• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 78 subscribers
  • Views 789 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430F6779: RTC_C module oscillator failure

BasePointer
Expert 1570 points
Other Parts Discussed in Thread: MSP430F6779

Hi,

I try to understand MSP430F6779 mcu and its modules.

I have 32867 Hz external crystal connected to XT1. 

MCLK is fed by DCO stabilized by FLL based XT1.

And LCD clock source is ACLK which is from XT1.

And RTC_C module is fed by external XT1.

I wanted to see what is going on if XT1 fails. I stop it intensionally by touching.

Result:

1. MCLK continued as is, FLL source automatically switched to REFO which is less accurate internal 32Khz source, but it is very nice and acceptable.

2. LCD, it automatically continued working with REFO. I didn't feel anything, no flicker, nothing. Nice.

3. RTC_C, it stopped counting. It just fired RTCOFIFG (failure of the 32kHz crystal oscillator) and didn't continue.

I was expecting that RTC_C will continue counting automatically through REFO in case of external crystal fails. Isn't this the case? Is there a way to tell RTC_C module that continue counting by using REFO?

Thanks.

  • 0
    Guru 227245 points

    Look at the users guide, RTC-C, first chapter.

    The RTC-C is directly sourced by the crystal, not by the clock module. So there is no fallback. In LPM3.5, the clock module is off (and no REFO, no fallback logic, nothing). To keep the RTC running, it is directly souced by the crystal, which is also powered by the backup module (if any)

**Attention** This is a public forum