ADC32RF45: how to reset NCO

No, there is no single reset function to reset the programmable NCO words. You'll have to write all words with the desired value.

NCO accumulator can be reset on every SYSREF rising edge, in the event where NCO must be aligned across devices on a common SYSREF edge, however that doesn't sound like what you are wanting. Best option is to re-write the NCO word register fields manually.

Thanks