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Additional settings as well as features and what you need to know about the RFC 4072S
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7.7 Substitute value behavior for PROFINET devices
and PROFIsafe F-Devices
The substitute value behavior for the input data of the controller must be specified in your
PLCnext Engineer project. By default, the input data of the RFC 4072S is set to zero if the
connection to a PROFINET device is interrupted.
Set the substitute value behavior for each PROFINET device individually in
PLCnext Engineer (see Figure 7-12 ).
Figure 7-12 PROFINET device – “Substitute value behavior of inputs”
If the connection to a PROFINET device is interrupted, the “Set to zero” option means that
the corresponding input data of the controller is set to zero. The “Keep values” option means
that if the connection to a PROFINET device is interrupted, the input values that were valid
immediately before the interruption are present as the input data in the application program.
When the connection to the PROFINET device is restored, the substitute values remain
valid as input data until the PROFINET device has been started up completely. Once the
connection has been established again, the latest input data is used.
Note on the substitute value behavior for F-Devices
Observe the following when programming/configuring the safety logic:
– Switching from the safe state (substitute value = 0) to the operating state can gener-
ate an edge change (zero/one edge).
– In the safety logic, take measures to prevent this edge change resulting in unexpected
machine/system startup or restart.