Communication

The communication protocols OPC UA; Modbus TCP; MQTT; and ADS are all used together to transfer information relating to the values of symbols and structures of the PLC.

In contrast to BACnet, they do not describe any standardized communication objects, meaning that the structure of the data in many projects is very specific and individual. Independent of BACnet, TwinCAT TF8040 is also very helpful for such projects, as the Tc3_BA2 basic library contains a large number of function blocks that are required for a building automation project regardless of the communication protocol used.

The BACnet communication protocol has become the global standard for building automation. In contrast to the other protocols, BACnet provides a very detailed standard with its objects and services.

TwinCAT Building Automation makes use of the object-oriented structure of BACnet.

The library Tc3_XBA contains a framework called the base framework.

It is used to map a project structure and numerous other generic functions.

The Site Server within the PLC organizes the ADS communication to the TwinCAT HMI.

The Site API is the counterpart of the Site Sever and realizes the generic representations in the HMI.

The Site Explorer service tool also communicates with the automation stations using the Site API via ADS.