An interface module for use in a power conversion system includes a first current circuit coupled to a single external programming terminal to conduct a programming current through an external programming circuitry coupled to the single external programming terminal. A current comparator is coupled to the first current circuit to compare a current representative of the programming current with an internal current. A mode select circuit is coupled to the current comparator to generate a select signal to select one of a plurality of modes in response to a comparison of the current representative of the programming current with the internal current by the current comparator. A second current circuit is coupled to the first current circuit and the mode select circuit to generate a reference current in response to the programming current and the select signal from the mode select circuit.