A method of operating a controller for a switch mode power converter and having connection pins, the method comprising a mode-setting phase and an operational phase and characterised in that it comprises: in the mode-setting phase: (i) polling both (a) each of a first predetermined group (176, 173) of the connection pins to sense at least one of the presence and the magnitude of a respective relatively high impedance connected between the respective connection pin and a predetermined electrical potential, and (b) each of a second predetermined group (174, 175, 177) of the connection pins to sense at least one of the presence and the magnitude of a respective further impedance connected between the respective connection pin and a respective further electrical potential, and (ii) selecting an operational mode from a plurality of possible operational modes, in response to the presence and/or magnitude of the respective one or more relatively high impedances and the respective further impedances; and in the operational phase: operating in the selected operational mode, comprising (a) providing a respective drive signal having a relatively low output impedance from each of the first group of connection pins; and (b) measuring a sense voltage on each of the second group of connection pins. in the mode-setting phase: (i) polling both (a) each of a first predetermined group (176, 173) of the connection pins to sense at least one of the presence and the magnitude of a respective relatively high impedance connected between the respective connection pin and a predetermined electrical potential, and (b) each of a second predetermined group (174, 175, 177) of the connection pins to sense at least one of the presence and the magnitude of a respective further impedance connected between the respective connection pin and a respective further electrical potential, and (ii) selecting an operational mode from a plurality of possible operational modes, in response to the presence and/or magnitude of the respective one or more relatively high impedances and the respective further impedances; (i) polling both (a) each of a first predetermined group (176, 173) of the connection pins to sense at least one of the presence and the magnitude of a respective relatively high impedance connected between the respective connection pin and a predetermined electrical potential, and (b) each of a second predetermined group (174, 175, 177) of the connection pins to sense at least one of the presence and the magnitude of a respective further impedance connected between the respective connection pin and a respective further electrical potential, and (ii) selecting an operational mode from a plurality of possible operational modes, in response to the presence and/or magnitude of the respective one or more relatively high impedances and the respective further impedances; and in the operational phase: operating in the selected operational mode, comprising (a) providing a respective drive signal having a relatively low output impedance from each of the first group of connection pins; and (b) measuring a sense voltage on each of the second group of connection pins. operating in the selected operational mode, comprising (a) providing a respective drive signal having a relatively low output impedance from each of the first group of connection pins; and (b) measuring a sense voltage on each of the second group of connection pins. (a) providing a respective drive signal having a relatively low output impedance from each of the first group of connection pins; and (b) measuring a sense voltage on each of the second group of connection pins.