Glossary
Term |
Description |
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substation, slave, server, controlled station |
Synonyms for a subordinate station (which is monitored) |
central station, master, client, controlling station |
Synonyms for a higher-level station (control station, monitors others stations) |
control direction |
Data transfer direction from the central station to the substation |
monitoring direction |
Data transfer direction from the substation to the central station |
application objects |
IEC information objects in the TwinCAT PLC application (single points, double points, measured values, short floating point values etc.) |
APDU |
Application protocol data unit |
APCI |
Application protocol control information |
ASDU |
Application service data unit |
IOA, information object address |
Address of the single point, double point, measured value, short floating point value etc. |
primary station |
Primary station sends commands/requests to the secondary station and controls the data transmission of the secondary station. |
secondary station |
Secondary station anwers to the requests of the primary station. |
combined station |
Combined stations are able to act as primary and secondary station (balanced mode). |
balanced mode |
In balanced mode both stations act as primary and secondary stations and are able to initialize the data transmission. |
unbalanced mode |
In unbalanced mode only the primary station is able to initialize the data transmissions. The central station acts as primary station and the substation acts as secondary station. |
CAA |
Common ASDU address |
COT |
Cause of transfer |
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