With 256 capcodes and 7 VCO cores, there are altogether 1792 combinations. For a particular frequency, it may be difficult to manually select the right VCO core and capcode, if not impossible. A VCO calibration algorithm is embedded in the chip so that the selection of capcode and VCO core is transparent to the users. In addition to frequency selection, the calibration algorithm also optimizes the phase noise by adjusting the bias of the selected VCO (register R16, VCO_DACISET).