Siemens SIMATIC ET 200AL, System Manual

Page: 1470 / 2255

OPC UA communication
9.4 Using the S7-1500 CPU as an OPC UA client
Communication
Function Manual, 05/2021, A5E03735815-AJ
349
Order of the OPC UA instructions
The following figure shows the order in which the OPC UA instructions are called in a user
program in order to use these instructions to read or write PLC tags:
① Instructions for preparation of read and write operations
② Read and write instructions
③ Instructions for "clean-up" after a completed read or write operation
The "OPC_UA_NodeReleaseHandleList" instruction can be omitted if "OPC_UA_Disconnect" is
called immediately afterwards.
Figure 9-75 Call sequence for write and read operations
STEP 7 (TIA Portal) automatically supplies the parameters of these instructions if you are
using a client interface and a configured connection to an OPC UA server.
The procedure is shown in the following section.
Using a client interface and configured connection
To use a configured OPC UA connection, follow these steps:
1.
Open your user program in the TIA Portal.
2. Using drag-and-drop, move the " UA_Connect " instruction into the program editor.
You will find the instruction under "Instructions > Communication > OPC UA" in the TIA
Portal.