Siemens SIMATIC ET 200AL, System Manual

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Setting and determining system diagnostics
4.2 Options for displaying system diagnostics
Diagnostics
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Function Manual, 11/2019, A5E03735838-AF
4.2.2.6 CPU diagnostics buffer
Definition
Each CPU and some other modules have their own diagnostics buffer, in which detailed
information on all diagnostic events is entered in the order in which they occurred.
The CPU diagnostics buffer can be displayed on all display media (STEP 7, SIMATIC HMI
devices, SIMATIC S7-1500 Web server and display of the CPU).
Diagnostic events
The entries available in the diagnostics buffer include:
● Internal and external errors on a module
● System errors in the CPU
● Operating mode transitions (e.g., from RUN to STOP)
● Errors in the user program
● Removal/insertion of modules
● Security events
The contents of the diagnostics buffer are stored in the retentive memory in case of a
memory reset of the CPU. Errors or events can be evaluated even after a longer period of
time thanks to the diagnostics buffer to determine the cause of a STOP or to trace the
occurrence of a single diagnostic event and to be able to assign it.