summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/machine/lynx.cpp
blob: 0f2a17b12fbf9114b2e50bcbe08820cd6aa4e86c (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
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
// license:GPL-2.0+
// copyright-holders:Peter Trauner
/******************************************************************************
 PeT mess@utanet.at 2000,2001
******************************************************************************/

#include "emu.h"
#include "includes/lynx.h"
#include "cpu/m6502/m65sc02.h"
#include "render.h"

#define PAD_UP      0x80
#define PAD_DOWN    0x40
#define PAD_LEFT    0x20
#define PAD_RIGHT   0x10


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

    Graphics Drawing

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

/* modes from blitter command */
enum {
	BACKGROUND = 0,
	BACKGROUND_NO_COLL,
	BOUNDARY_SHADOW,
	BOUNDARY,
	NORMAL_SPRITE,
	NO_COLL,
	XOR_SPRITE,
	SHADOW
};

uint8_t lynx_state::lynx_read_ram(uint16_t address)
{
	uint8_t result = 0x00;
	if (address <= 0xfbff)
		result = m_mem_0000[address - 0x0000];
	else if (address <= 0xfcff)
		result = m_mem_fc00[address - 0xfc00];
	else if (address <= 0xfdff)
		result = m_mem_fd00[address - 0xfd00];
	else if (address <= 0xfff7)
		result = m_mem_fe00[address - 0xfe00];
	else if (address >= 0xfffa)
		result = m_mem_fffa[address - 0xfffa];
	return result;
}

void lynx_state::lynx_write_ram(uint16_t address, uint8_t data)
{
	if (address <= 0xfbff)
		m_mem_0000[address - 0x0000] = data;
	else if (address <= 0xfcff)
		m_mem_fc00[address - 0xfc00] = data;
	else if (address <= 0xfdff)
		m_mem_fd00[address - 0xfd00] = data;
	else if (address <= 0xfff7)
		m_mem_fe00[address - 0xfe00] = data;
	else if (address >= 0xfffa)
		m_mem_fffa[address - 0xfffa] = data;
}

/* The pen numbers range from '0' to 'F. Pen numbers '1' through 'D' are always collidable and opaque. The other
ones have different behavior depending on the sprite type: there are 8 types of sprites, each has different
characteristics relating to some or all of their pen numbers.

* Shadow Error: The hardware is missing an inverter in the 'shadow' generator. This causes sprite types that
did not invoke shadow to now invoke it and vice versa. The only actual functionality loss is that 'exclusive or'
sprites and 'background' sprites will have shadow enabled.

The sprite types relate to specific hardware functions according to the following table:


   -------------------------- SHADOW
  |   ----------------------- BOUNDARY_SHADOW
  |  |   -------------------- NORMAL_SPRITE
  |  |  |   ----------------- BOUNDARY
  |  |  |  |   -------------- BACKGROUND (+ shadow, due to bug in 'E' pen)
  |  |  |  |  |   ----------- BACKGROUND_NO_COLL
  |  |  |  |  |  |   -------- NO_COLL
  |  |  |  |  |  |  |   ----- XOR_SPRITE (+ shadow, due to bug in 'E' pen)
  |  |  |  |  |  |  |  |
  1  0  1  0  1  1  1  1      F is opaque
  0  0  1  1  0  0  0  0      E is collideable
  0  0  1  1  0  0  0  0      0 is opaque and collideable
  1  1  1  1  0  0  0  1      allow collision detect
  1  1  1  1  1  0  0  1      allow coll. buffer access
  0  0  0  0  0  0  0  1      exclusive-or the data
*/

inline void lynx_state::lynx_plot_pixel(const int mode, const int16_t x, const int y, const int color)
{
	uint8_t back;
	uint16_t screen;
	uint16_t colbuf;

	m_blitter.everon = true;
	screen = m_blitter.screen + y * 80 + x / 2;
	colbuf = m_blitter.colbuf + y * 80 + x / 2;

	/* a note on timing: The hardware packs the pixel data and updates the screen and collision buffer a byte at a time.
	Thus the buffer update for two pixels takes 3 memory accesses for a normal sprite (write to screen buffer, read/write to collision buffer).
	+1 memory access for palette fetch?
	*/

	switch (mode&0x7)
	{
		case NORMAL_SPRITE:
		/* A sprite may be set to 'normal'. This means that pen number '0' will be transparent and
		non-collideable. All other pens will be opaque and collideable */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0x0f) | (color << 4));
				m_blitter.memory_accesses++;

				if(m_blitter.sprite_collide && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					m_blitter.memory_accesses += 2;
					if ((back >> 4) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0xf0) | color);

				if(m_blitter.sprite_collide && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
					if ((back & 0x0f) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
			}
			break;

		case BOUNDARY:
		/* A sprite may be set to 'boundary'. This is a 'normal' sprite with the exception that pen
		number 'F' is transparent (and still collideable). */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				if (color != 0x0f)
				{
					back = lynx_read_ram(screen);
					lynx_write_ram(screen, (back & 0x0f) | (color << 4));
					m_blitter.memory_accesses++;
				}
				if(m_blitter.sprite_collide && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					if ((back >> 4) > m_blitter.fred)
						m_blitter.fred = back >> 4;
					m_blitter.memory_accesses += 2;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				if (color != 0x0f)
				{
					back = lynx_read_ram(screen);
					lynx_write_ram(screen, (back & 0xf0) | color);
				}
				if(m_blitter.sprite_collide && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
					if ((back & 0x0f) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
			}
			break;

		case SHADOW:
		/* A sprite may be set to 'shadow'. This is a 'normal' sprite with the exception that pen
		number 'E' is non-collideable (but still opaque) */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0x0f) | (color << 4));
				m_blitter.memory_accesses++;

				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					if ((back >> 4) > m_blitter.fred)
						m_blitter.fred = back >> 4;
					m_blitter.memory_accesses += 2;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0xf0) | color);

				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
					if ((back & 0x0f) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
			}
			break;

		case BOUNDARY_SHADOW:
		/* This sprite is a 'normal' sprite with the characteristics of both 'boundary'
		and 'shadow'. That is, pen number 'F' is transparent (and still collideable) and
		pen number 'E' is non-collideable (but still opaque). */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				if (color != 0x0f)
				{
					back = lynx_read_ram(screen);
					lynx_write_ram(screen, (back & 0x0f) | (color << 4));
					m_blitter.memory_accesses++;
				}
				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					if ((back >> 4) > m_blitter.fred)
						m_blitter.fred = back >> 4;
					m_blitter.memory_accesses += 2;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				if (color != 0x0f)
				{
					back = lynx_read_ram(screen);
					lynx_write_ram(screen, (back & 0xf0) | color);
				}
				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
					if ((back & 0x0f) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
			}
			break;

		case BACKGROUND:
		/* A sprite may be set to 'background'. This sprite will overwrite the contents of the video and
		collision buffers. Pens '0' and 'F' are no longer transparent. This sprite is used to initialize
		the buffers at the start of a 'painting'. Additionally, no collision detection is done, and no write
		to the collision depository occurs. The 'E' error will cause the pen number 'E' to be non-collideable
		and therefore not clear the collision buffer */
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0x0f) | (color << 4));
				m_blitter.memory_accesses++;

				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					m_blitter.memory_accesses++;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0xf0) | color);

				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
				}
			}
			break;

		case BACKGROUND_NO_COLL:
		/* This is a 'background' sprite with the exception that no activity occurs in the collision buffer */
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0x0f) | (color << 4));
				m_blitter.memory_accesses++;
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0xf0) | color);
			}
			break;

		case NO_COLL:
		/* A sprite may be set to 'non-collideable'. This means that it will have no affect on the contents of
		the collision buffer and all other collision activities are overridden (pen 'F' is not collideable). */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0x0f) | (color << 4));
				m_blitter.memory_accesses++;
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, (back & 0xf0) | color);
			}
			break;

		case XOR_SPRITE:
		/* This is a 'normal' sprite with the exception that the data from the video buffer is exclusive-ored
		with the sprite data and written back out to the video buffer. Collision activity is 'normal'. The 'E'
		error will cause the pen number 'E' to be non-collideable and therefore not react with the collision
		buffer */
			if (color == 0)
				break;
			if (!(x & 0x01))        /* Upper nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, back^(color << 4));
				m_blitter.memory_accesses += 2;
				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0xf0) | (m_blitter.spritenr << 4));
					if ((back >> 4) > m_blitter.fred)
						m_blitter.fred = back >> 4;
					m_blitter.memory_accesses += 2;
				}
				m_blitter.memory_accesses++;
			}
			else                    /* Lower nibble */
			{
				back = lynx_read_ram(screen);
				lynx_write_ram(screen, back^color);
				if (m_blitter.sprite_collide && (color != 0x0e) && !(m_blitter.no_collide))
				{
					back = lynx_read_ram(colbuf);
					lynx_write_ram(colbuf, (back & ~0x0f) | (m_blitter.spritenr));
					if ((back & 0x0f) > m_blitter.fred)
						m_blitter.fred = back >> 4;
				}
			}
			break;
	}
}

