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

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