What are the two communication methods in HART protocol?

HART communication methods: Point-to-Point (analog mode) - one device per wire pair, 4-20 mA analog signal carries primary variable for control, HART digital signal carries configuration and additional variables simultaneously, most common implementation. Multi-drop mode - up to 15 devices on single wire pair, all devices fixed at 4 mA (no analog signal), all communication is digital with polling, slower update rate but useful for monitoring applications (tank gauging, non-critical measurements). Point-to-point is preferred for control applications due to faster update rate and maintained analog signal for fail-safe operation.