Prior to bypassing the Main crystal oscillator, the external clock frequency provided on the XIN pin must be stable and within the values specified in the XIN Clock characteristics in the section “Electrical Characteristics”.
The sequence is as follows:
1. Ensure that an external clock is connected on XIN.
2. Enable the bypass by setting CKGR_MOR.MOSCXTBY.
3. Disable the Main crystal oscillator by clearing CKGR_MOR.MOSCXTEN.