void lynx_state::lynx_blit_do_work( const int y, const int xdir, const int bits_per_pixel, const int mask )
{
	int next_line_addr,i,j;
	int xi, bits, color;
	uint16_t width_accum, buffer;

	next_line_addr = lynx_read_ram(m_blitter.bitmap); // offset to second sprite line
	width_accum = (xdir == 1) ? m_blitter.width_offset : 0;
	m_blitter.memory_accesses++;

	for (xi = m_blitter.x_pos - m_blitter.xoff, bits = 0, buffer = 0, j = 1; j < next_line_addr;j++)
	{
		buffer = (buffer << 8) | lynx_read_ram(m_blitter.bitmap + j);
		bits += 8; // current bits in buffer
		m_blitter.memory_accesses++;

		for ( ; bits > bits_per_pixel; bits -= bits_per_pixel) // last data packet at end of scanline is not rendered (qix, blulght)
		{
			color = m_blitter.color[(buffer >> (bits - bits_per_pixel)) & mask];
			width_accum += m_blitter.width;
			for (i = 0; i < (width_accum>>8); i++, xi += xdir)
			{
				if ((xi >= 0) && (xi < 160))
				{
					lynx_plot_pixel(m_blitter.mode, xi, y, color);
				}
			}
			width_accum &= 0xff;
		}
	}
}

void lynx_state::lynx_blit_rle_do_work( const int16_t y, const int xdir, const int bits_per_pixel, const int mask )
{
	int i;
	int xi;
	int buffer, bits, j;
	int literal_data, count, color;
	uint16_t width_accum;

	width_accum = (xdir == 1) ? m_blitter.width_offset : 0;
	for( bits = 0, j = 0, buffer = 0, xi = m_blitter.x_pos - m_blitter.xoff; ; )      /* through the rle entries */
	{
		if (bits < 5 + bits_per_pixel) /* under 7 bits no complete entry */
		{
			j++;
			if (j >= lynx_read_ram(m_blitter.bitmap))
				return;

			bits += 8;
			buffer = (buffer << 8) | lynx_read_ram(m_blitter.bitmap + j);
			m_blitter.memory_accesses++;
		}

		literal_data = (buffer >> (bits - 1)) & 0x01;
		bits--;
		count = (buffer >> (bits - 4)) & 0x0f; // repeat count (packed) or pixel count (literal)
		bits -= 4;

		if (literal_data)       /* count of different pixels */
		{
			for ( ; count >= 0; count--)
			{
				if (bits < bits_per_pixel)
				{
					j++;
					if (j >= lynx_read_ram(m_blitter.bitmap))
						return;
					bits += 8;
					buffer = (buffer << 8) | lynx_read_ram(m_blitter.bitmap + j);
					m_blitter.memory_accesses++;
				}

				color = m_blitter.color[(buffer >> (bits - bits_per_pixel)) & mask];
				bits -= bits_per_pixel;
				width_accum += m_blitter.width;
				for (i = 0; i < (width_accum>>8); i++, xi += xdir)
				{
					if ((xi >= 0) && (xi < 160))
						lynx_plot_pixel(m_blitter.mode, xi, y, color);
				}
				width_accum &= 0xff;
			}
		}
		else        /* count of same pixels */
		{
			if (count == 0) // 4 bit count value of zero indicates end-of-line in a packed sprite
				return;

			if (bits < bits_per_pixel)
			{
				j++;
				if (j >= lynx_read_ram(m_blitter.bitmap))
					return;
				bits += 8;
				buffer = (buffer << 8) | lynx_read_ram(m_blitter.bitmap + j);
				m_blitter.memory_accesses++;
			}

			color = m_blitter.color[(buffer >> (bits - bits_per_pixel)) & mask];
			bits -= bits_per_pixel;

			for ( ; count>=0; count--)
			{
				width_accum += m_blitter.width;
				for (i = 0; i < (width_accum >> 8); i++, xi += xdir)
				{
					if ((xi >= 0) && (xi < 160))
						lynx_plot_pixel(m_blitter.mode, xi, y, color);
				}
				width_accum &= 0xff;
			}
		}
	}
}

void lynx_state::lynx_blit_lines()
{
	static const int lynx_color_masks[4] = { 0x01, 0x03, 0x07, 0x0f };
	int16_t y;
	int i;
	int ydir = 0, xdir = 0;
	int flip = 0;

	m_blitter.everon = false;

	switch (m_blitter.spr_ctl1 & 0x03)   /* Initial drawing direction */
	{
		case 0: // Down/Right (quadrant 0)
			xdir = 1;
			ydir = 1;
			flip = 0;
			break;
		case 1: // Down/Left (blockout) (quadrant 3)
			xdir = -1;
			ydir = 1;
			flip = 3;
			break;
		case 2: // Up/Right (fat bobby) (quadrant 1)
			xdir = 1;
			ydir = -1;
			flip = 1;
			break;
		case 3: // Up/Left (quadrant 2)
			xdir = -1;
			ydir = -1;
			flip = 2;
			break;
	}

	if (m_blitter.spr_ctl0 & 0x20)   /* Horizontal Flip */
	{
		xdir *= -1;
	}

	if (m_blitter.spr_ctl0 & 0x10)   /* Vertical Flip */
	{
		ydir *= -1;
	}

	// Set height accumulator based on drawing direction
	m_blitter.height_accumulator = (ydir == 1) ? m_blitter.height_offset : 0x00;

	// loop through lines, next line offset of zero indicates end of sprite
	for (y = m_blitter.y_pos - m_blitter.yoff; (i = lynx_read_ram(m_blitter.bitmap)); m_blitter.bitmap += i)
	{
		m_blitter.memory_accesses++;

		if (i == 1) // draw next quadrant
		{
			// centered sprites sprdemo3, fat bobby, blockout
			switch (flip & 0x03)
			{
				case 0:
				case 2:
					ydir *= -1;
					m_blitter.y_pos += ydir;
					break;
				case 1:
				case 3:
					xdir *= -1;
					m_blitter.x_pos += xdir;
					break;
			}
			flip++;
			y = m_blitter.y_pos - m_blitter.yoff;
			m_blitter.height_accumulator = (ydir == 1) ? m_blitter.height_offset : 0x00;
			continue;
		}

		m_blitter.height_accumulator += m_blitter.height;
		for (int j = 0; j < (m_blitter.height_accumulator >> 8); j++, y += ydir)
		{
			if (y >= 0 && y < 102)
			{
				if (m_blitter.use_rle)
					lynx_blit_rle_do_work(y, xdir, m_blitter.line_color + 1, lynx_color_masks[m_blitter.line_color]);
				else
					lynx_blit_do_work(y, xdir, m_blitter.line_color + 1, lynx_color_masks[m_blitter.line_color]);
			}
			m_blitter.width += (int16_t)m_blitter.stretch;
			if (m_blitter.vstretch) // doesn't seem to be used
			{
				m_blitter.height += (int16_t)m_blitter.stretch;
				logerror("vertical stretch enabled");
			}
			m_blitter.tilt_accumulator += m_blitter.tilt;
			m_blitter.x_pos += (m_blitter.tilt_accumulator>>8);
			m_blitter.tilt_accumulator &= 0xff;
		}
		m_blitter.height_accumulator &= 0xff;
	}
}

void lynx_state::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
	switch (id)
	{
	case TIMER_BLITTER:
		lynx_blitter_timer(ptr, param);
		break;
	case TIMER_SHOT:
		lynx_timer_shot(ptr, param);
		break;
	case TIMER_UART_LOOPBACK:
		lynx_uart_loopback_timer(ptr, param);
		break;
	case TIMER_UART:
		lynx_uart_timer(ptr, param);
		break;
	default:
		assert_always(false, "Unknown id in lynx_state::device_timer");
	}
}

TIMER_CALLBACK_MEMBER(lynx_state::lynx_blitter_timer)
{
	m_blitter.busy=0; // blitter finished
	m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
}

/*
  control 0
   bit 7,6: 00 2 color
            01 4 color
            11 8 colors?
            11 16 color
   bit 5,4: 00 right down
            01 right up
            10 left down
            11 left up

#define SHADOW         (0x07)
#define XORSHADOW      (0x06)
#define NONCOLLIDABLE  (0x05)
#define NORMAL         (0x04)
#define BOUNDARY       (0x03)
#define BOUNDARYSHADOW (0x02)
#define BKGRNDNOCOL    (0x01)
#define BKGRND         (0x00)

  control 1
   bit 7: 0 bitmap rle encoded
          1 not encoded
   bit 3: 0 color info with command
          1 no color info with command

