1. A serial interface apparatus comprising: a first and second input; the second input comprising a logic level signal and a non-logic level signal coupling to the input of a level shifter; and the second input also coupling to a location requiring a non-logic level signal; wherein the non-logic level signal comprises a voltage different from a logic level signal; wherein on the second input, a first part of communication comprises one or more logic level pulses, and a second part of communication comprises one or more non-logic level pulses; wherein on the second input, the non-logic level signal and the logic level signal provide different functions.