Siemens SIMATIC ET 200AL, System Manual

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Glossary
Distributed I/O system
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System Manual, 08/2021, A5E31861578-AJ
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 adequate carrier → actuator will not respond to this and will
remain activated.
Device
Device that can send, receive or amplify data via the bus, e.g. IO device via PROFINET IO.
Diagnostics
Monitoring functions for the detection, localization, classification, display, and further
evaluation of errors, faults, and alarms. They run automatically while the system is in
operation. This increases the availability of systems by reducing commissioning times and
downtimes.
Discrepancy analysis
The discrepancy analysis for equivalence/non-equivalence is used for fail-safe applications to
prevent errors from time differences between two signals for the same function. The
discrepancy analysis is initiated when different levels are detected in two associated input
signals (when testing for non-equivalence: the same levels). A check is performed to
determine whether the difference (for nonequivalence testing: the same levels) has
disappeared after an assignable time period, the so-called 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
Configurable time for the → discrepancy analysis. If the discrepancy time is set too high, the
fault detection time and → fault reaction time 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.
Distributed I/O system
System with input and output modules that are configured on a distributed basis, far away
from the CPU controlling them.
eCoding plug connector
The eCoding plug connector stores the external addresses of F-source and F-destination of
the I/O module. The eCoding plug connector simplifies module replacement.