A microcontroller includes an input pin and internal pull-up and pull-down circuits. External pull-up and pull-down circuits are also coupled to the input pin. The microcontroller is operable according to different configuration modes which include configuring the input pin in a floating state. A control logic then configures the internal pull-up and pull-down circuits according to an internal pull-up mode to acquire a first input voltage signal (at a first logic value) from the input pin, and further configure the internal pull-up and pull-down circuits according to an internal pull-down mode to acquire a second input voltage signal (at a second logic value) from the input pin. A selection of the operating mode of the MCU is then made based on the acquired first and second logic values.