42.6.5 ADC Result FIFO
The ADC has a 16-sample deep FIFO. To capture ADCn results in this FIFO, first enable the FIFO: PFFCTRL.PFFEN = 1. Then enable the FIFO for ADCn: PFFCTRL.PFFCRn= 1. FIFO results are available in the PFFDATA register.
The status of the FIFO is reflected in the CTLINTFLAG register. Setting the corresponding bits in the CTLINTENSET register enables these bits to fire the ADC Global Interrupt.