Fail-Safe Condition Clearing

The Fail-Safe condition is cleared after a device Reset, execution of a SLEEP instruction, or a change to the NOSC/NDIV bits. When switching to the external oscillator or PLL, the Oscillator Start-up Timer (OST) is restarted. While the OST is running, the device continues to from HFINTOSC. When the OST expires, the Fail-Safe condition is cleared after successfully switching to the external clock source.
Important: Software must clear the OSFIF bit before switching to the external oscillator. If the Fail-Safe condition still exists, the OSFIF bit will be set again by module hardware.