#define RELHVST        (0x30)
#define RELHVS         (0x20)
#define RELHV          (0x10)

#define SKIPSPRITE     (0x04)

#define DUP            (0x02)
#define DDOWN          (0x00)
#define DLEFT          (0x01)
#define DRIGHT         (0x00)


  coll
#define DONTCOLLIDE    (0x20)

  word next
  word data
  word x
  word y
  word width
  word height

  pixel c0 90 20 0000 datapointer x y 0100 0100 color (8 colorbytes)
  4 bit direct?
  datapointer 2 10 0
  98 (0 colorbytes)

  box c0 90 20 0000 datapointer x y width height color
  datapointer 2 10 0

  c1 98 00 4 bit direct without color bytes (raycast)

  40 10 20 4 bit rle (sprdemo2)

  line c1 b0 20 0000 datapointer x y 0100 0100 stretch tilt:x/y color (8 color bytes)
  or
  line c0 b0 20 0000 datapointer x y 0100 0100 stretch tilt:x/y color
  datapointer 2 11 0

  text ?(04) 90 20 0000 datapointer x y width height color
  datapointer 2 10 0

  stretch: hsize adder
  tilt: hpos adder

*/

void lynx_state::lynx_blitter()
{
	static const int lynx_colors[4] = { 2, 4, 8, 16 };
	uint8_t palette_offset;
	uint8_t coldep;
	int colors;

	m_blitter.busy = 1; // blitter working
	m_blitter.memory_accesses = 0;

	// Last SCB is indicated by zero in the high byte of SCBNEXT
	while (m_blitter.scb_next & 0xff00)
	{
		m_blitter.stretch = 0;
		m_blitter.tilt    = 0;
		m_blitter.tilt_accumulator = 0;

		m_blitter.scb = m_blitter.scb_next; // current scb
		m_blitter.scb_next = lynx_read_ram(m_blitter.scb + SCB_SCBNEXT) | (lynx_read_ram(m_blitter.scb + SCB_SCBNEXT + 1) << 8); // next scb
		m_blitter.spr_ctl0 = lynx_read_ram(m_blitter.scb + SCB_SPRCTL0);
		m_blitter.spr_ctl1 = lynx_read_ram(m_blitter.scb + SCB_SPRCTL1);
		m_blitter.spr_coll = lynx_read_ram(m_blitter.scb + SCB_SPRCOLL);
		m_blitter.memory_accesses += 5;

		if(!(m_blitter.spr_ctl1 & 0x04)) // sprite will be processed (if sprite is skipped first 5 bytes are still copied to suzy)
		{
			m_blitter.bitmap = lynx_read_ram(m_blitter.scb + SCB_SPRDLINE) | (lynx_read_ram(m_blitter.scb + SCB_SPRDLINE + 1) << 8);
			m_blitter.x_pos = lynx_read_ram(m_blitter.scb + SCB_HPOSSTRT) | (lynx_read_ram(m_blitter.scb + SCB_HPOSSTRT + 1) << 8);
			m_blitter.y_pos = lynx_read_ram(m_blitter.scb + SCB_VPOSSTRT) | (lynx_read_ram(m_blitter.scb + SCB_VPOSSTRT + 1) << 8);
			m_blitter.memory_accesses += 6;

			switch(m_blitter.spr_ctl1 & 0x30) // reload sprite scaling
			{
				case 0x30: // width, height, tilt, stretch
					m_blitter.tilt = lynx_read_ram(m_blitter.scb + SCB_TILT) | (lynx_read_ram(m_blitter.scb + SCB_TILT + 1) << 8);
					m_blitter.memory_accesses+=2;
				case 0x20: // width, height, stretch
					m_blitter.stretch = lynx_read_ram(m_blitter.scb + SCB_STRETCH) | (lynx_read_ram(m_blitter.scb + SCB_STRETCH + 1) << 8);
					m_blitter.memory_accesses+=2;
				case 0x10: // width, height
					m_blitter.width = lynx_read_ram(m_blitter.scb + SCB_SPRHSIZ) | (lynx_read_ram(m_blitter.scb + SCB_SPRHSIZ + 1) << 8);
					m_blitter.height = lynx_read_ram(m_blitter.scb + SCB_SPRVSIZ) | (lynx_read_ram(m_blitter.scb + SCB_SPRVSIZ + 1) << 8);
					m_blitter.memory_accesses+=4;
			}

			if(!(m_blitter.spr_ctl1 & 0x08)) // reload palette
			{
				if (m_blitter.spr_ctl1 & 0x30)
					palette_offset = 0x0b + 2*(((m_blitter.spr_ctl1 & 0x30)>>4) + 1); // palette data offset depends on width, height, etc. reloading
				else
					palette_offset = 0x0b;

				colors = lynx_colors[m_blitter.spr_ctl0 >> 6];

				for (int i = 0; i < colors / 2; i++)
				{
					m_blitter.color[i * 2]      = lynx_read_ram(m_blitter.scb + palette_offset + i) >> 4;
					m_blitter.color[i * 2 + 1 ] = lynx_read_ram(m_blitter.scb + palette_offset + i) & 0x0f;
					m_blitter.memory_accesses++;
				}
			}
			}


		if (!(m_blitter.spr_ctl1 & 0x04))        // if 0, we skip this sprite
		{
			m_blitter.colpos = m_blitter.scb + (m_suzy.data[COLLOFFL] | (m_suzy.data[COLLOFFH]<<8));
			m_blitter.mode = m_blitter.spr_ctl0 & 0x07;
			m_blitter.use_rle = m_blitter.spr_ctl1 & 0x80 ? 0 : 1;
			m_blitter.line_color = (m_blitter.spr_ctl0 >> 6) & 0x03;

			m_blitter.sprite_collide = !(m_blitter.spr_coll & 0x20);
			m_blitter.spritenr = m_blitter.spr_coll & 0x0f;
			m_blitter.fred = 0;

			/* Draw Sprite */
			lynx_blit_lines();

			if (m_blitter.sprite_collide && !(m_blitter.no_collide))
			{
				switch (m_blitter.mode)
				{
					case BOUNDARY_SHADOW:
					case BOUNDARY:
					case NORMAL_SPRITE:
					case XOR_SPRITE:
					case SHADOW:
						lynx_write_ram(m_blitter.colpos, m_blitter.fred);
						break;
				}
			}

			if (m_suzy.data[SPRGO] & 0x04) // Everon enabled
			{
				coldep = lynx_read_ram(m_blitter.colpos);
				if (!m_blitter.everon)
					coldep |= 0x80;
				else
					coldep &= 0x7f;
				lynx_write_ram(m_blitter.colpos, coldep);
			}
		}
	}

	timer_set(m_maincpu->cycles_to_attotime(m_blitter.memory_accesses), TIMER_BLITTER);
}


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

    Suzy Emulation

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


/* Math bugs of the original hardware:

- in signed multiply, the hardware thinks that 8000 is a positive number
- in signed multiply, the hardware thinks that 0 is a negative number. This is not an immediate
problem for a multiply by zero, since the answer will be re-negated to the correct polarity of
zero. However, since it will set the sign flag, you can not depend on the sign flag to be correct
if you just load the lower byte after a multiply by zero.
- in divide, the remainder will have 2 possible errors, depending on its actual value (no further
notes on these errors available) */

void lynx_state::lynx_divide()
{
	uint32_t left;
	uint16_t right;
	uint32_t res, mod;
	/*
	Hardware divide:
	            EFGH
	*             NP
	----------------
	            ABCD
	Remainder (JK)LM
	*/

	left = m_suzy.data[MATH_H] | (m_suzy.data[MATH_G] << 8) | (m_suzy.data[MATH_F] << 16) | (m_suzy.data[MATH_E] << 24);
	right = m_suzy.data[MATH_P] | (m_suzy.data[MATH_N] << 8);

	m_suzy.accumulate_overflow = false;
	if (right == 0)
	{
		m_suzy.accumulate_overflow = true;  /* during divisions, this bit is used to detect denominator = 0 */
		res = 0xffffffff;
		mod = 0; //?
	}
	else
	{
		res = left / right;
		mod = left % right;
	}
//  logerror("coprocessor %8x / %8x = %4x\n", left, right, res);
	m_suzy.data[MATH_D] = res & 0xff;
	m_suzy.data[MATH_C] = res >> 8;
	m_suzy.data[MATH_B] = res >> 16;
	m_suzy.data[MATH_A] = res >> 24;

	m_suzy.data[MATH_M] = mod & 0xff;
	m_suzy.data[MATH_L] = mod >> 8;
	m_suzy.data[MATH_K] = 0; // documentation states the hardware sets these to zero on divides
	m_suzy.data[MATH_J] = 0;
}

