The MCU type is MC56F84763, if environment temperature is higher than 70 degree Celsius, one of the prototype external crystal stop working, there is no waveform output of XTAL and EXTAL pin. If replace the crystal with another one and this crystal is proved to be good, the issue still exists. It seems like not crystal issue. My question is if MCU detects external crystal output abnormal or PLL loss of lock failure, whether OSC module will automatically shut down XTAL and EXTAL voltage, make the external crystal stop oscillating?
There is no automatic action.
It is up to the firmware to detect this and switch over to the internal relaxation osc.
Get it. Thanks a lot!