Data Integrity

With IEC60870-5 protocol, a distinction is made between data transmission in the monitoring direction (status values, real values, discrete values) and in the control direction (commands and setpoints).

All data transmissions are acknowledged from the link communication level by the receiver. This acknowledgement is not sent to the sender of the data in every telecontrol link.

For data transmission in control direction, additional acknowledgement (e.g. ACTTERM) is possible. These acknowledgements are not sent by every telecontrol link either. For safe data transmission, it is necessary, in such cases, to configure data readback. The receiver then sends the data received back to the sender via the corresponding send blocks.

Information in the monitoring direction is acknowledged by the receiver on the lowest communication level (link level) when received. This acknowledgement is generated by the telecontrol head itself with some telecontrol heads. In the event of overload/overrun, a data message may be lost. For data in the control direction, so-called ACTTERM acknowledgement can be used. This additional acknowledgement is sent back to the sender when the data have been executed in the process. If data are to be sent in the monitoring direction with guaranteed transmission, it is necessary to read back the sent value via another variable and, after observing a monitoring time, resend in the event of an error.