This Standard applies to telecontrol equipment and systems with coded bit serial data transmission for monitoring and controlling geographically widespread processes.
The defined link procedures are restricted to message transmission sequences operating with size 1 windows. 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 to balanced and unbalanced transmission in telecontrol systems using half duplex or duplex transmission channels.
The standard transmission procedures defined by this Standard are applicable to point-to-point, multiple point-to-point, multipoint-star, multipoint-partyline and multipoint-ring configurations as described in 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) SENDEONFIRM
3) REQUEST/RESPOND
The two services SENDZONFIRM and REQUEST/RESPOND consist of a sequence of non-separable dialogue elements between requesting stations and responding stations.
The protocol defined in this Standard accepts and processes only a single link transmission service at a time in each direction of a bidirectional communication system. Each transmission service is terminated 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 SENDKONFIRM and REQUEST/RESPOND utilize the stop-and-wait method for automatic repeat requests (ARQ).
In point-to-point configurations equipped with duplex channel operation, the defined protocol supports balanced transmission procedures, that is simultaneous data transmission services in both directions of the communication link. This enables 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.
2 Normative References
The following standards contain provisions which, through reference in this text, constitute provisions of this Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below.
GB/T 18657.1-2002 Telecontrol equipment and systems — Part 5:Transmission protocols — Section 1: Transmission frame formats (idt IEC 60870-5-1:1990)
IEC 50(371):1984 International Electrotechnical Vocabulary (IEV) — Chapter 371: Telecontrol
IEC 870-1-1:1988, Telecontrol equipment and systems — Part 1: General considerations — Section one: General principles
GB/T 18657.2-2002 The following standards are cited：