void lynx_state::lynx_multiply()
{
	uint16_t left, right;
	uint32_t res, accu;
	/*
	Hardware multiply:
	              AB
	*             CD
	----------------
	            EFGH
	Accumulate  JKLM
	*/
	m_suzy.accumulate_overflow = false;

	left = m_suzy.data[MATH_B] | (m_suzy.data[MATH_A] << 8);
	right = m_suzy.data[MATH_D] | (m_suzy.data[MATH_C] << 8);

	res = left * right;

	if (m_suzy.signed_math)
	{
		if (!(m_sign_AB + m_sign_CD))   /* different signs */
			res = (res ^ 0xffffffff) + 1;
	}

	m_suzy.data[MATH_H] = res & 0xff;
	m_suzy.data[MATH_G] = res >> 8;
	m_suzy.data[MATH_F] = res >> 16;
	m_suzy.data[MATH_E] = res >> 24;

	if (m_suzy.accumulate)
	{
		accu = m_suzy.data[MATH_M] | m_suzy.data[MATH_L] << 8 | m_suzy.data[MATH_K] << 16 | m_suzy.data[MATH_J] << 24;
		accu += res;

		if (accu < res)
			m_suzy.accumulate_overflow = true;

		m_suzy.data[MATH_M] = accu;
		m_suzy.data[MATH_L] = accu >> 8;
		m_suzy.data[MATH_K] = accu >> 16;
		m_suzy.data[MATH_J] = accu >> 24;
	}
}

READ8_MEMBER(lynx_state::suzy_read)
{
	uint8_t value = 0, input;

	switch (offset)
	{
		case TILTACUML:
			return m_blitter.tilt_accumulator & 0xff;
		case TILTACUMH:
			return m_blitter.tilt_accumulator>>8;
		case HOFFL:
			return m_blitter.xoff & 0xff;
		case HOFFH:
			return m_blitter.xoff>>8;
		case VOFFL:
			return m_blitter.yoff & 0xff;
		case VOFFH:
			return m_blitter.yoff>>8;
		case VIDBASL:
			return m_blitter.screen & 0xff;
		case VIDBASH:
			return m_blitter.screen>>8;
		case COLLBASL:
			return m_blitter.colbuf & 0xff;
		case COLLBASH:
			return m_blitter.colbuf>>8;
		case SCBNEXTL:
			return m_blitter.scb_next & 0xff;
		case SCBNEXTH:
			return m_blitter.scb_next>>8;
		case SPRDLINEL:
			return m_blitter.bitmap & 0xff;
		case SPRDLINEH:
			return m_blitter.bitmap>>8;
		case HPOSSTRTL:
			return m_blitter.x_pos & 0xff;
		case HPOSSTRTH:
			return m_blitter.x_pos>>8;
		case VPOSSTRTL:
			return m_blitter.y_pos & 0xff;
		case VPOSSTRTH:
			return m_blitter.y_pos>>8;
		case SPRHSIZL:
			return m_blitter.width & 0xff;
		case SPRHSIZH:
			return m_blitter.width>>8;
		case SPRVSIZL:
			return m_blitter.height & 0xff;
		case SPRVSIZH:
			return m_blitter.height>>8;
		case STRETCHL:
			return m_blitter.stretch & 0xff;
		case STRETCHH:
			return m_blitter.stretch>>8;
		case TILTL:
			return m_blitter.tilt & 0xff;
		case TILTH:
			return m_blitter.tilt>>8;
		// case SPRDOFFL:
		// case SPRVPOSL:
		// case COLLOFFL:
		case VSIZACUML:
			return m_blitter.height_accumulator & 0xff;
		case VSIZACUMH:
			return m_blitter.height_accumulator>>8;
		case HSIZOFFL:
			return m_blitter.width_offset & 0xff;
		case HSIZOFFH:
			return m_blitter.width_offset>>8;
		case VSIZOFFL:
			return m_blitter.height_offset & 0xff;
		case VSIZOFFH:
			return m_blitter.height_offset>>8;
		case SCBADRL:
			return m_blitter.scb & 0xff;
		case SCBADRH:
			return m_blitter.scb>>8;
		//case PROCADRL:
		case SUZYHREV:
			return 0x01; // must not be 0 for correct power up
		case SPRSYS:
			// math busy, last carry, unsafe access, and stop on current sprite bits not implemented.
			if (m_suzy.accumulate_overflow)
				value |= 0x40;
			if (m_blitter.vstretch)
				value |= 0x10;
			if (m_blitter.lefthanded)
				value |= 0x08;
			if (m_blitter.busy)
				value |= 0x01;
			break;
		case JOYSTICK:
			input = ioport("JOY")->read();
			switch (m_rotate)
			{
				case 1:
					value = input;
					input &= 0x0f;
					if (value & PAD_UP) input |= PAD_LEFT;
					if (value & PAD_LEFT) input |= PAD_DOWN;
					if (value & PAD_DOWN) input |= PAD_RIGHT;
					if (value & PAD_RIGHT) input |= PAD_UP;
					break;
				case 2:
					value = input;
					input &= 0x0f;
					if (value & PAD_UP) input |= PAD_RIGHT;
					if (value & PAD_RIGHT) input |= PAD_DOWN;
					if (value & PAD_DOWN) input |= PAD_LEFT;
					if (value & PAD_LEFT) input |= PAD_UP;
					break;
			}
			if (m_blitter.lefthanded)
			{
				value = input & 0x0f;
				if (input & PAD_UP) value |= PAD_DOWN;
				if (input & PAD_DOWN) value |= PAD_UP;
				if (input & PAD_LEFT) value |= PAD_RIGHT;
				if (input & PAD_RIGHT) value |= PAD_LEFT;
			}
			else
				value = input;
			break;
		case SWITCHES:
			value = ioport("PAUSE")->read();
			break;
		case RCART:
			if (m_cart->exists())
				value = m_cart->read_rom(space, (m_suzy.high * m_granularity) + m_suzy.low);
			else
				value = 0;
			m_suzy.low = (m_suzy.low + 1) & (m_granularity - 1);
			break;
		//case RCART_BANK1: /* we need bank 1 emulation!!! */
		case SPRCTL0:
		case SPRCTL1:
		case SPRCOLL:
		case SPRINIT:
		case SUZYBUSEN:
		case SPRGO:
			logerror("read from write only register %x\n", offset);
			value = 0;
			break;
		default:
			value = m_suzy.data[offset];
	}
	//logerror("suzy read %.2x %.2x\n",offset,value);
	return value;
}

WRITE8_MEMBER(lynx_state::suzy_write)
{
	m_suzy.data[offset] = data;
	//logerror("suzy write %.2x %.2x\n",offset,data);
	/* Additional effects of a write */
	/* Even addresses are the LSB. Any CPU write to an LSB in 0x00-0x7f will set the MSB to 0. */
	/* This in particular holds for math quantities:  Writing to B (0x54), D (0x52),
	F (0x62), H (0x60), K (0x6e) or M (0x6c) will force a '0' to be written to A (0x55),
	C (0x53), E (0x63), G (0x61), J (0x6f) or L (0x6d) respectively */
	if ((offset < 0x80) && !(offset & 0x01))
	m_suzy.data[offset + 1] = 0;

