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Glossary
Channel Group
Channel Number
Channel-specific
passivation
Configuration
CRC
CRC Signature
D
Discrepancy
Analysis
11-2
The channels of a module are grouped together in a channel group.
Certain parameters in STEP 7 can only be assigned to channel groups,
rather than to individual channels.
The inputs of an I/O module are identified uniquely by means of the
channel number and the channel-specific diagnostic messages are
assigned.
In this passivation method, when a -> channel fault occurs, only the
channel involved is passivated (method available in S7 F/FH systems
only). In the event of a module fault, all channels of the -> fail-safe I/O
module are passivated.
Systematic arrangement of individual I/O modules (configuration)
Cyclic Redundancy Check
A CRC signature in the safety message frame is used to safeguard the
validity of the process values in the safety message frame, the
correctness of the assigned address references, and the safety-related
parameters.
Discrepancy analysis for equivalence or nonequivalence is used for fail-
safe inputs to determine faults based on the time characteristic of two
signals with the same functionality. Discrepancy analysis is initiated
when different levels are detected for two associated input signals (for
nonequivalence testing, when the same levels are detected). After a
programmable time interval (so-called -> discrepancy time) has elapsed,
a check is made to determine whether the difference has disappeared
(for nonequivalence testing, whether the agreement has disappeared). 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 fail-safe input module.
In the case of redundant I/O (S7 FH systems only):
•
The discrepancy analysis is performed between the two input signals
of the redundant input modules by the fail-safe driver blocks of the
S7 F Systems optional software.
ET 200eco Distributed I/O Station Fail-Safe I/O Module
A5E00297494-02
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