Siemens SIMATIC ET 200AL System Manual page 1436

Principle of operation
The CPU enters the first three events of an event type in the diagnostics buffer. It then
ignores all subsequent diagnostics of this group.
At the end of the monitoring time (interval), the CPU generates a group alarm in which it
enters the diagnostics and the frequency of this diagnostics during the elapsed interval. If
these diagnostics also occur in the intervals that follow, the CPU only generates one group
alarm per subsequent interval.
A diagnostic surge leaves the following pattern in the diagnostics buffer: Three individual
messages followed by a series of group alarms. This series can consist of two, three or more
group alarms depending on the selected monitoring time and duration of the diagnostic
surge.
①
②
③
④
Figure 9-57
Communication
Function Manual, 05/2021, A5E03735815-AJ
Diagnostic results of a group (of a type), for example "Sampling rate could not be reached".
Interval (monitoring time): When a diagnostic event occurs the first time (or reoccurs), the
monitoring time is started (or restarted).
Single alarms: The first three diagnostic events from the same group are entered in the diag-
nostics buffer immediately. Starting with the fourth diagnostic event, the CPU generates only
group alarms. If a diagnostic event of this group occurs after a pause of at least one interval, the
CPU enters a single alarm in the diagnostics buffer and restarts the monitoring time.
Group alarms: After three diagnostic events, the CPU only generates a group alarm as a sum-
mary of all additional diagnostic events in this interval. If these diagnostic events also occur in
the intervals that follow, the CPU only generates one group alarm per subsequent interval.
Summary of diagnostics
OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
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