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RF430FRL152H: Timer implement through HFOSC

Evan Wang
Expert 4670 points
Part Number: RF430FRL152H

Hi All,

The customer is using the internal HF oscillator of RF430FRL152H for the timer function.

For example, the counter will add one in the Reg every 5 sec.

 

After a few days of testing, they found the number of counter Reg is quite different.

By averaging the difference, almost 3 secs difference every 5 mins.

The above testing is based on 3 pcs of the RF430FRL152H.

  • ( 4045 – 4024 ) * 5 mins = 105 mins
  • 1 / 105 mins * 5 mins * 60 secs = Almost 3 secs difference in every 5 mins.

According to the spec, it seems that the freq has +/- 20% difference.

And I believe it will affect this time error.

 

 

May I know how to judge this time difference?

And usually, we use ppm data for crystal spec so I’m not sure how to judge it.

FW coding is the same for those 3 pcs devices.

 

Looking forward to your feedback.

Thank you.

  • 0
    TI__Genius 12995 points

    Hello Chia Cheng,

    of cause the error of the timer interval is scaling with the accuracy of the used clock. In this example it would require 1140000000 HFOSC clock cycles to generate the 5 min time interval at 3.8 MHz. If the oscillator would operate at the minimum specified frequency of 3.04 MHz then the timer interval would last 6 min and 15 seconds with the same number of clocks (1140000000). So the 2.2 seconds error per 5 min interval in the customers experiment is actually a good result.

    The HFOSC of the RF430FRL152H is not comparable to a crystal oscillator accuracy. If such accuracy is required, then it would be necessary to connect an external crystal oscillator to the RF430FRL152H.

    Best regards,

    Andreas.

  • +1
    TI__Genius 12995 points

    Hello Chia Cheng,

    as you indicated via e-mail, this was the information, you were looking for. So I will close this thread now. You can still reply to this thread or create a new one if you have further questions.

    Best regards,

    Andreas.