Siemens SIMATIC S7-1500 Function Manual page 94

Space requirements for storing trace recordings
The "Save measurements on device (memory card)" function in STEP 7 saves Trace
recordings on your SIMATIC memory card.
Response when number reached
The "Deactivate recording" parameter repeats the measurements until the configured
"Number of measurements" is reached.
The "Overwrite oldest recording" parameter replaces the oldest measurement with the latest
measurement when the configured "Number of measurements" is reached. Please note,
however, that continuously writing data to the SIMATIC memory card shortens its service
life.
Figure 3-50 Dialog of the settings for saving measurements to the memory card in STEP 7
Number of measurements
The CPU supports a maximum of 999 measurements. While the CPU writes the trace
recordings to the load memory of the memory card, it pauses monitoring of the trigger
conditions for the trace job. After the CPU has terminated the storing of Trace recordings,
the CPU continues checking of the trigger conditions.
NOTICE
Memory required on the SIMATIC memory card
When the trace function "Measurements on device (memory card)" requires more memory
than is available on the SIMATIC memory card, undesired effects may result. Ensure there
is always sufficient free storage space to use the "Measurements on device (memory card)"
function.
In addition to the "Measurements on device (memory card)" Trace function, other functions,
such as storing data logs, use memory space on the SIMATIC memory card. Make sure
that enough memory space is available for all functions that occupy memory.
You can view the current values on the currently used space in the load memory in the
"Memory" tab on the "Diagnostics" web page.
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