Deactivating and reactivating a Profibus-DP slave with Siemens PLC S7

Question:

How can a Profibus-DP slave (eg. EMF 2133, E82ZAFPC) be deactivated and reactivated from the PLC program of a Siemens S7?

Answer:

Deactivating and reactivating a Profibus DP slave is useful for example if individual controllers are to be disconnected from the mains and the communication modules are not supplied externally with 24V. In this case, the Profibus master would recognise that the slave devices are no longer available on the bus and the PLC would change to the STOP state.

It is possible to integrate error organisation modules (OBxx) into the PLC program so that the PLC no longer changes to the STOP state. The bus cycle time increases however, if the planned slaves are not available because the Profibus master tries to call these slaves repeatedly. For this case, the PLC offers an additional Siemens function SFC 12. SFC 12 is used to deactivate and reactivate a Profibus slave. A deactivated slave is no longer called by the Profibus master.

Further information on SFC 12 can be obtained from the Siemens documentation or online help of STEP7.

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