Software architecture

You do not need to know the internal software architecture of this product to use it, but it may be of interest in some cases. We will therefore briefly present it to you below.

The TwinCAT OPC UA Client essentially consists of the following components:

• The process in the operating system
• The communication driver in real-time
• The TwinCAT XAE extension
• The PLC library

The interaction of the individual components is described in more detail in the following diagram:

Process in the operating system

The process in the operating system (TcOpcUaClient.exe) takes care of the OPC UA protocol functions and makes them available via an ADS server so that the TwinCAT real-time components (e.g. the driver or the PLC library) can access them.

Communication driver in real-time

The driver in real-time is responsible for the communication of the I/O device with the process in the operating system. It converts the configured process data into ADS telegrams, which are exchanged with the process in order to be converted into OPC UA commands. There is an engineering component in TwinCAT XAE for the configuration of the communication connection and the choice of data points.

TwinCAT XAE Extension

The engineering component in TwinCAT XAE provides a graphical configuration interface for the I/O device. This means that variables can be read from OPC UA servers and added to the process image so that they can be processed later at runtime.

PLC library

The PLC library provides the OPC UA functions of the process in the operating system for the PLC logic. Similar to the driver, the PLC library communicates with the process via ADS in order to access the OPC UA functions.