An apparatus includes a digital interface circuit configured to provide a digital interface. The digital interface is configurable based on a mode of operation of the digital interface circuit. The apparatus also includes input and output level-shift circuits. The input level-shift circuit is configured to shift a voltage level of an input signal for the digital interface circuit. The output level-shift circuit is configured to shift a voltage level of an output signal from the digital interface circuit. The input level-shifting and the output level-shifting are based on first and second level-shift input voltages. The apparatus further includes a mode detector configured to identify at least two modes of operation for the digital interface circuit based on the first and second level-shift input voltages. For example, the digital interface circuit could be configured to function as a serial or parallel interface depending on which level-shift input voltage is greater.