Vism. XVII, 298 classifies the twelve factors into three rounds(vaṭṭa):
the round of defilements (kilesa-vaṭṭa)
the round of kamma(kamma-vaṭṭa)
and the round of results(vipāka-vaṭṭa)
xvii 298. 4. With triple round it spins forever (§288): here formations and becoming
are the round of kamma. Ignorance, craving and clinging are the round of
defilements. Consciousness, mentality-materiality, the sixfold base, contact and
feeling are the round of result. So this Wheel of Becoming, having a triple round
with these three rounds, should be understood to spin, revolving again and
again, forever, for the conditions are not cut off as long as the round of defilements
is not cut off.