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TM4C1294NCZAD: TM4C1294 internal RTC (real time clock) module accuracy?

cheng gu
Prodigy 90 points
Part Number: TM4C1294NCZAD

Tool/software:

Hi Team,

 what is the TM4C1294 internal RTC (real time clock) module accuracy? I can't find the accuracy data of the RTC in the micro's datasheet. thanks.

Best
Gu

  • 0
    TI__Guru**** 191886 points

    Hi Gu,

      The RTCCLK can take the clock source among three different clock sources: See below. If you choose either the 32.768kHz OSC or the external 32.768kHz clock source (a direct square wave clock) then the RTC accuracy depends on your external crystal or the oscillator. You will need to find out the clock tolerance from your crystal/oscillator datasheet.  

    If you choose the internal low frequency oscillator (LFIOSC) then the tolerance is high. The 

  • 0 in reply to Charles Tsai
    Prodigy 90 points

    Hi Charles,

     thanks for your quick response, if I am using a typical ±20ppm 32.768KHz crystal with the TM4C1294 RTC, does it mean my error is 1 second per 13 hour?

    equation is (1000000/(60*60*20)). is there any other factor need to be count into this error calculation equation? do you have any error rate test sample data of the RTC using external 32.768Khz crystal? 

    Best
    Gu

  • 0 in reply to cheng gu
    TI__Guru**** 191886 points

    cheng gu said:

    if I am using a typical ±20ppm 32.768KHz crystal with the TM4C1294 RTC, does it mean my error is 1 second per 13 hour?

    equation is (1000000/(60*60*20)).

    I agree with your calculation. 

    cheng gu said:
    is there any other factor need to be count into this error calculation equation?

    The accuracy of your external crystal can be affected by things like temperature changes load fluctuations, and even aging but I think they should be taken into account by the ppm that is specified in your crystal datasheet. 

    cheng gu said:
    do you have any error rate test sample data of the RTC using external 32.768Khz crystal? 

    No, we don't have this data.