The LFRC frequency is affected by temperature variation. LFRC can be calibrated to improve accuracy by using HFCLK as a reference oscillator during calibration.
The calibration must use the following sequence.
- Start the LFCLK by triggering the LFCLKSTART task.
- Start the HFCLK crystal oscillator HFXO by triggering the XOSTART task.
- Wait for the LFCLKSTARTED and the HFXO XOTUNED events.
- Trigger the CAL task to start the calibration process. The device automatically performs the calibration, adjusting the LFCLK frequency using HFCLK as reference. The DONE event is generated when calibration finishes.
- Stop HFXO with the XOSTOP task.
- Stop LFCLK with the LFCLKSTOP task.
LFCLK uses the calibrated value until the next calibration.