Siemens SINUMERIK MC Commissioning Manual page 92

Safety program of the F-PLC
3.15 Data exchange between the standard user program and safety program
Also note that the clock memory, which you defined under tab "Properties" when configuring
the F-CPU, can change during the runtime of the F-runtime group. This is because the clock
memory runs asynchronously to the F-CPU cycle.
Note
If this is not complied with, then the F‑PLC can go into STOP. The cause of the diagnostic result
is entered in the diagnostics buffer of the F-PLC.
92
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB