175:, with every data line paired with a dedicated return line. It is the voltage difference between these two lines that defines the mark and space, rather than, as in RS-232, the difference in voltage between a data line and a local ground. As the ground voltage can differ at either end of the cable, this required RS-232 to use signals with voltage magnitudes greater than 5 volts. Moving to dedicated return lines and always defining ground in reference to the sender allows RS-422 to use 0.4 V, allowing it to run at much higher speeds. RS-423 differs primarily in that it has a single return pin instead of one for each data pin.
231:
1363:
138:
247:
termination, as well as the individual installation. Figure A.1 shows a maximum length of 1,200 meters (3,900 ft), but this is with a termination, and the annex discusses the fact that many applications can tolerate greater timing and amplitude distortion, and that experience has shown that the cable length may be extended to several kilometers. Conservative maximum data rates with 24
314:, often with each pair being shielded, and a ground wire. While a double-pair cable may be practical for many RS-422 applications, the RS-422 specification only defines one signal path and does not assign any function to it. Any complete cable assembly with connectors should be labeled with the specification that defined the signal function and mechanical layout of the connector, such as
261:
RS-422 specifies the electrical characteristics of a single balanced signal. The standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications which require a balanced voltage circuit to transmit data. These other standards would define
246:
The maximum cable length is not specified in the standard, but guidance is given in its annex. (This annex is not a formal part of the standard, but is included for information purposes only.) Limitations on line length and data rate vary with the parameters of the cable length, balance, and
238:
Several key advantages offered by this standard include the differential receiver, a differential driver and data rates as high as 10 megabits per second at 12 meters (40 ft). Since the signal quality degrades with cable length, the maximum data rate decreases as cable length
258:) cable are 10 Mbit/s at 12 m (39 ft) to 90 kbit/s at 1,200 m (3,900 ft), as shown in the figure A.1. This figure is a conservative guide based on empirical data, not a limit imposed by the standard.
342:-8 connector. The ports could be put into either RS-232 or RS-422 mode, which changes the behavior of some of the pins while turning others on or off completely. These connectors are used to support RS-232 devices like
296:
signal, while MIL-STD-188-114B uses a signal symmetric about 0 V. However, the tolerance for common-mode voltage in both specifications allows them to interoperate. Care must be taken with the termination network.
156:, first issued in 1975, that specifies electrical characteristics of a digital signaling circuit. It was meant to be the foundation of a suite of standards that would replace the older
281:
RS-422 cannot implement a true multi-point communications network, such as with EIA-485, since there can be only one driver on each pair of wires. However, one driver can
160:
standard with standards that offered much higher speed, better immunity from noise, and longer cable lengths. RS-422 systems can transmit data at rates as high as 10
350:
networking, RS-422 printers, and other peripherals. Two such ports were part of early Apple
Macintosh series designs until they were replaced, along with
278:
connector) use RS-422 electrical signals. Some RS-422 devices have 4 screw terminals for pairs of wire, with one pair used for data in each direction.
218:
The first version of RS-422 was issued in 1975, with revision A issued in
December 1978. Revision B, published in May 1994 was reaffirmed by the
467:"V.11 : Electrical characteristics for balanced double-current interchange circuits operating at data signalling rates up to 10 Mbit/s"
1358:
Interfaces are listed by their speed in the (roughly) ascending order, so the interface at the end of each section should be the fastest.
803:
203:
specify the electrical characteristics of the balanced voltage digital interface circuit. RS-422 provides for data transmission, using
1331:
547:
1395:
960:
365:
RS-422 is a common transport mechanism for RS-232 extenders. These consist of RS-232 ports on either end of an RS-422 connection.
