Siemens PM-E F pm DC24V PROFIsafe Installation And Operating Manual page 211

CRC signature
The validity of the process values in the safety message frame, the accuracy of the assigned
address references, and the safety-related parameters are validated by means of the CRC
signature in the safety message frame.
Dark period
Dark periods occur during shutdown tests and complete bit pattern tests. The fail-safe output
module switches test-related zero signals to the active output. This output is then briefly
disabled (= dark period). An -> actuator with sufficient lag does not respond to these signals
and remains switched on.
Discrepancy analysis
The discrepancy analysis for equality/non-equality is used at fail-safe inputs to detect errors
based on the timing of two signals with the same functionality. Discrepancy analysis is
initiated when different levels (when testing for nonequivalence: same voltage levels) are
detected at two associated input signals. The signals are checked to determine whether the
difference (when checking for nonequivalence: the consistency) has disappeared within a
programmable period known as the -> discrepancy time. If not, this means that a
discrepancy error exists.
The discrepancy analysis compares the two input signals of the 1oo2 sensor evaluation in
the fail-safe input module.
Discrepancy time
Configured time for the -> discrepancy analysis. If the discrepancy time is set too high, the
times for fault detection and -> fault reaction are extended unnecessarily. If the discrepancy
time is set too low, availability is decreased unnecessarily since a discrepancy error is
detected when, in reality, no error exists.
DP master
A master that behaves in accordance with IEC 61784-1:2002 Ed1 CP 3/1 is known as a DP
master.
DP slave
A DP slave is a slave operated on PROFIBUS with the PROFIBUS DP protocol that behaves
in accordance with IEC 61784-1:2002 Ed1 CP 3/1.
F monitoring time
-> PROFIsafe monitoring time
ET 200S Distributed I/O System - Fail-Safe Modules
Installation and Operating Manual, 08/2008, A5E00103686-07
Glossary
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