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Original question:

MSP430F6779A: About UCS Module Fail-Safe Operation

MSP430F6779A: What happens when using the RTC_C module during the crystals is unstable?

TinK
Intellectual 795 points
Part Number: MSP430F6779A

Because our device needs approximately 600 ms to wait for a stable 32768 Hz crystal.



What happens when using the RTC_C module during the crystals is unstable?


Will fail-safe operation of the UCS module switch the RTC module to be operated by the internal clock REFO?

If there is no fail-safe operation for the RTC_C module, is there a serious error such as the MCU freezing or crashing?

  • 0
    TI__Mastermind 39045 points

    Hi,

    TinK said:
    Will fail-safe operation of the UCS module switch the RTC module to be operated by the internal clock REFO?

    Based on the description in UG chapter 5.2.12 UCS Module Fail-Safe Operation. Only if the crystal oscillator fault bits XT1LFOFFG is set, the UCS will switch the reference clock source. 

    So, if the crystal is on unstable but not trigger a fault flag, the RC module can still run with this unstable clock source. It would not cause MCU freezing or crashing because it has a fail-safe operation.

    In this example code, the code waits for the LFXT to stable and then configure the UCS configuration. 

    https://dev.ti.com/tirex/explore/node?node=A__AA3dUu64Y5GEFwism6plaA__msp430ware__IOGqZri__LATEST

    Best regards,

    Cash Hao

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