1、L- EIA 493 82 = 323VbOO 0073306 5 EIA STANDARD I INTERFACE BETWEEN A NUMERICAL CONTROL UNIT AND PERIPHERAL EQUIPMENT _ EMPLOYING ASYNCHRONOUS BINARY DATA INTERCHANGE OVER CIRCUITS HAVING RS-423-A ELECTRICAL CHARACTERISTICS OCTOBER 1982 I Engineering Department . ELECTRONIC INDUSTRIES ASSOCIATION COP
2、YRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesEIA 493 82 m 3234600 0073307 7 m lt * NOTICE . EIA Engineering Standards and Publications are designed to serve the public interest through eljminating misunderstandings between manufacturers and purchasers, facilitating i
3、nterchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need Existence of such Standards and Pub- lications shall not in any respect preclude any member or non-member of EIA from manufacturing or s
4、elling products not conforming to such Standards and Publications, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than EIA members, whether the .standard is to be used either domestically or internationally. Recommended Standards and Publicatio
5、ns are adopted by EIA and NEMA without regard to whether or not their adoption may involye patents on articles, materials, or processes. By such action, EIA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Recommended Standard or P
6、ublication. This EIA Recommended Standard is considered to have international stan- dardization implications, but the IEC (or ISO) activity has not pwgressed to the point where a valid comparison between the EIA Recommended Standard and the IEC (or ISO) Recommendation can be made. Published by ELECT
7、RONIC INDUSTRIES ASSOCIATION Engineering, Department 2001 Eye Street, N.W. Washington, D.C. 20006 Copyright 1982 ELECTRONIC INDUSTRIES ASSOCIATION All rights reserved PRICE: $9.00 Printed -in U.S.A. COPYRIGHT Electronic Industries AllianceLicensed by Information Handling Services1 EIA 491 A2 m 32346
8、00 O073308 9 m EIA RECOMMENDED STANDARD RS-491 INTERFACE BETWEEN A NUMERICAL CONTROL UNIT AND PERIPHERAL EQUIPMENT EMPLOYING ASYNCHRONOUS BINARY DATA INTERCHANGE OVER CIRCUITS HAVING RS-423-A ELECTRICAL CHARACTERISTICS Prepared by IE-31 Committee on Numerical Control Systems and. Equipment -I- -. RS
9、-491 COPYRIGHT Electronic Industries AllianceLicensed by Information Handling Servicess E c T I o11 1. 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.7.1 1.7.2 1.8 2. 2.1 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.2.6 2.2.7 2.2.8 2.2.3 3. 4. 4.1 4 :2 4.2.1 4.2.2 4.3 4.3.1 4.3.2 4.3.3. 4.4 5. 5.1 5.2 5.3 5 . 3 1 5.3.2 5.3.3
10、 5.4 5.5 5 .G 6. 6.1 6.2 6.3 - EIA 491 82 m 3234600 0073309 O m RS-491 Table of Con tent6 PAGE SCOPE 2 Section Abstracts 2 Application 2 Classes of Service 2 Baud Rates 3 Bit Sequencing 3 Definition o$ Terms 3 E r r or Con d it ions 3 Error Detection 3 Error Recovery 3 Levels of Protocol 4 FUNCTIONA
11、L DESCRI PTIOFJ OF INTERCHANGE CIRCUITS 5 General Description 5 Circuit Definitions 5 Shield 5 Circuit SG - Signal Ground 5 Circuit TR - Terminal Ready 5 Circuit RS - Request to Send 5 Circuit RR - Receiver Ready 6 Circuit DP - Data i.lode 6 Circuit CS - Clear to Send 6 Circuit SD - Sencl Data 6 Cir
12、cuit RD - Receive Data 7 ELECTRICAL INTERFACE 8 IIECEANICAL INTERFACE 9 General Description 9 General Purpose Interface 9 Contact Assignments 10 Envi r onmen ta 1 I nt er f ace (Opt iona 1) 10 Connec tor 10 Contact Assignments 11 Contact Arrangeaent 1 1, Interconnection 12 LEVEL I PROTOCOL 15 Genera
13、l Description 15 Charcter Coding 15 Commun i cat i on s Con t r o 1 15 RS 15 15 16 cc End Condition Lec? d e r /T r a i 1 e r 16 End of Block 16 LEVEL II PROTOCOL 18 General Description 18 Character Coding 18 Communications Control Characters 18 Con ne c t: o r 9 Oper at ion 16 -11- - PROBLEM HARD C
14、OPL COPYRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesEIA 491 82 M 3234600 0071310 7 RS-491 SECTION 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.5 6.6 6.6.1 6.6.1.1 6.6.1.2 6.6.2 4.6.2.1 6.6.2.2 6.6.3 6.6.3.1 6.6.3.2 6.7 6.8 6.4 DC1 DC2 DC3 DC4 ES (optional) EOT DLE End
15、 o Block Leader/Trailer Protocol I In it ia t i on To Send Data To Receive Data Data Transmission Sending End Receiving Encl Sending End Receiving End Te r ni i na t i on Operation Initiate Timer 7. T ERH I NAL EI I U LAT ION 7.1 General Description 7.2 7.2.1 Data From The Numerical Control To The H
16、ost System 7.2.2 Data From The Host Cystern To The Numerical Control Commun ic a t i on C ha r a c t e r i st i cs APPEIIDIX A APPENDIX 13 . RELATED STAMDARDS AND BULLETINS PAGE 18 18 18 19 19 20 20 20 20 20 20 21 22 22 22 23 23 23 23 23 25 25 25 25 19. 25 26 27 29 PROBLEM HARD COPY I COPYRIGHT Elec
17、tronic Industries AllianceLicensed by Information Handling ServicesEIA 491 82 m 3234600 0071311i 9 m RS-491 Page 1 FOREWORD The infornation and connients contained in this foreword shall not be considered part of the standard. They have been included for clarification and guiclance. The increasing u
