1、A* .EuROPEANsIANDARD NORME EUR0PEE”E EUROP- NORM 3404583 0099379 298 EN o870-52 September 1993 UDC 621.398 : 621.316.1 : 681.3.04 Descriptors: Teleprocessing, control processes, telecontrol, data transmission, open system interconnection, data transmission procedure, data rnukihk procedure, protocol
2、, data structure, frame English veision Telecontrol equipment and systems Part 5: ?k.ansmission protocols Section 2: Link transmission procedures (IEC 870-52 : 1992) Matriels et Systemes de tlconduite Femwirkeinrichtungen und Fernw yLksysteme Teil 5 erhagmgprotokolle Partie 5 protocoles de transmiss
3、l on Section 2 Procdures de transmission de liaison Hauptabschnitt 2: aertragungsprozeduren der de donnes Verbindungsducht (CEX 87052 : 1992) C 87052 : 1992) This European Standard was approved by CENELEC on 19934746. CENELEC members are bound to comply with the CEN/CENELEC internal Regulations whic
4、h stipulate the conditions for giving this European Standard the status of a national stanard without any alteration. Upto-date lists and bibliographicai references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European St
5、andard exists in three official versions (English, French, German). A veision in any other ianguage made by translation under the responsibility of a CENELEC member into its own language and notied to the Centrai Secretariat has the same status as the official versions. CENELEC members are the natio
6、nal electrotechnicd committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugd, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisat
7、ion Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1060 Brussels O 1993 Copyright reserved to CENELEC members Ref, No. EN 6087052 : 1993 E Foreword The CENELEC questionnaire procedure, performed for nding out whether or not the Intrnation
8、al Standard IEC 87W2 : 1992 could be accepted without textual changes, has shown that no common modicaons were necessary for the acceptance as European Standard. The reference document was submitted to the CENELEC members for formal vote and was approved by CENELEC as EN 6087052 on 6 July 1993. The
9、following dates were xed: - latest date of publication of an identicai national standard (dop) 19940801 - latest date of withdmwal of conflicting national standards (dow) 1994-0801 _- 1 3404583 0099380 TOT Annexes designated normative are part of the body of the standard. in this standard, annexes A
10、 and ZA are normative. i .- = 3404583 0099383 946 870-5-2 O IEC INTRODUCTION This section of IEC 870-5 is pari of a series which highlights specific requirements and conditions for data transmission in telecontrol systems and describes ways to meet those requirements. In terms of the OS1 (Open Syste
11、m Interconnection) reference model of SO-CCITT, which subdivides communication into seven layers, this section is concerned with the procedures required by the second layer: the link layer. Section 1 covers the two bottom layers: the physical layer and the link layer, the latter being explained in t
12、erms of admissible frame formats and rules for frame synchronization. This section specifies standard link transmission procedures which operate on the link layer. 870-5-2 O IEC TELECONTROL EQUIPMENT AND SYSTEMS Part 5: Transmission protocols Section 2: Link transmission procedures 1 scope and objec
13、t 1.1 Scope This section of IEC 870-5 applies to telecontrol equipment and systems with coded bit serial data transmission for monitoring and controlling geographically widespread processe s. The defined link procedures are restricted to message transmission sequences operating with size 1 windows.
14、This means that the link layer of the primary station (station that initiates a message transfer) accepts a request for a new message transfer only when a previously accepted request for a message transfer is terminated either successfully or with an error indication. The procedures are applicable t
15、o balanced and unbalanced trans- mission in telecontrol systems using half duplex or duplex transmission channels. 1.2 Object The standard transmission procedures defined by this section are applicable to point-to- point, multiple point-to-point, multipoint-star, multipoint-partyline and multipoint-
16、ring configurations as described in 4.4 of IEC 870-1-1. The data transmission functions in these systems are composed of three basic types of link transmission services, namely: 1. SEND/NO REPLY 2. SENDICONFIRM 3. REQUEST/RESPOND The two services SENDICONFIRM and REQUEST/RESPOND consist of a sequenc
17、e of non-separable dialogue elements between requesfing stations and responding stations. The protocol defined in this section accepts and processes only a single link trans- mission service at a time in each direction of a bidirectional communication system. Each transmission service is terminated
18、either successfully or with error reports before the next transmission service begins. This means that the window size for successive packet transfers is 1 and the specified error recovery for the transmission services SENDICONFIRM and REQUEST/RESPOND utilize the stop-and-wait method for automatic r
19、epeat requests (ARQ). 2 = 3404583 0099335 Tbb 870-5-2 O IEC In point-to-point configurations equipped with duplex channel operation. the defined protocol supports balanced transmission procedures, that is simultaneous data trans- mission services in both directions of the communication link. This en
20、ables outstations to report spontaneous events to the control station as they occur, without having to be polled. This reduces reporting delays and leads to faster data acquisition. However, the use of an individual duplex communications channel to each outstation leads to increased equipment costs.
