ABB Rellon 620 Series, Руководство по протоколу связи

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Section 2
1MAC306892-MB C
IEC 60870-5 overview
10 RER620
Communication Protocol Manual
2.2.1 Unbalanced transmission
When using unbalanced transmission, the controlling station controls the data traffic by
polling the controlled outstations sequentially. In this case, the controlling station initiates
all the message transfers while the controlled outstations can transmit only in response to
the message from the controlling station.
Table 2: Supported transmission services initiated by the controlling station
2.2.2 Balanced transmission
When using balanced transmission, each station can initiate message transfer. The stations
may act simultaneously as controlling stations and controlled outstations. Therefore they
are called combined stations. In this manual, a combined station is called either a
controlling station or a controlled outstation according to its function in the message
exchange.
The balanced transmission is restricted to point-to-point and to multiple point-to-point
configurations.
The balanced transmission supports SEND/CONFIRM and SEND/NO REPLY
transmission services. The SEND/NO REPLY transmission service can be initiated only
by a controlling station with a broadcast address in a multiple point-to-point configuration.
2.3 Basic application functions
2.3.1 Data acquisition
The data delivered by a controlled outstation can be replies to commands or process values
which are collected cyclically, upon change, or upon request from the controlling station.
All the data is buffered in the controlled outstation because the data may appear faster than
the communication link is able to transfer it to the controlling station.
When unbalanced transmission is used on the link layer, the buffered data must be polled
by the controlling station. The controlled outstation must always wait for a request for
transmission from the controlling station.
When balanced transmission is used on the link layer, the buffered data is transmitted by
the controlled outstation to the controlling station without a delay.
Service Purpose
SEND/NO REPLY For global messages and for cyclic set-point commands from the
controlling station
SEND/CONFIRM For control commands and set-point commands from the controlling
station
REQUEST/RESPOND For polling data from the controlled outstations