19.5.5 Bypassing the Main Crystal Oscillator
Prior to bypassing the Main crystal oscillator (CKGR_MOR.MOSCXTBY=‘1’), an 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”. Then the Main crystal oscillator must be enabled by setting CKGR_MOR.MOSCXTEN to 1.
