METHODS AND APPARATUS FOR FULL I/O FUNCTIONALITY AND BLOCKING OF BACKDRIVE CURRENT

摘要

An input/output (I/O) port designed for electrical interconnection with multiple similar ports includes an input read circuit, an output drive circuit, and a circuit to control the port for input or output mode by electrically disconnecting the output drive circuit from the port. Also included is a back drive current protection circuit placed in series in between an external (I/O) line and the input read and output drive circuits which blocks backdrive currents from other active processors when the processor that includes the protection circuit is in a powered down state while still allowing full input/output functionally in a powered up state.