823:
219:
630:
471:
184:
1011:
682:
717:
1064:
903:
833:
893:
53:
330:
computers. This was implemented in a multi-pin connector that had enough pins to support the majority of the common
991:
783:
513:
409:
153:
1335:
986:
955:
608:
164:, or may be sent on cables as long as 1,200 meters (3,900 ft) at lower rates. It is closely related to
933:
493:
TIA/EIA STANDARD, Electrical
Characteristics of Balanced Voltage Digital Interface Circuits, TIA/EIA-422-B
1259:
1198:
1053:
255:
858:
623:
1228:
565:"Maxim IC Application Note 723 'Selecting and Using RS-232, RS-422, and RS-485 Serial Data Standards'"
913:
526:
251:
1366:
1341:
1233:
888:
580:"Texas Instruments Application Report '422 and 485 Standards Overview and System Configurations'"
189:
ANSI/TIA/EIA-422-B Electrical
Characteristics of Balanced Voltage Differential Interface Circuits
310:
When used in relation to communications wiring, RS-422 wiring refers to cable made of 2 sets of
1385:
923:
380:
208:
204:
172:
1390:
1187:
1140:
996:
768:
616:
419:
1183:
1036:
918:
395:
industry standard connector for RS-422, which is still found on broadcast equipment today.
369:
355:
8:
1095:
650:
639:
564:
1085:
707:
643:
509:
351:
211:
or non-terminated transmission lines, point to point, or multi-drop. In contrast to
818:
594:
579:
404:
948:
798:
778:
653:
379:
facilities used RS-422A to remotely control the players/recorders located in the
373:
200:
1249:
943:
868:
793:
697:
672:
384:
376:
168:, which uses the same signaling systems but on a different wiring arrangement.
230:
1379:
1321:
1208:
1100:
1048:
1031:
813:
712:
702:
677:
638:
57:
1058:
1001:
853:
758:
311:
215:, RS-422/V.11 does not allow multiple drivers but only multiple receivers.
1326:
1305:
1223:
1068:
1006:
981:
908:
692:
687:
595:"Texas Instruments Application Report SLLA067B 'Comparing Bus Solutions'"
335:
289:
1145:
466:
262:
protocols, connectors, pin assignments and functions. Standards such as
1179:
878:
667:
239:
increases. Figure A.1 in the annex plotting this stops at 10
1203:
1193:
1160:
1155:
1090:
965:
753:
738:
733:
347:
327:
1213:
1150:
883:
743:
424:
414:
392:
339:
1346:
1300:
1284:
1110:
928:
873:
808:
763:
300:
282:
271:
263:
240:
212:
161:
157:
137:
1279:
1170:
1135:
1130:
1120:
938:
828:
788:
748:
331:
315:
304:
165:
1264:
1175:
368:
Before hard-disk-based playout and editing systems were used,
1274:
1165:
1105:
1043:
1016:
898:
848:
773:
343:
275:
267:
1269:
1254:
1115:
1026:
1021:
863:
444:
388:
359:
326:
One of the most widespread uses of RS-422 was on the early
293:
292:, but they are not identical. RS-422 uses a nominal 0 to 5-
1218:
843:
838:
248:
234:
Data rate versus line length chart, from RS-422 Annex A.1
303:
is a similar specification for unbalanced signaling (
288:
RS-422 can interoperate with interfaces designed to
1377:
961:Coherent Accelerator Processor Interface (CAPI)
99:−6 to +6 V (maximum voltage for each line)
624:
506:Microcomputers and Modern Control Engineering
152:, is a technical standard originated by the
574:. Maxim Integrated Products. December 2000.
631:
617:
387:connection was used, which makes use of a
486:
183:RS-422 is the common short form title of
229:
136:
220:Telecommunications Industry Association
1378:
207:, with unidirectional/non-reversible,
141:RS-422 network with multiple receivers
612:
472:International Telecommunication Union
338:, but this was quickly replaced by a
185:American National Standards Institute
334:pins; the first models used a 9-pin
205:balanced, or differential, signaling
13:
604:. Texas Instruments. October 2009.
557:
508:, Reston Publishing Company, 1983
225:
14:
1407:
191:and its international equivalent
178:
16:Standard for serial communication
1362:
1361:
123:Tx+, Tx−, Rx+, Rx− (full duplex)
1396:Serial communication interfaces
589:. Texas Instruments. June 2002.
