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MSP430F6746: There is a problem with RTC

da
Expert 2780 points
Part Number: MSP430F6746

Hi,

When MSP 430 is running on battery, rarely RTC value is read with strange value.
It is highly likely that the RTC year has reached 2099 or more from the value after occurrence.
It occurs when only RTC and WDT are operating.
(The probability of occurrence of this problem is quite low.)

Checking that READY is set in the program, RTC reading is done.

Even on the board where the problem occurred, the batteries were not running out,
RTC time merely goes wrong, there are no problems with other operations.

Q1:
Is not there any cause or countermeasure that might cause such a problem?


Q2:
Does such a problem occur when the supply voltage drops?

Regards,
Da

  • 0
    TI__Genius 10980 points
    Hi Da,

    I do not believe that there is anything that should be causing such a problem. Do you ever see this when the device is powered by USB instead of battery? Also, what is the supply voltage when you see the issue? Are there times when the supply voltage drops that low where you don't see that issue?

    Regards,
    Nathan
  • 0 in reply to Nathan Siegel
    Expert 2780 points
    Thank you for your reply.
    Because the probability of occurrence is very low, this problem can not be confirmed
    in the experimental environment.
    >
    The current algorithm includes processing to write the initialization value
    when more than 2099 years are read.
    >
    The problem of this time was found not because time elapsed from the set time,
    there were multiple individuals with time elapsed from the initialization value.
    >
    I confirmed the power supply of the individual that caused this problem,
    but since there was no problem with the voltage,
    it is unlikely that such a problem occurred due to the battery running out.
    But I doubt the power supply.
    >
    It is an additional question.
    If the RTC power supply goes down, is register 0 such as RTCYEAR readable for 0?
    It was so in the result of the experiment here.
    Regards,
    Da
  • 0 in reply to da
    TI__Genius 10980 points
    Hi Da,

    Assuming I am understanding your question correctly, as long as the power supply is still within the recommended operating conditions specified in the datasheet, all registers should still be readable. Are you saying that the RTCYEAR is showing a value of 0 when you are not expecting that?

    Regards,
    Nathan
  • 0 in reply to Nathan Siegel
    Expert 2780 points

    Hi,

    There are two kinds of questions, it is about normal condition and abnormal condition.

    *About questions on normal conditions
    As a normal condition, we can not deny the possibility that it is abnormal condition.

    *About questions about abnormal condition.
    I heard that RTC power supply is separated as a separate domain.
    Normally RTC power is backed up and RTC is maintained.
    However, I think that there is a case that RTC power is turned off,
    so I want to know the behavior in that case.

    In this experiment, when the power of the RTC module was turned off,
    register values such as RTCYEAR could be read as 0x0000.
    Is this normal behavior?

    Regards,
    Da

  • 0 in reply to da
    TI__Genius 10980 points
    Hi Da,

    Could you please explain what you mean by "RTC power is turned off"? Is power to that module no longer being supplied, or are you configuring a register value to disable the module?

    Regards,
    Nathan
  • 0 in reply to Nathan Siegel
    TI__Genius 10980 points
    Hi Da,

    Has this issue been resolved? If so, please mark it as answered. If not response soon, this thread will be closed due to inactivity.

    Regards,
    Nathan
  • 0 in reply to Nathan Siegel
    Expert 2780 points

    thank you for the advice.

    It is when the power of the RTC module is turned off.

    Regards,
    Da

  • 0 in reply to da
    TI__Genius 10980 points
    Hi Da,

    You would still be able to read the register values, as the device will still be powered on even if the RTC module is not. The value would read 0x0000 because the register value would have been reset.

    Regards,
    Nathan
  • 0 in reply to Nathan Siegel
    Expert 2780 points

    Thanks Nathan

    Is this 0x0000 equal to all RTC registers, or RTC register undefined in the document (slau208p.pdf)?

    For example, the reset value of RTCTCMP is 0x4000, is it also 0x0000?

    Regards,
    da

  • 0 in reply to da
    TI__Genius 10980 points
    Hi Da,

    Those values should read whatever default value is listed in the User's Guide. This is the value that the register will contain upon startup.

    Regards,
    Nathan

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