220.127.116.11. User Calibration
The I/O PLL must be recalibrated for any of the following conditions after device power up:
- Dynamic I/O PLL reconfiguration that changes the M or N counter settings is performed.
- Change of the reference clock frequency to the I/O PLL.
Recalibration is not necessary when using clock switchover to a secondary reference clock with a different frequency than the primary reference clock. The I/O PLL stores the calibration settings for both reference clocks after power-up calibration.