Siemens SIMATIC PCS 7 Operating Manual page 116

Configuring the safety program
7.7 Passivation and reintegration of input/output channels
Result
If the value 6 is written to the "IN" input of the F_QUITES block, followed by the value 9
within 60 seconds, the "OUT" output of F_QUITES is set to 1 for one cycle. The F-channel
drivers connected to this output (at the "ACK_REI" input) are reintegrated if they are ready
for acknowledgment (ACK_REQ = 1).
If the acknowledgment prompt is no longer pending, the buttons on the OS are hidden again.
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Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB