Glossary
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05
Glossary-3
Custom F-Libraries
F-libraries created by the user containing F-FBs, F-FCs, and application templates (network
templates).
Dark Period
Dark periods occur during switch-off tests and during complete bit pattern tests. Test-related
0 signals are switched from the fail-safe output module to the output bit while the output is
active. The output is then switched off briefly (dark period). A sufficiently slow actuator does
not respond to this and remains switched on.
Deactivated Safety Mode
Deactivated safety mode refers to the temporary deactivation of -> safety mode for test
purposes, commissioning, etc.
Whenever safety mode is deactivated, the safety of the system must be ensured by other
organizational measures, such as operational monitoring and manual safety shutdown.
Depassivation
-> Reintegration
Discrepancy Analysis
Discrepancy analysis for equivalence or non-equivalence is used for fail-safe inputs to detect
errors based on the timing of two signals with the same functionality. The discrepancy
analysis starts when different levels (when checking for non-equivalence: the same level) are
detected for two related input signals. A check is made to determine whether the difference
(when checking for non-equivalence: the match) has disappeared after expiration of a
specified time known as the discrepancy time. If not, this means that a discrepancy error
exists.
There are two types of discrepancy analyses for fail-safe input modules:
•
In the case of -> 1oo2 evaluation:
The discrepancy analysis is carried out between the two input signals of the -> 1oo2
evaluation in the fails-safe input module.
•
In the case of redundant I/O (S7 FH systems only):
The discrepancy analyses is carried out between the two input signals of the redundant input
modules by the fail-safe driver blocks of the
S7 F Systems optional software.
Discrepancy Time
Discrepancy time is a period of time assigned for the -> discrepancy analysis. If the
discrepancy time is set too high, the fault detection time and the -> fault reaction time are
extended unnecessarily. If the discrepancy time is set too low, availability is decreased
unnecessarily because a discrepancy error is detected when, in reality, no error exists.