	switch(offset)
	{
		//case TMPADRL:
		//case TMPADRH:
		case TILTACUML:
			m_blitter.tilt_accumulator = data; // upper byte forced to zero see above.
			break;
		case TILTACUMH:
			m_blitter.tilt_accumulator &= 0xff;
			m_blitter.tilt_accumulator |= data<<8;
			break;
		case HOFFL:
			m_blitter.xoff = data;
			break;
		case HOFFH:
			m_blitter.xoff &= 0xff;
			m_blitter.xoff |= data<<8;
			break;
		case VOFFL:
			m_blitter.yoff = data;
			break;
		case VOFFH:
			m_blitter.yoff &= 0xff;
			m_blitter.yoff |= data<<8;
			break;
		case VIDBASL:
			m_blitter.screen = data;
			break;
		case VIDBASH:
			m_blitter.screen &= 0xff;
			m_blitter.screen |= data<<8;
			break;
		case COLLBASL:
			m_blitter.colbuf = data;
			break;
		case COLLBASH:
			m_blitter.colbuf &= 0xff;
			m_blitter.colbuf |= data<<8;
			break;
		case SCBNEXTL:
			m_blitter.scb_next = data;
			break;
		case SCBNEXTH:
			m_blitter.scb_next &= 0xff;
			m_blitter.scb_next |= data<<8;
			break;
		case SPRDLINEL:
			m_blitter.bitmap = data;
			break;
		case SPRDLINEH:
			m_blitter.bitmap &= 0xff;
			m_blitter.bitmap |= data<<8;
			break;
		case HPOSSTRTL:
			m_blitter.x_pos = data;
		case HPOSSTRTH:
			m_blitter.x_pos &= 0xff;
			m_blitter.x_pos |= data<<8;
		case VPOSSTRTL:
			m_blitter.y_pos = data;
		case VPOSSTRTH:
			m_blitter.y_pos &= 0xff;
			m_blitter.y_pos |= data<<8;
		case SPRHSIZL:
			m_blitter.width = data;
			break;
		case SPRHSIZH:
			m_blitter.width &= 0xff;
			m_blitter.width |= data<<8;
			break;
		case SPRVSIZL:
			m_blitter.height = data;
			break;
		case SPRVSIZH:
			m_blitter.height &= 0xff;
			m_blitter.height |= data<<8;
			break;
		case STRETCHL:
			m_blitter.stretch = data;
			break;
		case STRETCHH:
			m_blitter.stretch &= 0xff;
			m_blitter.stretch |= data<<8;
			break;
		case TILTL:
			m_blitter.tilt = data;
			break;
		case TILTH:
			m_blitter.tilt &= 0xff;
			m_blitter.tilt |= data<<8;
			break;
		// case SPRDOFFL:
		// case SPRVPOSL:
		// case COLLOFFL:
		case VSIZACUML:
			m_blitter.height_accumulator = data;
			break;
		case VSIZACUMH:
			m_blitter.height_accumulator &= 0xff;
			m_blitter.height_accumulator |= data<<8;
			break;
		case HSIZOFFL:
			m_blitter.width_offset = data;
			break;
		case HSIZOFFH:
			m_blitter.width_offset &= 0xff;
			m_blitter.width_offset |= data<<8;
			break;
		case VSIZOFFL:
			m_blitter.height_offset = data;
			break;
		case VSIZOFFH:
			m_blitter.height_offset &= 0xff;
			m_blitter.height_offset |= data<<8;
			break;
		case SCBADRL:
			m_blitter.scb = data;
			break;
		case SCBADRH:
			m_blitter.scb &= 0xff;
			m_blitter.scb |= data<<8;
			break;
		//case PROCADRL:

		/* Writing to M (0x6c) will also clear the accumulator overflow bit */
		case MATH_M:
			m_suzy.accumulate_overflow = false;
			break;
		case MATH_C:
			/* If we are going to perform a signed multiplication, we store the sign and convert the number
			to an unsigned one */
			if (m_suzy.signed_math)
			{
				uint16_t factor, temp;
				factor = m_suzy.data[MATH_D] | (m_suzy.data[MATH_C] << 8);
				if ((factor - 1) & 0x8000)      /* here we use -1 to cover the math bugs on the sign of 0 and 0x8000 */
				{
					temp = (factor ^ 0xffff) + 1;
					m_sign_CD = - 1;
					m_suzy.data[MATH_D] = temp & 0xff;
					m_suzy.data[MATH_C] = temp >> 8;
				}
				else
					m_sign_CD = 1;
			}
			break;
		case MATH_D:
		/* Documentation states that writing to the MATH_D will set MATH_C to zero but not update the sign flag.
		Implementing the sign detection as described in the documentation causes Stun Runners to not work.
		Either the sign error in the docs is not as described or writing to the lower byte does update the sign flag.
		Here I assume the sign flag gets updated. */
			if (data)
				m_sign_CD = 1;
			break;
		/* Writing to A will start a 16 bit multiply */
		/* If we are going to perform a signed multiplication, we also store the sign and convert the
		number to an unsigned one */
		case MATH_A:
			if (m_suzy.signed_math)
			{
				uint16_t factor, temp;
				factor = m_suzy.data[MATH_B] | (m_suzy.data[MATH_A] << 8);
				if ((factor - 1) & 0x8000)      /* here we use -1 to cover the math bugs on the sign of 0 and 0x8000 */
				{
					temp = (factor ^ 0xffff) + 1;
					m_sign_AB = - 1;
					m_suzy.data[MATH_B] = temp & 0xff;
					m_suzy.data[MATH_A] = temp >> 8;
				}
				else
					m_sign_AB = 1;
			}
			lynx_multiply();
			break;
		/* Writing to E will start a 16 bit divide */
		case MATH_E:
			lynx_divide();
			break;
		case SPRCTL0:
			m_blitter.spr_ctl0 = data;
			break;
		case SPRCTL1:
			m_blitter.spr_ctl1 = data;
			break;
		case SPRCOLL:
			m_blitter.spr_coll = data;
			break;
		case SUZYBUSEN:
			logerror("write to SUSYBUSEN %x \n", data);
			break;
		case SPRSYS:
				m_suzy.signed_math = (data & 0x80) ? 1:0;
				m_suzy.accumulate = (data & 0x40) ? 1:0;
				m_blitter.no_collide = (data & 0x20) ? 1:0;
				m_blitter.vstretch = (data & 0x10) ? 1:0;
				m_blitter.lefthanded = (data & 0x08) ? 1:0;
				// unsafe access clear and sprite engine stop request are not enabled
				if (data & 0x02) logerror("sprite engine stop request\n");
				break;
		case SPRGO:
			if ((data & 0x01) && m_suzy.data[SUZYBUSEN])
			{
				//m_blitter.time = machine().time();
				lynx_blitter();
			}
			break;
		case JOYSTICK:
		case SWITCHES:
			logerror("warning: write to read-only button registers\n");
			break;
	}
}


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

    Mikey emulation

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

/*
 0xfd0a r sync signal?
 0xfd81 r interrupt source bit 2 vertical refresh
 0xfd80 w interrupt quit
 0xfd87 w bit 1 !clr bit 0 blocknumber clk
 0xfd8b w bit 1 blocknumber hi B
 0xfd94 w 0
 0xfd95 w 4
 0xfda0-f rw farben 0..15
 0xfdb0-f rw bit0..3 farben 0..15
*/


/*
DISPCTL EQU $FD92       ; set to $D by INITMIKEY

; B7..B4        0
; B3    1 EQU color
; B2    1 EQU 4 bit mode
; B1    1 EQU flip screen
; B0    1 EQU video DMA enabled
*/

void lynx_state::lynx_draw_line()
{
	int x, y;
	uint16_t j; // clipping needed!
	uint8_t byte;
	uint16_t *line;


	// calculate y: first three lines are vblank,
	y = 101-m_timer[2].counter;
	// Documentation states lower two bits of buffer address are ignored (thus 0xfffc mask)
	j = (m_mikey.disp_addr & 0xfffc) + y * 160 / 2;

	if (m_mikey.data[0x92] & 0x02)
	{
		j -= 160 * 102 / 2 - 1;
		line = &m_bitmap_temp.pix16(102 - 1 - y);
		for (x = 160 - 2; x >= 0; j++, x -= 2)
		{
			byte = lynx_read_ram(j);
			line[x + 1] = m_lynx_palette[(byte >> 4) & 0x0f];
			line[x + 0] = m_lynx_palette[(byte >> 0) & 0x0f];
		}
	}
	else
	{
		line = &m_bitmap_temp.pix16(y);
		for (x = 0; x < 160; j++, x += 2)
		{
			byte = lynx_read_ram(j);
			line[x + 0] = m_lynx_palette[(byte >> 4) & 0x0f];
			line[x + 1] = m_lynx_palette[(byte >> 0) & 0x0f];
		}
	}
}

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

    Timers

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

/*
HCOUNTER        EQU TIMER0
VCOUNTER        EQU TIMER2
SERIALRATE      EQU TIMER4

TIM_BAKUP       EQU 0   ; backup-value (count+1)
TIM_CNTRL1      EQU 1   ; timer-control register
TIM_CNT EQU 2   ; current counter
TIM_CNTRL2      EQU 3   ; dynamic control

; TIM_CNTRL1
TIM_IRQ EQU %10000000   ; enable interrupt (not TIMER4 !)
TIM_RESETDONE   EQU %01000000   ; reset timer done
TIM_MAGMODE     EQU %00100000   ; nonsense in Lynx !!
TIM_RELOAD      EQU %00010000   ; enable reload
TIM_COUNT       EQU %00001000   ; enable counter
TIM_LINK        EQU %00000111
; link timers (0->2->4 / 1->3->5->7->Aud0->Aud1->Aud2->Aud3->1
TIM_64us        EQU %00000110
TIM_32us        EQU %00000101
TIM_16us        EQU %00000100
TIM_8us EQU %00000011
TIM_4us EQU %00000010
TIM_2us EQU %00000001
TIM_1us EQU %00000000

;TIM_CNTRL2 (read-only)
; B7..B4 unused
TIM_DONE        EQU %00001000   ; set if timer's done; reset with TIM_RESETDONE
TIM_LAST        EQU %00000100   ; last clock (??)
TIM_BORROWIN    EQU %00000010
TIM_BORROWOUT   EQU %00000001
*/

