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Are the RTC backup registers guaranteed to be zero?

Patrick Morwald
Associate II

Hi,

when the backup power domain gets reset, are the RTC backup registers guaranteed to be zero or can they be any arbitrary value?

3 REPLIES 3
T J
Lead

Generally the whole point of a battery backed ram is to save the ram contents.

Usually there is no "Zero" hardware functionality, only a program solution you would create.

for a known stable state, use the last two bytes as a checksum of the entire backupRam-2 bytes

then you will know if your array has been cleared and initialised or else it needs clearing, and add checksum.

Patrick Morwald
Associate II

Ok thanks for the idea with the checksum. Maybe i did formulate my question not right, i meant the condition of the backup registers after there was no power at all to the whole Chip, including no backup power.

Thanks anyways!

T J
Lead

I believe the data will be randomly set on a virgin power up.