RTC backup registers after power off and on

[sanctified]

Hi ST Community,

I am using the RTC on the STM32l100RBT6 µC to display the date and time every hour. It is battery powered and therefore at some point i would have to change the batteries, therefore, the µC will lose power.

I have thought of using the RTC Backup registers to store the last date and time but according to the datasheet, the backup registers will be reset if there is a loss of power or am i wrong? and also the RTC clock will be stopped anyway.

My question is, is there a way to make sure that after power up the RTC is not initialized again because then the displayed date and time will be wrong? and also make sure that the date and time will still be correct after power up?

P.S. : the µC has no VBAT pin for connecting the RTC Clock and Backup registers to.

[Peter BENSCH · Accepted solution]

Your P.S. is exactly the reason why the backup registers and the RTC data can only be preserved when some VDD is present.

It looks like the only solution to your issue is to change to a device with VBAT pin.

Does it answer your question?

/Peter

[sanctified]

Okay :(

yes it answers my question. thank you 🙂