12.4.2.1 Internal High Frequency Oscillator (OSCHF) Operation

The OSCHF is an internal oscillator generating a frequency up to 24 MHz. The OSCHF frequency is selected by writing to the Frequency Select bit field in the OSCHFCTRL register (OSCHFCTRL.FRQSEL). The OSCHF is by default enabled and can only be disabled if the On-Demand Operation bit in the OSCHF Control register (OSCHFCTRL.ONDEMAND) is set and no peripheral is requesting the OSCHF clock.

The OSCHF clock is output as soon as the oscillator is ready (STATUS.OSCHFRDY = 1). After reset, OSCHF serves as the default clock source at 4 MHz. The OSCHF can take as input an external 32.768 kHz oscillator to tune against to reduce drift.