Siemens SIMATIC ET 200SP System Manual page 264

Glossary
Redundancy, safety-enhancing
Multiple availability of components with the aim of exposing hardware faults based on
comparison; such as → 1oo2 evaluation in → fail-safe modules.
Reference identification
In accordance with EN 81346, a specific object is clearly referenced in relation to the system
to whose components the object belongs. Thus, unique identification of the modules in the
entire system is possible.
Reference potential
Potential from which the voltages of the participating circuits are considered and/or
measured.
Reintegration
After the elimination of a fault, it is necessary to ensure the reintegration (depassivation) of
the → F-I/O. Reintegration (switchover from fail-safe values to process values) occurs either
automatically or only after a user acknowledgment in the safety program.
In the case of a fail-safe input module, the process values pending at the fail- s afe inputs are
made available to the s afety program again after reintegration. In the case of a fail-safe
output module, the → fail-safe system transfers the output values in the safety program to the
fail-safe outputs again.
Safe state
The basic principle of the safety concept in F-systems is the existence of a safe state for all
process variables. For the digital F-I/O, for example, the safe state is the value "0".
Safety class
Safety level (Safety Integrity Level) SIL according to IEC 61508:2010. The higher the Safety
Integrity Level, the more rigid the measures for prevention of systematic faults and for
management of systematic faults and hardware failures.
The fail-safe modules support operation in safety mode up to safety class SIL3.
Safety frame
In safety mode, data are transferred between the → F-CPU and → F-I/O in a safety frame.
Safety function
A mechanism integrated in the → F-CPU and → F-I/O that enables their use in → the fail-safe
system SIMATIC Safety.
According to IEC 61508:2010: A safety function is implemented by a safety system in order
to maintain or force a system safe state in the event of a specific fault.
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Distributed I/O system
System Manual, 12/2015, A5E03576849-AF