Is it possible to periodically wake up while you're in VBAT mode with STM32 devices that support it? I want to be able to wake up every so often (say, every 5 minutes) and log the time in the backup SRAM that is provided. The problem is, I can't seem to find anything in the STM32L5 datasheets and application notes that indicate whether or not you can execute instructions while in VBAT mode. I also can't find anything that indicates if you can interrupt while in VBAT mode.
Also, is it possible to interrupt and save information at the very moment that power is lost and then enter VBAT mode? Or does it immediately enter VBAT mode and the hope is that I already had the information saved prior to power loss?
A third question I have, is it possible to configure the RTC to send out a signal every 5 minutes while in VBAT mode (in case I decide to have external circuitry handle things)?
The microcontroller that I am working with is the STM32L552ZE. This is a link to the datasheet: https://www.st.com/resource/en/reference_manual/rm0438-stm32l552xx-and-stm32l562xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf
For those who find themselves wondering this same thing, here is what I found based on Justme's answer:
When the microcontroller is supplied from VBAT, neither external interrupts nor RTC alarm/events exit the microcontroller from the VBAT operation (3.9.7).
I still feel that STM is being a little bit cryptic about what VBAT mode does to the microcontroller, but otherwise, it seems that you cannot execute instructions of any sort while in VBAT mode and the VBAT supply has no physical way of supplying power to the microcontroller.