Siemens SIMATIC Operating Instructions Manual page 166

Glossary
Fail-Safe Systems
Fail-safe systems (F-systems) are systems that remain in a safe state or immediately switch
to another safe state when particular failures occur.
Fault Reaction Time
The maximum fault reaction time for an F-system is the time between the occurrence of a
fault and a safe response at all affected fail-safe outputs.
For -> F-systems in general: The maximum fault reaction time is the time between the
occurrence of any fault in any -> F-I/O and the safe response at the associated fail-safe
output.
For digital inputs: The maximum fault reaction time is the time between the occurrence of the
fault and the safe response on the backplane bus.
For digital outputs: The maximum fault reaction time is the time between the occurrence of
the fault and the safe response at the digital output.
F-CPU
An F-CPU is a central processing unit with fail-safe capability that is permitted for use in
S7 Distributed Safety/S7 F/FH Systems.
For S7 F/FH Systems, the F-copy license allows the central processing unit to be used as an
F-CPU. In other words, it can execute a -> safety program.
For S7 Distributed Safety, an F-copy license is not required. A -> standard user program can
also be run in the F-CPU.
F-I/O
F-I/O is a group designation for fail-safe inputs and outputs available in SIMATIC S7 for
integration in S7 Distributed Safety and S7 F/FH System F-systems. The following F-I/O
modules are available:
● Fail-safe I/O module for ET 200eco
● S7-300 fail-safe signal modules (F-SMs)
● Fail-safe modules for ET 200pro
● Fail-safe modules for ET 200S
● Fail-safe DP standard slaves
● Fail-safe I/O standard devices
F-Monitoring Time
-> PROFIsafe Monitoring Time
F-Systems
-> Fail-Safe Systems
166
ET 200pro Distributed I/O System - Fail-Safe Modules
Operating Instructions, 05/2007, A5E00394073-02