Siemens SIMATIC S7 CP340 Programming Manual page 66

5 MODBUS RTU Protocol communication
Set "Monitoring Time for"  "Transfer of parameters to modules(100ms)" to a
value as small as 1000 (=100s), by which an adequately long time may be
guaranteed to download the used load protocol driver into the CP card during the
parameter assignment process.
5.4.3 Write communication program
1. Double-click OB1 to open the programming screen. Invoke FB180 in Libraries -
> Modbus, and distribute instance data block DB180. The function code
communication data DB1 and DB2 for the newly created data block FC03 06 16
and FC04 are both in 50-word array structure.
Fig. 121: Communication data block DB1 and DB2
CP340/CP341/CP440/CP441 Communication and Programming
Entry-ID: 88867653, V1.0, 02/2014
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