#define NR_LYNX_TIMERS  8




void lynx_state::lynx_timer_init(int which)
{
	memset(&m_timer[which], 0, sizeof(LYNX_TIMER));
	m_timer[which].timer = timer_alloc(TIMER_SHOT);

	save_item(NAME(m_timer[which].bakup), which);
	save_item(NAME(m_timer[which].cntrl1), which);
	save_item(NAME(m_timer[which].cntrl2), which);
	save_item(NAME(m_timer[which].counter), which);
	save_item(NAME(m_timer[which].timer_active), which);
}

void lynx_state::lynx_timer_signal_irq(int which)
{
	if ((m_timer[which].cntrl1 & 0x80) && (which != 4)) // if interrupts are enabled and timer != 4
	{
		m_mikey.data[0x81] |= (1 << which); // set interrupt poll register
		m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
		m_maincpu->set_input_line(M65SC02_IRQ_LINE, ASSERT_LINE);
	}
	switch (which) // count down linked timers
	{
	case 0:
		switch (m_timer[2].counter)
		{
			case 104:
				break;
			case 103:
				m_mikey.vb_rest = 1;
				break;
			case 102:
				m_mikey.disp_addr = m_mikey.data[0x94] | (m_mikey.data[0x95] << 8);
				break;
			case 101:
				m_mikey.vb_rest = 0;
				lynx_draw_line();
				break;
			default:
				lynx_draw_line();
		}
		lynx_timer_count_down(2);
		break;
	case 2:
		copybitmap(m_bitmap, m_bitmap_temp, 0, 0, 0, 0, machine().first_screen()->cliprect());
		lynx_timer_count_down(4);
		break;
	case 1:
		lynx_timer_count_down(3);
		break;
	case 3:
		lynx_timer_count_down(5);
		break;
	case 5:
		lynx_timer_count_down(7);
		break;
	case 7:
		m_sound->count_down(0);
		break;
	}
}

void lynx_state::lynx_timer_count_down(int which)
{
	if ((m_timer[which].cntrl1 & 0x0f) == 0x0f) // count and linking enabled
	{
		if (m_timer[which].counter > 0)
		{
			m_timer[which].counter--;
			//m_timer[which].borrow_in = 1;
			return;
		}
		if (m_timer[which].counter == 0)
		{
			if (m_timer[which].cntrl2 & 0x01) // borrow out
			{
				lynx_timer_signal_irq(which);
				if (m_timer[which].cntrl1 & 0x10) // if reload enabled
				{
					m_timer[which].counter = m_timer[which].bakup;
				}
				else
				{
					m_timer[which].cntrl2 |= 8; // set timer done
				}
				m_timer[which].cntrl2 &= ~0x01; // clear borrow out
			}
			else
				m_timer[which].cntrl2 |= 0x01; // set borrow out
			return;
		}
	}
	else
	{
		//m_timer[which].borrow_in = 0;
		m_timer[which].cntrl2 &= ~0x01;
	}
}

uint32_t lynx_state::lynx_time_factor(int val)
{
	switch(val)
	{
		case 0: return 1000000;
		case 1: return 500000;
		case 2: return 250000;
		case 3: return 125000;
		case 4: return 62500;
		case 5: return 31250;
		case 6: return 15625;
		default: fatalerror("invalid value\n");
	}
}

TIMER_CALLBACK_MEMBER(lynx_state::lynx_timer_shot)
{
	lynx_timer_signal_irq(param);
	if (!(m_timer[param].cntrl1 & 0x10)) // if reload not enabled
	{
		m_timer[param].timer_active = 0;
		m_timer[param].cntrl2 |= 8; // set timer done
	}
	else
	{
		attotime t = (attotime::from_hz(lynx_time_factor(m_timer[param].cntrl1 & 0x07)) * (m_timer[param].bakup + 1));
		m_timer[param].timer->adjust(t, param);
	}
}

uint8_t lynx_state::lynx_timer_read(int which, int offset)
{
	uint8_t value = 0;

	switch (offset)
	{
		case 0:
			value = m_timer[which].bakup;
			break;
		case 1:
			value = m_timer[which].cntrl1;
			break;
		case 2:
			if ((m_timer[which].cntrl1 & 0x07) == 0x07) // linked timer
			{
				value = m_timer[which].counter;
			}
			else
			{
				if ( m_timer[which].timer_active )
				{
					value = (uint8_t) (m_timer[which].timer->remaining().as_ticks(1000000>>(m_timer[which].cntrl1 & 0x07)));
					value -= value ? 1 : 0;
				}
			}
			break;

		case 3:
			value = m_timer[which].cntrl2;
			break;
	}
	// logerror("timer %d read %x %.2x\n", which, offset, value);
	return value;
}

void lynx_state::lynx_timer_write(int which, int offset, uint8_t data)
{
	//logerror("timer %d write %x %.2x\n", which, offset, data);
	attotime t;

	if ( m_timer[which].timer_active && ((m_timer[which].cntrl1 & 0x07) != 0x07))
	{
		m_timer[which].counter = (uint8_t) (m_timer[which].timer->remaining().as_ticks(1000000>>(m_timer[which].cntrl1 & 0x07)));
		m_timer[which].counter -= (m_timer[which].counter) ? 1 : 0;
	}

	switch (offset)
	{
		case 0:
			m_timer[which].bakup = data;
			break;
		case 1:
			m_timer[which].cntrl1 = data;
			if (data & 0x40) // reset timer done
				m_timer[which].cntrl2 &= ~0x08;
			break;
		case 2:
			m_timer[which].counter = data;
			break;
		case 3:
			m_timer[which].cntrl2 = (m_timer[which].cntrl2 & ~0x08) | (data & 0x08);
			break;
	}

	/* Update timers */
	//if ( offset < 3 )
	//{
		m_timer[which].timer->reset();
		m_timer[which].timer_active = 0;
		if ((m_timer[which].cntrl1 & 0x08) && !(m_timer[which].cntrl2 & 0x08))      // if enable count
		{
			if ((m_timer[which].cntrl1 & 0x07) != 0x07)  // if not set to link mode
			{
				t = (attotime::from_hz(lynx_time_factor(m_timer[which].cntrl1 & 0x07)) * (m_timer[which].counter + 1));
				m_timer[which].timer->adjust(t, which);
				m_timer[which].timer_active = 1;
			}
		}
	//}
}


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

    UART Emulation

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


void lynx_state::lynx_uart_reset()
{
	memset(&m_uart, 0, sizeof(m_uart));
}

TIMER_CALLBACK_MEMBER(lynx_state::lynx_uart_loopback_timer)
{
	m_uart.received = false;
}

TIMER_CALLBACK_MEMBER(lynx_state::lynx_uart_timer)
{
	if (m_uart.buffer_loaded)
	{
		m_uart.data_to_send = m_uart.buffer;
		m_uart.buffer_loaded = false;
		timer_set(attotime::from_usec(11*16), TIMER_UART);
	}
	else
	{
		m_uart.sending = false;
		m_uart.received = true;
		m_uart.data_received = m_uart.data_to_send;
		timer_set(attotime::from_usec(11*16), TIMER_UART_LOOPBACK);
		if (m_uart.serctl & 0x40)
		{
			m_mikey.data[0x81] |= 0x10;
			m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
			m_maincpu->set_input_line(M65SC02_IRQ_LINE, ASSERT_LINE);
		}
	}

	if (m_uart.serctl & 0x80)
	{
		m_mikey.data[0x81] |= 0x10;
		m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
		m_maincpu->set_input_line(M65SC02_IRQ_LINE, ASSERT_LINE);
	}
}

READ8_MEMBER(lynx_state::lynx_uart_r)
{
	uint8_t value = 0x00;
	switch (offset)
	{
		case 0x8c:
			if (!m_uart.buffer_loaded)
				value |= 0x80;
			if (m_uart.received)
				value |= 0x40;
			if (!m_uart.sending)
				value |= 0x20;
			break;

		case 0x8d:
			value = m_uart.data_received;
			break;
	}
	logerror("uart read %.2x %.2x\n", offset, value);
	return value;
}

WRITE8_MEMBER(lynx_state::lynx_uart_w)
{
	logerror("uart write %.2x %.2x\n", offset, data);
	switch (offset)
	{
		case 0x8c:
			m_uart.serctl = data;
			break;

		case 0x8d:
			if (m_uart.sending)
			{
				m_uart.buffer = data;
				m_uart.buffer_loaded = true;
			}
			else
			{
				m_uart.sending = true;
				m_uart.data_to_send = data;
				// timing not accurate, baude rate should be calculated from timer 4 backup value and clock rate
				timer_set(attotime::from_usec(11*16), TIMER_UART);
			}
			break;
	}
}