21、 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this section of IEC 870-5. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this
22、section of IEC 870-5 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 50(371): 1984, International Electrotechnical Vocabulary (IEV) - Chapter
23、 371: Tele- control. IEC 870-1 -1 : 1988, Telecontrol equipment and systems - Part 7: General considerations - Section one: General principles. IEC 870-5-1 : 1990, Telecontrol equipment and systems - Pat7 5: Transmission protocols - Section One: Transmission frame formats. 3 Formats and structures o
24、f standard transmission frames The transmission procedures defined in this section provide protection against resi- dual (.e. undetected) transmission errors in the range of integrity class Il, specified in IEC 870-5-1, if the transmission frame format FT 1.1 is used and if the transmission rules sp
25、ecified by that section are observed. Residual transmission errors in the range of integrity class 12 are achieved if one of the transmission frame formats FT 1.2, FT 2 or FT 3, specified by that section, are utilized and if the corresponding transmission rules are observed. Only one chosen transmis
26、sion frame format may be used on any given physical communications channel in a system. The order of fields in the frames is generally as follows: Length (one octet) Control (one octet) Address (one or more octets, by agreement) Link user data (n octets) 870-5-2 O IEC 3.1 Format FT t. 1 User data Fr
27、ame with variable length Frame with fixed length (Note 1) (Note 2) Single character (called single control character in IEC 870-5-1) L: length field range: 0.127 L specifies the number of subsequent user data octets including the control and address fields C: control field A: address field, optional
28、 NOTES 1 2 The unshaded fields are the user data of the frame as indicated in IEC 870-5-1. There is no special frame with a fixed length; the variable length frame is used in all cases. The shaded fields have already been defined in IEC 870-5-1. ! 4 a 870-5-2 O IEC Link user data 3.2 Format FT 1.2 (
29、Note 1) User data Frame with variable length II A I (Notes 1 and 4) (Note _I 3) Frame with fixed length . . A . /;,swcf$i; ; . i.: . . ; Link user (Note 1) W 3404583 0099337 839 Single character (called single control character in IEC 870-5-1) (Note 1) (Notes 1 and 2) +I I L: length field range: 0.2
30、55 L specifies the number of subsequent user data octets including the control and address fields C: control field A: address field. optional NOTES 1 bits with weights 27 _ 2 denote the left hexadecimal character and bits with weights 23 . 20 denote the right hexadecimal character, Specified data oc
31、tets are represented in hexadecimal notation, in which O110 lo00 - 68 e.g.: 68 H t - The sequence of bit transmission begins. as defined in IEC 870-5-1. with the least significant bit 20. 2 3 4 The unshaded fields are the user data of the frame as indicated in IEC 870-5-1 Reserved for special use by
32、 agreement. A fixed number of user data octets is specified per system. The shaded fields have already been defined in IEC 870-5-1. . . 3404583 0099338 775 870-5-2 O I EC 3.3 Format FT 2 Frame with variable length Frame with fixed length Single character (called start character 2 in IEC 870-5-1) (No
33、tes 1 and 3) (Note 1) (Note 1) l+l data User Link (Note 2) User data LPO C A Link user data (Note 2) (Note L: length field range: 0.255 L specifies the number of subsequent user data octets including the control and address octets and excluding the CRC-check octets L = O specifies a fixed frame leng
34、th with at least 2 user data octets L O specifies a variable frame length with L user data octets C: control field A: address field, optional CRC-check: Cyclic Redundancy Check NOTES 1 0010 o111 e.g. 27H P - - 2 7 The sequence of bit transmission begins, as defined in IEC 870-5-1. with the most sign
35、ificant bit. Specified data octets are represented in hexadecimal notation, 2 Up to 15 user data octets are completed by a CRCcheck octet (see IEC 870-5-1. subclause 6.2.4.3.1. R3). 3 The unshaded fields are the user data of the frame as indicated in IEC 870-5-1. The shaded fields have already been
