Siemens SIMATIC ET 200S Installation And Operating Manual page 178

Glossary
Fault Response Time
The maximum fault response time for an F-system is the time between the occurrence of any
fault and a safe response at all affected fail-safe outputs.
For -> F-Systems in general: The maximum fault response time begins with the occurrence
of any fault in any -> F-I/O module and ends with a safe response at the associated fail-safe
output.
For digital inputs, The maximum fault response time begins with the occurrence of the fault
and ends with the safe response on the backplane bus.
For digital outputs, The maximum fault response time begins with the occurrence of the fault
and ends with the safe response at the digital output.
Fault Tolerance Time
The fault tolerance time of a process is the time interval during which the process can be left
on its own without risk to life and limb of the operating personnel or damage to the
environment.
Within the fault tolerance time, any type of F-system process control is tolerated. That is,
during this time, the -> F-system can control its process incorrectly or it can even exercise no
control at all. The fault tolerance time depends on the process type 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
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 on 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 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 200S
• Fail-safe DP standard slaves (for S7 Distributed Safety only)
F-Systems
-> Fail-safe systems
Module Fault
Module faults can be external faults (for example, missing load voltage) or internal faults (for
example, processor failure). An internal fault always requires module replacement.
Glossary-4
ET 200S Distributed I/O System - Fail-Safe Modules
Hardware Installation and Operating Manual, 07/2005, A5E00103686-04