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

    Mikey memory handlers

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


READ8_MEMBER(lynx_state::mikey_read)
{
	uint8_t direction, value = 0x00;

	switch (offset)
	{
	case 0x00: case 0x01: case 0x02: case 0x03:
	case 0x04: case 0x05: case 0x06: case 0x07:
	case 0x08: case 0x09: case 0x0a: case 0x0b:
	case 0x0c: case 0x0d: case 0x0e: case 0x0f:
	case 0x10: case 0x11: case 0x12: case 0x13:
	case 0x14: case 0x15: case 0x16: case 0x17:
	case 0x18: case 0x19: case 0x1a: case 0x1b:
	case 0x1c: case 0x1d: case 0x1e: case 0x1f:
		value = lynx_timer_read(offset >> 2, offset & 0x03);
		break;

	case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: case 0x25: case 0x26: case 0x27:
	case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
	case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
	case 0x38: case 0x39: case 0x3a: case 0x3b: case 0x3c: case 0x3d: case 0x3e: case 0x3f:
	case 0x40: case 0x41: case 0x42: case 0x43: case 0x44: case 0x50:
		value = m_sound->read(space, offset);
		break;

	case 0x80:
	case 0x81:
		value = m_mikey.data[0x81]; // both registers access the same interrupt status byte
		// logerror( "mikey read %.2x %.2x\n", offset, value );
		break;

	case 0x84:
	case 0x85:
		value = 0x00;
		break;

	case 0x86:
		value = 0x80;
		break;

	case 0x88:
		value = 0x01;
		break;

	case 0x8b:
		direction = m_mikey.data[0x8a];
		value |= (direction & 0x01) ? (m_mikey.data[offset] & 0x01) : 0x01; // External Power input
		value |= (direction & 0x02) ? (m_mikey.data[offset] & 0x02) : 0x00; // Cart Address Data output (0 turns cart power on)
		value |= (direction & 0x04) ? (m_mikey.data[offset] & 0x04) : 0x04; // noexp input
		// REST read returns actual rest state anded with rest output bit
		value |= (direction & 0x08) ? (((m_mikey.data[offset] & 0x08) && (m_mikey.vb_rest)) ? 0x00 : 0x08) : 0x00;  // rest output
		value |= (direction & 0x10) ? (m_mikey.data[offset] & 0x10) : 0x10; // audin input
		/* Hack: we disable COMLynx  */
		value |= 0x04;
		/* B5, B6 & B7 are not used */
		break;

	case 0x8c:
	case 0x8d:
		value = lynx_uart_r(space, offset, mem_mask);
		break;

	default:
		value = m_mikey.data[offset];
		//logerror( "mikey read %.2x %.2x\n", offset, value );
	}
	return value;
}

WRITE8_MEMBER(lynx_state::mikey_write)
{
	switch (offset)
	{
	case 0x00: case 0x01: case 0x02: case 0x03:
	case 0x04: case 0x05: case 0x06: case 0x07:
	case 0x08: case 0x09: case 0x0a: case 0x0b:
	case 0x0c: case 0x0d: case 0x0e: case 0x0f:
	case 0x10: case 0x11: case 0x12: case 0x13:
	case 0x14: case 0x15: case 0x16: case 0x17:
	case 0x18: case 0x19: case 0x1a: case 0x1b:
	case 0x1c: case 0x1d: case 0x1e: case 0x1f:
		lynx_timer_write(offset >> 2, offset & 3, data);
		return;

	case 0x20: case 0x21: case 0x22: case 0x23: case 0x24: case 0x25: case 0x26: case 0x27:
	case 0x28: case 0x29: case 0x2a: case 0x2b: case 0x2c: case 0x2d: case 0x2e: case 0x2f:
	case 0x30: case 0x31: case 0x32: case 0x33: case 0x34: case 0x35: case 0x36: case 0x37:
	case 0x38: case 0x39: case 0x3a: case 0x3b: case 0x3c: case 0x3d: case 0x3e: case 0x3f:
	case 0x40: case 0x41: case 0x42: case 0x43: case 0x44: case 0x50:
		m_sound->write(space, offset, data);
		return;

	case 0x80:
		m_mikey.data[0x81] &= ~data; // clear interrupt source
		// logerror("mikey write %.2x %.2x\n", offset, data);
		if (!m_mikey.data[0x81])
			m_maincpu->set_input_line(M65SC02_IRQ_LINE, CLEAR_LINE);
		break;

	/* Is this correct? */ // Notes say writing to register will result in interrupt being triggered.
	case 0x81:
		m_mikey.data[0x81] |= data;
		if (data)
		{
			m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
			m_maincpu->set_input_line(M65SC02_IRQ_LINE, ASSERT_LINE);
			logerror("direct write to interrupt register\n");
		}
		break;

	case 0x87:
		m_mikey.data[offset] = data;
		if (data & 0x02)        // Power (1 = on)
		{
			if (data & 0x01)    // Cart Address Strobe
			{
				m_suzy.high <<= 1;
				if (m_mikey.data[0x8b] & 0x02)
					m_suzy.high |= 1;
				m_suzy.high &= 0xff;
				m_suzy.low = 0;
			}
		}
		else
		{
			m_suzy.high = 0;
			m_suzy.low = 0;
		}
		break;

	case 0x8c: case 0x8d:
		lynx_uart_w(space, offset, data);
		break;

	case 0xa0: case 0xa1: case 0xa2: case 0xa3: case 0xa4: case 0xa5: case 0xa6: case 0xa7:
	case 0xa8: case 0xa9: case 0xaa: case 0xab: case 0xac: case 0xad: case 0xae: case 0xaf:
	case 0xb0: case 0xb1: case 0xb2: case 0xb3: case 0xb4: case 0xb5: case 0xb6: case 0xb7:
	case 0xb8: case 0xb9: case 0xba: case 0xbb: case 0xbc: case 0xbd: case 0xbe: case 0xbf:
		m_mikey.data[offset] = data;

		/* RED = 0xb- & 0x0f, GREEN = 0xa- & 0x0f, BLUE = (0xb- & 0xf0) >> 4 */
		m_lynx_palette[offset & 0x0f] = m_palette->pen(
			((m_mikey.data[0xb0 + (offset & 0x0f)] & 0x0f)) |
			((m_mikey.data[0xa0 + (offset & 0x0f)] & 0x0f) << 4) |
			((m_mikey.data[0xb0 + (offset & 0x0f)] & 0xf0) << 4));
		break;

	/* TODO: properly implement these writes */
	case 0x8b:
		m_mikey.data[offset] = data;
		if (m_mikey.data[0x8a] & 0x10)
			logerror("Trying to enable bank 1 write. %d\n", m_mikey.data[offset] & 0x10);
		break;

	//case 0x90: // SDONEACK - Suzy Done Acknowledge
	case 0x91: // CPUSLEEP - CPU Bus Request Disable
		m_mikey.data[offset] = data;
		if (!data && m_blitter.busy)
		{
			m_maincpu->set_input_line(INPUT_LINE_HALT, ASSERT_LINE);
			/* A write of '0' to this address will reset the CPU bus request flip flop */
		}
		break;
	case 0x94: case 0x95:
		m_mikey.data[offset]=data;
		break;
	case 0x9c: case 0x9d: case 0x9e:
		m_mikey.data[offset]=data;
		logerror("Mtest%d write: %x\n", offset&0x3, data);
		break;

	default:
		m_mikey.data[offset]=data;
		//logerror("mikey write %.2x %.2x\n",offset,data);
		break;
	}
}

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

    Init / Config

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

READ8_MEMBER(lynx_state::lynx_memory_config_r)
{
	return m_memory_config;
}

WRITE8_MEMBER(lynx_state::lynx_memory_config_w)
{
	/* bit 7: hispeed, uses page mode accesses (4 instead of 5 cycles )
	 * when these are safe in the cpu */
	m_memory_config = data;

	if (data & 1)
	{
		space.install_readwrite_bank(0xfc00, 0xfcff, "bank1");
		membank("bank1")->set_base(m_mem_fc00);
	}
	else
		space.install_readwrite_handler(0xfc00, 0xfcff, read8_delegate(FUNC(lynx_state::suzy_read),this), write8_delegate(FUNC(lynx_state::suzy_write),this));

	if (data & 2)
	{
		space.install_readwrite_bank(0xfd00, 0xfdff, "bank2");
		membank("bank2")->set_base(m_mem_fd00);
	}
	else
		space.install_readwrite_handler(0xfd00, 0xfdff, read8_delegate(FUNC(lynx_state::mikey_read),this), write8_delegate(FUNC(lynx_state::mikey_write),this));

	membank("bank3")->set_entry((data & 4) ? 1 : 0);
	membank("bank4")->set_entry((data & 8) ? 1 : 0);
}

void lynx_state::machine_reset()
{
	lynx_memory_config_w(m_maincpu->space(AS_PROGRAM), 0, 0);

	m_maincpu->set_input_line(INPUT_LINE_HALT, CLEAR_LINE);
	m_maincpu->set_input_line(M65SC02_IRQ_LINE, CLEAR_LINE);

	memset(&m_suzy, 0, sizeof(m_suzy));
	memset(&m_mikey, 0, sizeof(m_mikey));

	m_suzy.data[0x88]  = 0x01;
	m_suzy.data[0x90]  = 0x00;
	m_suzy.data[0x91]  = 0x00;
	m_mikey.data[0x80] = 0x00;
	m_mikey.data[0x81] = 0x00;
	m_mikey.data[0x88] = 0x01;
	m_mikey.data[0x8a] = 0x00;
	m_mikey.data[0x8c] = 0x00;
	m_mikey.data[0x90] = 0x00;
	m_mikey.data[0x92] = 0x00;

	lynx_uart_reset();

