RTC not retaining date and time after power cycle

Discussion around product based on ARM Cortex M3 core.
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elphnei
Posts: 3
Joined: Fri Jul 17, 2015 12:36 pm

RTC not retaining date and time after power cycle

Wed Jul 27, 2016 4:57 pm

I am using an SAM3U4E device and can successfully program and read back from the RTC whilst power is connected. However, when power is removed from my board, the RTC date and time have reset back to the 'factory default'. I have VDDBU connected to a battery and can measure it's value directly at the device pin (139).

I was expecting the RTC information to be kept current with the VDDBU being present when main power is removed. Am I missing some setup condition? I've studied the user guides and example code and can't see anything that I may be missing.

Thanks for any feedback.

N.
elphnei
Posts: 3
Joined: Fri Jul 17, 2015 12:36 pm

Re: RTC not retaining date and time after power cycle

Tue Aug 02, 2016 10:35 am

Found the problem. NRSTB needs to be floating. I have it hooked up as a watchdog reset - which works fine, as long as you don't want to retain RTC time!

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