Siemens SIMATIC S7-1200

Communication processor and Modbus TCP
13.8 Legacy Modbus TCP communication
S7-1200 Programmable controller
1268 System Manual, V4.2, 09/2016, A5E02486680-AK
13.8.4.5
Example: Legacy MB_CLIENT 4: Coordinating multiple requests
You must ensure that each individual Modbus TCP request finishes execution. This
coordination must be provided by your program. The example below shows how the outputs
of the first and second client requests can be used to coordinate execution.
The example shows both clients writing to the same memory area. Also, a returned error is
captured which is optional.
Network 1:
Modbus function 3 - Read holding register words
Network 2:
Modbus function 3 - Read holding register words