Siemens SIMATIC ET 200SP System Manual page 259

Fault tolerance time
The fault tolerance time of a process is the time a process can be left unattended without risk
to life and limb of the operating personnel, or damage to the environment.
Any type of F-system control is tolerated within this fault tolerance time, i.e. the → F-system
can control its processes incorrectly or even not at all. The fault tolerance time depends on
the type of process and must be determined on a case-by-case basis.
F-CPU
An F-CPU is a central processing unit with fail-safe capability that is permitted for use in
SIMATIC Safety. A standard user program can also be run on the F-CPU.
F-I/O
Collective name for fail-safe inputs and outputs available in SIMATIC S7 for integration into
the SIMATIC Safety F-system. Available F-I/O modules:
● Fail-safe I/O module for ET 200eco
● Fail-safe signal modules S7-300 (F-SMs)
● Fail-safe modules for ET 200S
● Fail-safe modules for ET 200SP
● Fail-safe DP standard slaves
● Fail-safe PA field devices
● Fail-safe IO devices
Firmware update
Upgrade of firmware for modules (interface modules, I/O modules etc.), e.g. after function
extensions, to the newest firmware version (update).
F-monitoring time
→ PROFIsafe monitoring time
F-Systems
→ fail-safe systems
Functional ground
Functional ground is a low-impedance current path between electric circuits and ground. It is
not designed as a safety measure but instead, for example, as a measure to improve
interference immunity.
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF
Glossary
259