	// hack to allow current object loading to work
#if 0
	lynx_timer_write( this, 0, 0, 160 ); // set backup value (hpos) = 160
	lynx_timer_write( this, 0, 1, 0x10 | 0x8 | 0 ); // enable count, enable reload, 1us period
	lynx_timer_write( this, 2, 0, 105 ); // set backup value (vpos) = 102
	lynx_timer_write( this, 2, 1, 0x10 | 0x8 | 7 ); // enable count, enable reload, link
#endif

	render_target *target = machine().render().first_target();
	target->set_view(m_rotate);
}

void lynx_state::lynx_postload()
{
	lynx_memory_config_w(m_maincpu->space(AS_PROGRAM), 0, m_memory_config);
}

void lynx_state::machine_start()
{
	m_bitmap_temp.allocate(160,102,0,0);

	// save driver variables
	save_item(NAME(m_memory_config));
	save_item(NAME(m_sign_AB));
	save_item(NAME(m_sign_CD));
	save_item(NAME(m_lynx_palette));
	save_item(NAME(m_rotate));
	// save blitter variables
	save_item(NAME(m_blitter.screen));
	save_item(NAME(m_blitter.colbuf));
	save_item(NAME(m_blitter.colpos));
	save_item(NAME(m_blitter.xoff));
	save_item(NAME(m_blitter.yoff));
	save_item(NAME(m_blitter.mode));
	save_item(NAME(m_blitter.spr_coll));
	save_item(NAME(m_blitter.spritenr));
	save_item(NAME(m_blitter.x_pos));
	save_item(NAME(m_blitter.y_pos));
	save_item(NAME(m_blitter.width));
	save_item(NAME(m_blitter.height));
	save_item(NAME(m_blitter.tilt_accumulator));
	save_item(NAME(m_blitter.width_accumulator));
	save_item(NAME(m_blitter.height_accumulator));
	save_item(NAME(m_blitter.width_offset));
	save_item(NAME(m_blitter.height_offset));
	save_item(NAME(m_blitter.stretch));
	save_item(NAME(m_blitter.tilt));
	save_item(NAME(m_blitter.color));
	save_item(NAME(m_blitter.bitmap));
	save_item(NAME(m_blitter.use_rle));
	save_item(NAME(m_blitter.line_color));
	save_item(NAME(m_blitter.spr_ctl0));
	save_item(NAME(m_blitter.spr_ctl1));
	save_item(NAME(m_blitter.scb));
	save_item(NAME(m_blitter.scb_next));
	save_item(NAME(m_blitter.sprite_collide));
	save_item(NAME(m_blitter.everon));
	save_item(NAME(m_blitter.fred));
	save_item(NAME(m_blitter.memory_accesses));
	save_item(NAME(m_blitter.no_collide));
	save_item(NAME(m_blitter.vstretch));
	save_item(NAME(m_blitter.lefthanded));
	save_item(NAME(m_blitter.busy));
	// save suzy variables
	save_item(NAME(m_suzy.data));
	save_item(NAME(m_suzy.high));
	save_item(NAME(m_suzy.low));
	save_item(NAME(m_suzy.signed_math));
	save_item(NAME(m_suzy.accumulate));
	save_item(NAME(m_suzy.accumulate_overflow));
	// save mikey variables
	save_item(NAME(m_mikey.data));
	save_item(NAME(m_mikey.disp_addr));
	save_item(NAME(m_mikey.vb_rest));
	// save uart variables
	save_item(NAME(m_uart.serctl));
	save_item(NAME(m_uart.data_received));
	save_item(NAME(m_uart.data_to_send));
	save_item(NAME(m_uart.buffer));
	save_item(NAME(m_uart.received));
	save_item(NAME(m_uart.sending));
	save_item(NAME(m_uart.buffer_loaded));

	machine().save().register_postload(save_prepost_delegate(FUNC(lynx_state::lynx_postload), this));

	membank("bank3")->configure_entry(0, memregion("maincpu")->base() + 0x0000);
	membank("bank3")->configure_entry(1, m_mem_fe00);
	membank("bank4")->configure_entry(0, memregion("maincpu")->base() + 0x01fa);
	membank("bank4")->configure_entry(1, m_mem_fffa);

	for (int i = 0; i < NR_LYNX_TIMERS; i++)
		lynx_timer_init(i);
}


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

    Image handling

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

image_verify_result lynx_state::lynx_verify_cart(char *header, int kind)
{
	if (kind)
	{
		if (strncmp("BS93", &header[6], 4))
		{
			logerror("This is not a valid Lynx image\n");
			return image_verify_result::FAIL;
		}
	}
	else
	{
		if (strncmp("LYNX", &header[0], 4))
		{
			if (!strncmp("BS93", &header[6], 4))
			{
				logerror("This image is probably a Quickload image with .lnx extension\n");
				logerror("Try to load it with -quickload\n");
			}
			else
				logerror("This is not a valid Lynx image\n");
			return image_verify_result::FAIL;
		}
	}

	return image_verify_result::PASS;
}

DEVICE_IMAGE_LOAD_MEMBER( lynx_state, lynx_cart )
{
	/* Lynx carts have 19 address lines, the upper 8 used for bank select. The lower
	11 bits are used to address data within the selected bank. Valid bank sizes are 256,
	512, 1024 or 2048 bytes. Commercial roms use all 256 banks.*/
	uint32_t size = m_cart->common_get_size("rom");
	uint16_t gran = 0;

	if (!image.loaded_through_softlist())
	{
		// check for lnx header
		if (image.is_filetype("lnx"))
		{
			// 64 byte header
			// LYNX
			// intelword lower counter size
			// 0 0 1 0
			// 32 chars name
			// 22 chars manufacturer
			uint8_t header[0x40];
			image.fread(header, 0x40);

			// Check the image
			if (lynx_verify_cart((char*)header, LYNX_CART) != image_verify_result::PASS)
				return image_init_result::FAIL;

			/* 2008-10 FP: According to Handy source these should be page_size_bank0. Are we using
			 it correctly in MESS? Moreover, the next two values should be page_size_bank1. We should
			 implement this as well */
			gran = header[4] | (header[5] << 8);

			logerror ("%s %dkb cartridge with %dbyte granularity from %s\n", header + 10, size / 1024, gran, header + 42);
			size -= 0x40;
		}
	}

	m_cart->rom_alloc(size, GENERIC_ROM8_WIDTH, ENDIANNESS_LITTLE);
	m_cart->common_load_rom(m_cart->get_rom_base(), size, "rom");

	// set-up granularity
	if (!image.loaded_through_softlist())
	{
		if (image.is_filetype("lnx"))     // from header
			m_granularity = gran;
		else if (image.is_filetype("lyx"))
		{
			/* 2008-10 FP: FIXME: .lyx file don't have an header, hence they miss "lynx_granularity"
			(see above). What if bank 0 has to be loaded elsewhere? And what about bank 1?
			These should work with most .lyx files, but we need additional info on raw cart images */
			if (size == 0x20000)
				m_granularity = 0x0200;
			else if (size == 0x80000)
				m_granularity = 0x0800;
			else
				m_granularity = 0x0400;
		}
	}
	else
	{
		if (size > 0xffff) // 64,128,256,512k cartridges
			m_granularity = size >> 8;
		else
			m_granularity = 0x400; // Homebrew roms not using all 256 banks (T-Tris) (none currently in softlist)
	}

	// set-up rotation from softlist
	if (image.loaded_through_softlist())
	{
		const char *rotate = image.get_feature("rotation");
		m_rotate = 0;
		if (rotate)
		{
			if (!core_stricmp(rotate, "RIGHT"))
				m_rotate = 1;
			else if (!core_stricmp(rotate, "LEFT"))
				m_rotate = 2;
		}

	}

	return image_init_result::PASS;
}