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Participant haibingma
Participant
7,769 Views
Registered: ‎09-05-2012

RTC retrieved date/time is not valid

For the RTC on my ZC702 board, I got:

 

rtc-pcf8563 5-0051: low voltage detected, date/time is not reliable.
rtc-pcf8563 5-0051: retrieved date/time is not valid.

 

What does that mean? Change battery? Or something else I need to do?

 

Thanks.

 

Haibing

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5 Replies
Xilinx Employee
Xilinx Employee
7,753 Views
Registered: ‎09-10-2008

Re: RTC retrieved date/time is not valid

I've seen that before also, I'm asking the board team what they think.
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Participant haibingma
Participant
7,732 Views
Registered: ‎09-05-2012

Re: RTC retrieved date/time is not valid

Thanks a lot, John. Really appreciate your help.

 

Just let you know that I got "low voltage dected", and I got this message for both of my boards. In theory, it shouldn't run out of battery.

 

Haibing

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Xilinx Employee
Xilinx Employee
7,706 Views
Registered: ‎09-10-2008

Re: RTC retrieved date/time is not valid

When I ask the board team it sounds like there could be some bad batteries but they are soldered on so it's a pain to change.
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Visitor dainis
Visitor
7,679 Views
Registered: ‎10-24-2012

Re: RTC retrieved date/time is not valid

For RTC is used secondary battery B2 which is not mounted on PCB.

Don't use standart Lithium coins, because this B2 battey has charging circuit!!!

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5,309 Views
Registered: ‎12-28-2014

Re: RTC retrieved date/time is not valid

For others who find this thread:

 

This warning message occurs when the VL flag in the RTC's SECONDS register is set. This flag gets set when VDD falls below a certain threshold (like low battery). It stays set until cleared by writing a zero to bit 7 of the SECONDS register (offset 0x02).

 

After updating the date and time I no longer receive this warning and the date holds through power off.

Process:

  • Stop the clock
  • Update date and time (clearing VL flag)
  • Restart clock

The RTC chip has an auto incrementing address, so you can write all date and time fields in one go.

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