18、se 02 numerical controls and associated systens 2nd peripherals has focused attention on the need for a standardized interface. Based upon this need, the Electronic Industries Association has sponsored the standardization work done by Committee IE 31 on Numerical Control Systems and Equip;r,lent. Th
19、is connittee, nade up of repreqentatives of control builders, suppliers of program preparation systens and services, mcliine builders and users, has prepared this standard. The purpose of this standard is to define a common interface that will enable a user to connect numerical control equipment to
20、a plurality of peripheral devices including some full-duplex data communication equipment. A further purpose is to define a standard connector on the numerical control equipment and to assign contacts to the various circuit functions. EIA RS-423-A electricdl characteristics were chosen for the elect
21、rical interface. Although the majority of equipment presently uvailable uses the RS-232-C electrical interface, it was ielt that RS-422-A would eventually supercede it. The coimittee responsible for these standards recognized that there ould have io be a transitional period and provided RS-423 for t
22、hat purpose. ES-423-A is downward compatible with RS-232-C ancl at the same time upward compatible with RS-422-A. A seconci decision was to accomplish data copmunication using an asynchronous, character-oriented protocol. Although synchronous, bit-oriented protocols are expected to gain wider accept
23、ance iri the future, theyare more complex to implenent. It was felt that nost equipment making use of this standard would be better served by a sirlipler, and more familiar protocol. Other standards proposals, such as EIA SP-l3llilA, address more sophisticated applications. COPYRIGHT Electronic Indu
24、stries AllianceLicensed by Information Handling ServicesEIA 491 82 9 3234b00 0071312 O RS-491 Page 2 INTERFACE BETWEEN A NUMERICAL CONTROL UNIT AND PERIPHERAL EQUIPMENT EMPLOYING ASYNCHRONOUS BINARY DATA INTERCHANGE OVER . CIRCUITS HAVING RS-423-A ELECTRICAL CHARACTERISTICS (From EIA Standards Propo
25、sal No. 1292-A, formulated under the cognizance of EIA IE-31 Committee on Numerical Control Systems and Equipment.) 1. Scope 1.1 Section Abstracts This standard applies to the interconnection of a numerical control unit and a variety of peripheral devices including reader/punches, automatic send-rec
26、eive (ASR) terminals, intelligent terminals, part program preparation systems, or another numerical control unit using serial binary asynchronous transfer of data. The standard defines: Section 2 - Section 3 - Electrical Interface Functional Description of Interchange Circuits Section 4 - Mechanical
27、 Interface Section 5 - Level I Protocol Section 6 - Level II Protocol Section 7 - Terminal Emulation In addition, there are: Appendix A - Interim RS-232-C Implementations Appendix B - Glossary of Terms 1.2 Application This standard applies to point-to-point configurations where bit serialized asyn-
28、chronous communication is utilized, and primarily machine program (part program) data are being transferred. Applications transferring data other than RS-358-9 coded part programs are not precluded but are not specifically addressed by this standard. The transmission of all combinations of binary da
29、ta, however, is not within the scope of this standard. 1.3 Classes of Service Dedicated or switched four-wire operation is given consideration. The com- munication link hardware is full-duplex in that it must support transmission in both directions simultaneously. The data transfer is half duplex in
30、 that data is . transferred in only one direction at a time, except in the case of terminal emulation (see Section 7.2.1). COPYRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesEIA 493 82 3234600 0073333 2 m . RS-491 Page 3 1.4 1.5 1.G 1.7 *Baud Rates It is recornmended th
31、at numerical control equipment meeting., this standard support the commonly used baud rates of 11.15, - 300, 600, 128J, 2408, 4800, 9600, and 1920g. It is recornmended that provision should be made for different (split) input arid output baud rates to allow high speed. readers and low speed punches
32、to operate over the same communication circuit. Two stop bits are recommended for use with 110 baud; one stop bit is recommended for use, with all others. Bit Sequencing Characters are transmitted as a start bit, seven data bits with the least significant bit transmitted first, an even parity bit as
33、 defined in RS-358-B, followed by one or two stop bits. Additional information is provided in RS-404. Definition of Terms The definitions of terms used in this standard are in accordance with EIA Automation Bulletin 3C Glossary of Terms for Numerically Controlled Machines“. Additional terms are defi
