Online and diagnostic tools
15.15 Tracing and recording CPU data on trigger conditions
S7-1200 Programmable controller
1348 System Manual, V4.2, 09/2016, A5E02486680-AK
Saving trace measurements to the memory card
The S7-1200 CPU can only save trace measurements to the SIMATIC memory card. If you
do not have a memory card in your CPU, the CPU will log a diagnostic buffer entry if the
program attempts to save trace measurements with no SIMATIC memory card present in the
CPU. The CPU limits the space allocated to trace measurements such that 1 MB of external
load memory must always be available. If a trace measument would require more memory
than the maximum allowance, the CPU will not save the measurement and will log a
diagnostic buffer entry.
In addition, if you select "Overwrite oldest recording" in STEP 7, the continual writing can
reduce the lifetime of load memory. When you select "Overwrite oldest recording", the CPU
replaces the oldest measurement with the newest measurement after it has stored the
configured number of trace measurements, and continues tracing and saving
measurements. Overwriting the oldest measurements is useful in capturing intermittent
problems.
The CPU supports a maximum of 999 trace measurement results. During the time that the
CPU is saving the trace measurements to load memory, the CPU does not check the trigger
condition for the trace job. Once the CPU finishes saving the trace measurements, the CPU
resumes checking for trigger conditions.
See the STEP 7 information system for details about how to program a trace, how to
download the configuration, upload the trace data, and display the data in the logic analyzer.
You can find detailed examples there in the "Using online and diagnostics functions > Using
the trace and logic analyzer function" chapter.
In addition, the online manual "Industry Automation SINAMICS/SIMATIC Using the trace and
logic analyzer function" (https://support.industry.siemens.com/cs/ww/en/view/64897128) is
an excellent reference.
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