The present disclosure is directed to an electromechanical surgical system having an end effector and an adapter assembly for selectively interconnecting the end effector and a hand-held surgical instrument. A one-wire bidirectional serial communications interface or bus extends through the end effector, the adapter assembly, and the hand-held surgical instrument. The hand-held surgical instrument includes a master circuit coupled to the bus and configured to identify or control the adapter assembly or the end effector. A power source is couplable to the bus and configured to provide power to the adapter assembly or the end effector. A first switch connects the master circuit to the bus and a second switch connects the power source to the bus. A processor controls operation of the hand-held surgical instrument. The controller has a wake-up pin connected to the bus and is configured to receive a presence pulse from the adapter or end effector.