34、ned in Appendix B. Err or Concl it i onc 1.7.1 Error Detection- Detection of transmission errors and retrgncmicsion for recovery from such errors are not within the scope of this standard. In the case of an interface to a ,tape reader, part programming center or other source of data, the numerical c
35、ontrol unit should perform a parity ttheck on the received data in accordance with RS-35843. SP131!J-A specifies an interface that provides error detection and retransmission. 1.7.2 Error Recovery This standard does .not include capabilities for the automatic correction of error conditions. If one s
36、ide of a communications link aborts a transfer, then the transfer is aborted reqarGless of the direction of the transfer. Manual intervention may be required to initiate a subsequent transfer . - y COPYRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesEIA 471 82 3234b 0071
37、314 4 m RS-491 Page 4 1.8 Level of Protocol This standard provides for a choice between two simple protocols. Level I protocol utilizes control signals on circuits separate from the data circuits for control of the link. Level II protocol utilizes a limited set of communication control characters tr
38、ansmitted over the data circuits for control of the link. The use of the DLE (Data Link Escape) control character in Level 2 protocol is not in accordance with ANSI X3.28-1978. EIA Standards Proposal No. 1310-A specifies an ANSI X3.28-based protocol utilizing a more comprehensive set of communicatio
39、n control characters and providing additional transmission capabilities. COPYRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesRS-491 Page 5 ,-i ,. EIA 493 82 3234600 0073335 b ,Functional Description of Interchange Circuits 2.1 General Description The interchanje circuits
40、 are a subset of EIA Standard RS-449 with a more specific meaning for each circuit defined herein. The ON and OFF states of the signals shall be implemented in accordance with RS 423-A (refer to -Section 4.1 - Generator Characteristics) . 2,2 Circuit Definitions 2.2.1 Shield A connector contact is a
41、ssicjned to facilitate the use of shielded interconnecting cable. This permits an external cable composed of tandem connectorized sections with continuity of shield accomplished by connection through this contact. The numerical control shall provide the shield connection and it is recommended that t
42、he peripheral device make no connection to this circuit. It is recognized that for certain e 1 e c t r orna g ne tic suppression situations, additional provisions may be necessary but are beyond the scope of this standard. interference 2.2.2 Circuit SG - Signal Ground This conductor directly connect
43、s the numerical control circuit ground to the peripheral device circuit ground, 2.2.3 Circuit TR - Terminal Ready 2.2.4 The signal on this circuit is suppliecl by the numerical control. The OW condition indicates that it is operational. Signals supplied by the numerical control on all other circuits
44、 shall not be considered valid unless TR is ON. This signal may be changed to an OFF condition during i transfer to indica,te the transfer is being aborted. Circuit RS - Request to Senil I The signal on this circuit is supplied by the numerical control. The ON condition indicates that the numerical
45、control is capable of communication in either direction. In level II protocol, it is not intended that this signal be changed from ON to OFF and then back to ON to _- Y COPYRIGHT Electronic Industries AllianceLicensed by Information Handling ServicesEIA 491 82 m 3234600 007131h 8 m RS-491 Page 6 sus
46、pend transmission 2.2.5 Circuit RR - 2.2.6 cesume communication . while a is in progress. Receiver Ready The signal on this circuit is supplied by the peripheral device. The ON condition indicates that it is operational. Signals on all other circuits supplied by the peripheral device shall not be co
47、nsidered valid unless RR is ON. If this signal goes to an OFF condition during a transfer, it indicates the transfer has been aborted. System dependent error recovery procedures should be invoked (such as notifying an operator). The signal on circuit RR is provided by the peripheral device which may
48、 be either the data receiving end or the data sending end. Circuit Diil - Data Mode The signal on this circuit is supplied by the peripheral device. The signal shall be in the Of? condition for communication to occur. This circuit is not required for all applications but some peripheral devices use
49、it. 2.2.7 Circuit CS - Clear to Send The signal on this circuit is supplied by the peripheral device. The 014 condition indicates that the peripheral device is capable of communication. in level 11, protocol it is not: intended that this signal be changed from Of1 to OFF and then back to ON to suspend and resume communication while a transmission is in progress. 2.2.8 Circuit SD - Send Data The signal on this circuit is supplied by the numerical control. 1.t is the actual data being commun ica t ed . Data shall be sent using asynchronous, 8-bit, charact
