What is the best way to backup some bytes whitout RTC backup registers in order to enter in shutdown mode.

Hello, I use STM32L476 for very low power project. I also use an external RTC because it is temperature-compensated. My question is : What is the best way to backup some bytes whitout RTC backup registers in order to enter in shutdown mode.

I had the idea to use internal flash memory but I need to backup some dozen of bytes. I need to do the same task about ten times before read all of these bytes and delete them. Because of erasing before writing, I consider that flash isn't the best way.

If anyone can help me, I'll be awsome.

Thanks in advance

Chabot Axel