How to recover calendar data after a reset

[Tony.X]

Dear Nordic Developer Zone,

I have implemented a real-time-clock using application timer which is based on the on-chip real-time counter on NRF51822.

A concern of mine is that after a reset due to a unpredictable error( i.e. stack error), is there a way to recover the previous time information?

Thanks, Tony

[Asbjørn]

As @scytulip says, you would have to write the value of the clock/time to flash periodically. This would save it during a reset. RAM will be lost if a reset occurs.

[Clem Taylor]

Are the RAMs really zeroed on reset or is it just an issue that the behavior is undefined? If the ram doesn't really have a global reset you might be able to stick the current time and a crc in ram someplace and at least have a chance at recovering the current time. I've done this with DRAM (filled one page with the data we wanted to keep and a 64bit CRC, repeated over and over) the data could often survive for 10s of seconds with a complete power loss. DRAM != SRAM, but it might be something to try.