a) SHA1(3c8883a6ee0ae89398d9be5a5843db4c3b20f7fd))
	ROM_REGION(0x0400, "chargen",0)
	ROM_LOAD("mcm6674p.chr", 0x0000, 0x0400, CRC(1c22088a) SHA1(b5f0bd0cfdec0cd5c1cb764506bef3c17d6af0eb))
	ROM_REGION(0x0400, "rommap",0)
	ROM_LOAD("d4map00.rom", 0x0000, 0x0400, CRC(7e676444) SHA1(4f8a7443da509561be958786f9bd72eac3969a89))
ROM_END

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

  Game driver(s)

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

//    YEAR  NAME    PARENT  COMPAT  MACHINE   INPUT  CLASS        INIT        COMPANY     FULLNAME      FLAGS
COMP(1980, mekd4,  0,      0,      mekd4,    mekd4, mekd4_state, init_mekd4, "Motorola", "MEK6802D4" , MACHINE_NO_SOUND)