Siemens SITOP UPS1600 under STEP 7 V12 Getting Started page 26

Parameterizing the SITOP UPS1600
6.1 Buffering an S7 IO controller, including the I/O when the power fails
4. Click on the symbols to open the "Device configuration" and select "Base Unit".
5. Check that the checkbox "Buffering allowed" is selected. Select it if it is deactivated.
Note
If the checkbox "Buffering allowed" is not selected, independent of the following entries,
there is no buffering.
6. For "Connection threshold", enter the voltage value, which, when it is fallen below the
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UPS, starts to buffer.
SITOP UPS1600 under STEP 7 V12
Getting Started,