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TM4C1231H6PZ: LFOSC value out of Tiva

Alberto Soattin
Genius 16905 points
Part Number: TM4C1231H6PZ

Hi Support,

I would need your help regarding RTC time trimming.

Is a possibility to output LFOSC clock 32768Hz on a pin to measure frequency accurate?  (Measurement directly on XTAL OSC pins  would influenced frequency).

Can you provide an equation for calculation of value for trim register based on measurement of frequency?

Thanks and regards,

Alberto

  • 0
    Guru 117855 points

    Applaud your recognition that, "probing XTAL OSC pins (often) will "pull" Fxtal."        Indeed - that's to be avoided.

    Firm/I do not work w/your MCU - yet if the "LFOSC" routes to the MCU's Timers (which is suspected to be true - yet you must check) cannot you configure a Timer into PWM Mode?

    In that mode - a (proper) low impedance, Timer output signal (frequency replica) of "LFOSC" is generated - which enables a "non-compromised" frequency measurement...

  • 0 in reply to cb1_mobile
    TI__Guru**** 184446 points
    Thanks, cb1!

    Alberto,
    I will use cb1's suggestion but take the LFIOSC as a dedicated clock source for the PWM module (not Timer in PWM mode). This way the LFIOSC will not be used the clock source for SYSCLK.