Abstract: Methods and data processing systems are provided to share a common pin between two circuits in microcontroller unit (MCU). Signals are received at a common pin included in the MCU. If the first circuit has been enabled, then the received signals are analyzed to determine whether the signals are valid command signals for the first circuit. If the signals are not a valid command signal, then a second circuit is performed. If the first circuit has not been enabled, then an alternate function is performed. One of the operations performed by the alternate function is to determine whether to enable the first function. In one embodiment, the first circuit is a background debug controller of the MCU and the second circuit is a reset circuit.