The safety function requires that fail-safe values (safe state) be applied to the fail-safe
module instead of process values (passivation of the fail-safe module) in the following
situations:

• When the F-system is started up
• If errors are detected during safety-related communication between the F-CPU and the Fmodule via the PROFIsafe safety protocol (communication error).
• If fail-safe I/O or channel faults occur (for example wire break, discrepancy error)
  

Faults detected are entered in the diagnostic buffer of the F-CPU and reported to the safety program in the F-CPU.
F-modules cannot save errors as retentive data. When the system is powered down and then restarted, any faults still existing are detected again during startup. However, you have the option of saving faults in your safety program