527:"First Macintosh Press Release"
321:
193:ITU-T Recommendation T-REC-V.11
541:
519:
498:
459:
437:
410:Electronic Industries Alliance
154:Electronic Industries Alliance
67:10 (1 driver and 10 receivers)
1:
956:Intel Ultra Path Interconnect
430:
934:Intel QuickPath Interconnect
924:Direct Media Interface (DMI)
75:1,200 meters (3,900 ft)
7:
398:
91:100 kbit/s – 10 Mbit/s
10:
1412:
919:Compute Express Link (CXL)
548:Sony 9-Pin Remote Protocol
1355:
1314:
1293:
1242:
1156:IEEE-1284 (parallel port)
1078:
1071:logical device interface)
974:
726:
660:
127:
119:
111:
103:
95:
87:
79:
71:
63:
49:
41:
36:
28:
23:
285:to up to ten receivers.
391:connector. This is the
718:List of bus bandwidths
381:central apparatus room
235:
173:differential signaling
142:
420:List of network buses
233:
140:
1161:IEEE-1394 (FireWire)
899:PCI Extended (PCI-X)
529:. stanford.edu. 1984
504:Douglas A. Cassell,
383:. In most cases the
370:broadcast automation
356:Universal Serial Bus
37:Protocol information
1002:Parallel ATA (PATA)
572:MaximIntegrated.com
115:Positive difference
107:Negative difference
88:Maximum binary rate
909:PCI Express (PCIe)
236:
199:. These technical
143:
1373:
1372:
1359:
1086:Apple Desktop Bus
1063:PCI Express (via
1022:Serial ATA (SATA)
708:Network on a chip
171:RS-422 specifies
135:
134:
120:Available signals
80:Mode of operation
56:, unidirectional
1403:
1365:
1364:
1357:
819:HP Precision Bus
633:
626:
619:
610:
609:
605:
599:
590:
584:
575:
569:
551:
545:
539:
538:
536:
534:
523:
517:
502:
496:
490:
484:
483:
481:
479:
463:
457:
456:
454:
452:
441:
405:Differential TTL
290:MIL-STD-188-114B
195:, also known as
187:(ANSI) standard
148:, also known as
72:Maximum distance
50:Network topology
21:
20:
1411:
1410:
1406:
1405:
1404:
1402:
1401:
1400:
1376:
1375:
1374:
1369:
1360:
1351:
1310:
1289:
1238:
1151:IEEE-488 (GPIB)
1074:
970:
949:Infinity Fabric
779:Europe Card Bus
722:
656:
637:
597:
593:
582:
578:
567:
563:
560:
558:Further reading
555:
554:
546:
542:
532:
530:
525:
524:
520:
503:
499:
491:
487:
477:
475:
465:
464:
460:
450:
448:
443:
442:
438:
433:
401:
374:post-production
324:
270:connector) and
228:
226:Characteristics
181:
128:Connector types
64:Maximum devices
17:
12:
11:
5:
1409:
1399:
1398:
1393:
1388:
1371:
1370:
1356:
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1324:
1318:
1316:
1312:
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1309:
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1303:
1297:
1295:
1291:
1290:
1288:
1287:
1282:
1277:
1272:
1267:
1262:
1260:Intel HD Audio
1257:
1252:
1250:ADAT Lightpipe
1246:
1244:
1240:
1239:
1237:
1236:
1231:
1226:
1221:
1216:
1211:
1206:
1201:
1196:
1191:
1173:
1168:
1163:
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1148:
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1138:
1133:
1128:
1123:
1118:
1113:
1108:
1103:
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1088:
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1080:
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1075:
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1034:
1024:
1019:
1014:
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1004:
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994:
989:
984:
978:
