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MSP 430F5418 RTC calibration

TJ12723
Prodigy 50 points

I try to integrate the RTC calibration feature. But it seems that any changes in the RTCCAL register don't affect the RTC signal on the RTCCLK output signal. In the user guide I found the notice that only the 1Hz-signal is affected by the calibration settings but I cannot measure any frequency changes at all. Has anybody similar problems?

  • 0
    Guru 58965 points

    (1) Can you measure the RTCCLK down to a few ppm?

    (2) Are you using a watch crystal that is stable within a few ppm?

    (3) Did you set RTCMODE=1 and RTCCALF=11?

    (4) Are you aware of RTC bugs in the silicon you are using?

  • 0 in reply to old_cow_yellow
    Prodigy 50 points

    Thanks for your reply.

    I can measure a deviation from 7 ppm. But there is no changing of the deviation if I modify the RTCCAL register. Can you measure a variation if you modify the register?

     

     

  • 0 in reply to TJ12723
    Prodigy 30 points

    I see that RTCCAL5 and RTCCAL4 do correctly cause discrete freq steps approximately every 30 secs. I can change the step direction with RTCCALS. However I cannot get any effect with the four lower bits RTCCAL3 - RTCCAL0. I see the correct bits set in memory at 0x04A2. It appears to me to be a problem in the processor.

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