Datasheet

SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
580
29.5.5 Switching Main Clock between the Main RC Oscillator and Fast Crystal Oscillator
Both sources must be enabled during the switchover operation. Only after completion can the unused oscillator be
disabled. If switching to fast crystal oscillator, the clock presence must first be checked according to what is
described in Section 29.5.6 ”Software Sequence to Detect the Presence of Fast Crystal” because the source may
not be reliable (crystal failure or bypass on a non-existent clock).