Glossary
Term | Description |
|---|---|
substation, slave, server | Synonyms for a subordinate station (which is monitored) |
Central station, control station, master, client | 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 | Protocol data unit of the application layer (application protocol data unit) |
APCI | Protocol control information of the application layer (application protocol control information) |
ASDU | Service data unit of the application layer (application service data unit) |
IOA, address of the information object | Address of the single point, double point, etc. (information object address) |
primary station | The primary station sends commands (requests) to the secondary station and thus controls the data transfer of the secondary station. |
secondary station | The secondary station responds to requests from the primary station. |
Combined station | Combined stations can assume the role of primary station and secondary station (symmetric transfer, balanced mode). |
Symmetric transfer (balanced mode) | Both stations can act as primary or secondary stations and initialize the data transfer. |
Asymmetric transfer (unbalanced mode) | Data transfer is always initiated and controlled by the primary station. |