Glossary
Term | Description |
---|---|
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 other 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 answers to the requests of the primary station. |
combined station | Combined stations can act as primary and secondary station (balanced mode). |
balanced mode | In balanced mode both stations act as primary and secondary stations and can 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. |