Siemens Second Wind Function Manual page 62

Configuration
4.4 S7 Distributed Safety
Unwanted restart of the plant after acknowledgment of a communication error
The plant cannot be automatically restarted after a communication error on the HMI device
is acknowledged.
Therefore, ensure that your safety program requires an additional user action before the
plant can be restarted.
Interconnection of the F FBs
The blocks are interconnected with one another and with the process image of the Mobile
Panel 277F IWLAN.
For every Mobile Panel 277F IWLAN, there is a memory area in the PLC that is commonly
access by the HMI device and the PLC, the so-called process image. The signal sates of the
HMI device's inputs is sent to the PLC at the start of the cyclic control program through the
process image of the inputs, PII. The process image of the outputs, PIQ, is sent to the HMI
device as the signal state at the end of the cyclic program.
The following figure is a schematic representation of the interconnection of F FBs to one
another and to the PII and PIQ.
You cannot directly evaluate the PII and PIQ in your program.
62
WARNING
WARNING
Fail-safe operation of the Mobile Panel 277F IWLAN
Function Manual, 08/2008, 6AV6691-1FQ01-2AB0