11.8.4 PPG period when ATPSEL = 2'b1x
When comparator 2 outputs low and ATPSEL is 2'b1x, ATPHR/ATPLR (the period register in auto
period mode) is increased by USTEP and it is applied to the next cycle.
NOTE: ATPEN should be set to '1' before writing a value in a period register (ATPHR, ATPLR). Otherwise the cycle
starts with the increased period value by USTEP.