17.6.4 32 kHz Internal Oscillator (OSC32K) Operation

The OSC32K provides a tunable, low-speed and low-power clock source.

The OSC32K can be used as a source for the generic clock generators, as described in the GCLK – Generic Clock Controller.

The OSC32K is disabled by default. The OSC32K is enabled by writing a one to the 32 kHz Internal Oscillator Enable bit (OSC32K.ENABLE) in the 32 kHz Internal Oscillator Control register. It is disabled by writing a zero to OSC32K.ENABLE. The OSC32K has a 32.768 kHz output enabled by writing a one to the 32 kHz Internal Oscillator 32 kHz Output Enable bit (OSC32K.EN32K). Both of the OSC32K.ENABLE and OSC32K.EN32K bits must be set for the clock to start. When the clock is stable, the PCLKSR.OSC32KRDY bit will go high and the clock will propagate in the design.

The frequency of the OSC32K oscillator is controlled by the value in the 32 kHz Internal Oscillator Calibration bits (OSC32K.CALIB) in the 32 kHz Internal Oscillator Control register. The OSC32K.CALIB value must be written by the user. Flash Factory Calibration values are stored in the NVM Software Calibration Area (refer to NVM Software Calibration Area Mapping). When writing to the Calibration bits, the user must wait for the PCLKSR.OSC32KRDY bit to go high before the value is committed to the oscillator.