36、defined in IEC 870-5-1. 6 I 3404583 0099339 bol 1 870-5-2 O IEC 3.4 FormatFT3 Frame with variable length Link user (Note 2) data Frame with fixed length User ttri (Notes 1 and (Note i) User data data I I Link I 3) i ICI . 1.1 /IF1 user (Note 1) (Note 1) (Note 2) (Note 2) (Note 2) Single character (c
37、alled ?start character 2? in IEC 870-5-1) . (Note 1) (Note 1) L: length field range: 0.255 L specifies the number of subsequent user data octets including the control and address octets and exclud- ing the CRC-check octets L = O specifies a fixed frame length with at least 2 user data octet L O spec
38、ifies a variable frame length with L user data octets C: control field A: address field, optional CRC-check: Cyclic Redundancy Check NOTES 1 Specified data octets are represented in hexadecimal notation. 0110 O100 64Hz-p 64 oooo O101 e.g. 05H I - - o5 The sequence of bit transmission begins, as defi
39、ned in IEC 870-5-1. with the most significant bit. 2 Up to 16 user data octets are completed by a CRC-check octet (see IEC 870-5-1. subclause 6.2.4.4.1. R3). 3 The unshaded fields are the .user data? of the frame as indicated in IEC 870-5-1 The shaded fields have already been defined in IEC 870-5-1.
40、 . -. ! 3404583 0099340 323 , b .SEND (D) SENDI NO REPLY (SI 1 870-5-2 O IEC IN0 (D) b 4 Service primitives and elements of transmisslon procedures The data communication is described by “service primitives“ crossing the interface between the service user and the link layer, and associated of the li
41、nk between communicating stations, “transmission procedures“ RESPOND (S3) CON (D) 4 D = data The contents of the service primitives (parameters, conditions, etc.) are not standardized in this section. RESP (D) RE-4 1 TIME I I I Service Link Link transmission procedures Service primitives REQ ID) I L
42、ink layer Sei Service user BS I REQ I I IN0 REQUEST/ b Figure 1 - Relationship between service primitives and transmission procedures for basic link services 8 i W 3404583 0099343 2bT W I 870-5-2 O IEC Figure 1 shows error free transmission procedures of basic link services. Transmission errors are
43、only detected by receiving stations. A secondary station receiving a disturbed SEND or REQUEST frame does not reply. This is detected by the primary station timing out, because the expected CONFIRM or RESPOND frame is not received. Also a primary station receiving a disturbed CONFIRM or RESPOND fram
44、e ignores it and consequently detects the error. There are four types of primitives that may contain user data and sets of parameters and condit ions, namely: request primitive REO: a request issued by the service user to invoke some procedure in the link layer; confirmation primitive CON: a confirm
45、ation issued by the link layer to complete the procedure previously invoked by a request; a indication issued by the link layer to announce the wish to deliver data to the service user, or to invoke some service user procedure; indication primitive IND: response primitive RESP: a response issued by
46、the service user to an- nounce the completion of a procedure previously invoked by an indication. NOTE - Confirmations or responses can be positive or negative. as appropriate to the circumstances. Typical contents of the service primitives are parameters, conditions and user data as fo Ilow s : use
47、r data; types of transmission service (function code, e.g. SEND/CONFIRM); negative/positive confirmations or responses; DFC (data flow control); ACD (access demand); number of repetitions (e.g. 3); error status (e.g. after a repeated transmission error); status of the layer (e.g. restart conditions)
48、. 4.1 SENDINO REPL Y service 4.1 .l Service primitives - Primary station The link layer accepts the request primitive REQ (SEND/NO REPLY) given by the link user when it is able to transmit the message. If the link layer is not able to transmit the message (disconnection from line or error state) a n
49、egative Confirmation primitive CON (negative, SEND/NO REPLY, error status) is returned. 870-5-2 O IEC - Secondary station An indication primitive IND (no response required) announces the reception of the message to the service user of the secondary station. 4.1.2 Transmission procedure The specified SEND frame (see tables 1 and 3) is transmitted when the transmission pro- cedure of a previous service is terminated After the transmission of the frame a line idle interval is provided whose length is specified as an interval between frames upon dete
