RPM for ICE, hardware and settings

Currently with a Pixhawk I have the rpm signal coming into AUX5. With plane3.7 there is a separate RPM input setting under ICE_RPM_CHAN. How do both RPM_TYPE and ICE_RPM_CHAN work together or are they separate?

What should the hardware inputs be for ICE_RPM_CHAN be and what should RPM_TYPE be set to?

Thanks RYan