Siemens SIMATIC ET 200AL, System Manual

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OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
Communication
Function Manual, 05/2021, A5E03735815-AJ
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Integrating the server method
The diagram below shows how an OPC UA client (A) calls the server method "Cool":
The CPU executes the instance "Cool1" of the server method "Cool" in the cyclic user program
⑥ .
The CPU first uses the instruction "OPC_UA_ServerMethodPre" to query ④ whether an OPC UA
client has called the server method "Cool" ① .
• If the server method has not been called, program execution returns directly to the cyclic
user program over ④ and ⑥ . The CPU resumes the cyclic user program after "Cool1".
• If the server method has been called, this information is returned to the server method
"Cool" over ④ . The actual functionality is now executed in the Cool server method,
see"<Method Functionality>" in the graphic.
The server method then uses the instruction "OPC_UA_ServerMethodPost"
⑤ to notify the
firmware (B) that the instruction has been executed ③ .
The firmware returns this information over ② to the calling OPC UA client (A).
The CPU resumes the cyclic user program after "Cool1".