976:
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971:
969:
968:
963:
958:
953:
952:
951:
944:HyperTransport
941:
936:
931:
926:
921:
916:
911:
906:
901:
896:
891:
886:
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876:
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846:
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836:
831:
826:
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786:
781:
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771:
766:
761:
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751:
746:
741:
736:
730:
728:
724:
723:
721:
720:
715:
710:
705:
700:
698:Bus contention
695:
690:
685:
680:
675:
673:Front-side bus
670:
664:
662:
658:
657:
654:computer buses
636:
635:
628:
621:
613:
607:
606:
591:
576:
559:
556:
553:
552:
540:
518:
497:
485:
458:
435:
434:
432:
429:
428:
427:
422:
417:
412:
407:
400:
397:
377:linear editing
323:
320:
227:
224:
180:
179:Standard scope
177:
133:
132:
129:
125:
124:
121:
117:
116:
113:
109:
108:
105:
101:
100:
97:
93:
92:
89:
85:
84:
81:
77:
76:
73:
69:
68:
65:
61:
60:
54:Point-to-point
51:
47:
46:
43:
42:Physical media
39:
38:
34:
33:
30:
26:
25:
15:
9:
6:
4:
3:
2:
1408:
1397:
1394:
1392:
1389:
1387:
1386:EIA standards
1384:
1383:
1381:
1368:
1354:
1348:
1345:
1343:
1340:
1337:
1333:
1330:
1328:
1325:
1323:
1322:Multidrop bus
1320:
1319:
1317:
1313:
1307:
1304:
1302:
1299:
1298:
1296:
1292:
1286:
1283:
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1268:
1266:
1263:
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1258:
1256:
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1247:
1245:
1241:
1235:
1232:
1230:
1229:External PCIe
1227:
1225:
1222:
1220:
1217:
1215:
1212:
1210:
1209:Parallel SCSI
1207:
1205:
1202:
1200:
1197:
1195:
1192:
1189:
1185:
1181:
1177:
1174:
1172:
1169:
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1159:
1157:
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1142:
1139:
1137:
1134:
1132:
1129:
1127:
1124:
1122:
1119:
1117:
1114:
1112:
1109:
1107:
1104:
1102:
1101:Commodore bus
1099:
1097:
1094:
1092:
1089:
1087:
1084:
1083:
1081:
1077:
1070:
1066:
1062:
1060:
1057:
1055:
1052:
1050:
1049:Fibre Channel
1047:
1045:
1042:
1038:
1035:
1033:
1030:
1029:
1028:
1025:
1023:
1020:
1018:
1015:
1013:
1010:
1008:
1005:
1003:
1000:
998:
995:
993:
990:
988:
985:
983:
980:
979:
977:
973:
967:
964:
962:
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954:
950:
947:
946:
945:
942:
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937:
935:
932:
930:
927:
925:
922:
920:
917:
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910:
907:
905:
902:
900:
897:
895:
892:
890:
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882:
880:
877:
875:
872:
870:
867:
865:
862:
860:
857:
855:
852:
850:
847:
845:
842:
840:
837:
835:
832:
830:
827:
825:
822:
820:
817:
815:
812:
810:
807:
805:
802:
800:
797:
795:
792:
790:
787:
785:
782:
780:
777:
775:
772:
770:
767:
765:
762:
760:
757:
755:
752:
750:
747:
745:
742:
740:
737:
735:
732:
731:
729:
725:
719:
716:
714:
713:Plug and play
711:
709:
706:
704:
703:Bus mastering
701:
699:
696:
694:
691:
689:
686:
684:
681:
679:
678:Back-side bus
676:
674:
671:
669:
666:
665:
663:
659:
655:
652:
648:
646:
641:
634:
629:
627:
