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MSP430FR5994: I couldn't use RTC module of MSP with external clock source.

mustafa altuntas
Prodigy 15 points
Part Number: MSP430FR5994

Hello,

In my project I used msp430fr5994. I connected a 32khz crystal oscillator to LFXIN and LFXOUT pins. I configured these pins as LFX pins. After that I use the RTC module of MSP and I had no problem.

In my project's second part I removed the crystal and I connected a 32khz external clock source to LFXIN pin. (LFXOUT is empty.) I configured LFXIN pin as LFX pin, LFXOUT pin as GPIO pin and i also set LFXBYPASS bit.

But after these changes, my project did not work, and my RTC calendar register didn't change. (sec, min, day, etc. registers)

Do i have any mistake while I using external clock source for RTC module of MSP ?

Thanks.

  • 0
    TI__Intellectual 2065 points

    Hi Mustafa,

    Take a look at section 10.1.2 in the datasheet here, is your external clock connected the same way?

  • 0 in reply to Amruta Deole
    Prodigy 15 points

    In my project's first part, yes I connected the crystal to LFXIN and LFXOUT by same way as section 10.1.2. And I was able to run RTC module successfully.

    After that I passed to my project's second part. I removed crystal and capacitors from LFXIN and LFXOUT pins. I connected external clock source (32khz square wave source not crystal!) to LFXIN. I configured LFXOUT pin as GPIO and I set the LFXBYPASS bit from the clock system register.

    After that I repeat my test like my project's first part. But I failed to run the RTC module at my tests.

    Is there anyobstacle to use external clock source to run RTC module?

    In my project's second part my clock source is not a crystal, it is a third part ic which generates 32khz square wave.

    Thanks.

  • 0 in reply to mustafa altuntas
    TI__Intellectual 2065 points

    Hi Mustafa,

    So for any unused pins--here, it would be LFXOUT--you will need to terminate them. Looking at Table 7-4 from the datasheet below, you will want to follow guidelines for Px.0 to Px.7 and make sure that the PxDIR.n is set. Hopefully, this will solve your issue if you have not already tried this. 

    Best,
    Amruta 

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