622:
620:
615:
614:
611:
603:
596:
592:
588:
581:
577:
573:
566:
562:
561:
549:
544:
528:
522:
515:
511:
507:
501:
494:
489:
474:
473:
468:
462:
446:
440:
436:
426:
423:
421:
418:
416:
413:
411:
408:
406:
403:
402:
396:
394:
390:
386:
382:
378:
375:
371:
366:
363:
361:
357:
353:
349:
345:
341:
337:
333:
329:
319:
317:
313:
308:
306:
302:
298:
295:
291:
286:
284:
279:
277:
273:
269:
265:
259:
257:
253:
250:
244:
242:
232:
223:
221:
216:
214:
210:
206:
202:
198:
194:
190:
186:
176:
174:
169:
167:
163:
159:
155:
151:
147:
139:
131:Not specified
130:
126:
122:
118:
114:
110:
106:
102:
98:
94:
90:
86:
82:
78:
74:
70:
66:
62:
59:
58:multidrop bus
55:
52:
48:
44:
40:
35:
31:
27:
22:
19:
1391:Serial buses
1125:
854:TURBOchannel
644:
602:Focus.TI.com
601:
587:Focus.TI.com
586:
571:
543:
531:. Retrieved
521:
505:
500:
492:
488:
478:19 September
476:. Retrieved
470:
461:
449:. Retrieved
447:. foldoc.org
439:
372:systems and
367:
364:
325:
322:Applications
312:twisted pair
309:
299:
287:
280:
260:
245:
237:
217:
196:
192:
188:
182:
170:
149:
145:
144:
83:Differential
45:Twisted pair
18:
1327:CoreConnect
1306:ExpressCard
1234:Thunderbolt
1224:Camera Link
1007:Bus and Tag
693:Address bus
688:Control bus
683:Daisy chain
336:D connector
150:TIA/EIA-422
32:TIA/EIA-422
1380:Categories
1180:ACCESS.bus
1079:Peripheral
879:InfiniBand
874:HP GSC bus
668:System bus
514:0835943658
495:, May 1994
431:References
385:Sony 9-pin
354:ports, by
209:terminated
1141:Lightning
1091:Atari SIO
966:SpaceWire
799:Zorro III
739:S-100 bus
734:SS-50 bus
727:Standards
647:standards
640:Technical
445:"EIA-423"
362:in 1998.
348:AppleTalk
328:Macintosh
222:in 2005.
201:standards
1367:Category
1342:Wishbone
1315:Embedded
1294:Portable
1214:Profibus
1146:DMX512-A
1032:Parallel
884:Ethernet
794:Zorro II
744:Multibus
645:de facto
516:page 569
425:Profibus
415:Fieldbus
399:See also
393:de facto
340:mini-DIN
112:Space(0)
29:Standard
1347:SLIMbus
1301:PC Card
1285:TOSLINK
975:Storage
929:RapidIO
809:FASTBUS
764:STD Bus
661:General
358:on the
301:EIA-423
283:fan-out
272:EIA-449
264:EIA-530
213:EIA-485
158:RS-232C
104:Mark(1)
96:Voltage
1280:S/PDIF
1171:1-Wire
1136:RS-485
1131:RS-423
1126:RS-422
1121:RS-232
982:ST-506
939:NVLink
789:STEbus
749:Unibus
533:8 July
512:
451:8 July
344:modems
332:RS-232
316:RS-449
305:RS-423
241:Mbit/s
166:RS-423
162:Mbit/s
146:RS-422
24:RS-422
1275:McASP
1243:Audio
1188:SMBus
1184:PMBus
1166:UNI/O
1106:HP-IL
1059:SATAe
1044:ESCON
1017:HIPPI
849:NuBus
804:CAMAC
774:Q-Bus
769:SMBus
754:VAXBI
651:wired
598:(PDF)
583:(PDF)
568:(PDF)
276:DC-37
268:DB-25
1332:AMBA
1270:MADI
1255:AES3
1116:MIDI
1069:NVMe
1065:AHCI
1027:SCSI
1012:DSSI
987:ESDI
864:SBus
824:EISA
759:MBus
649:for
642:and
535:2021
510:ISBN
480:2022
453:2021
389:DE-9
360:iMac
294:volt
256:POTS
197:X.27
1336:AXI
1265:I²S
1219:USB
1204:D²B
1199:SPI
1194:I3C
1176:I²C
1111:HIL
1096:DCB
1067:or
1054:SSA
1037:SAS
997:SMD
992:IPI
914:AGP
904:PXI
894:PCI
889:UPA
869:VLB
859:MCA
844:VPX
839:VXS
834:VXI
829:VME
814:LPC
784:ISA
352:ADB
307:).
252:UTP
249:AWG
1382::
1186:,
1182:,
600:.
585:.
570:.
469:.
346:,
318:.
243:.
1338:)
1334:(
1190:)
1178:(
632:e
625:t
618:v
550:.
537:.
482:.
455:.
274:(
266:(
254:(
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