Apparatus and method for supplying power and wake-up signal using host port's signal lines of opposite polarities

摘要

An apparatus and a method for using a host port to provide power to a level converter for voltage level conversion between a CMOS based palm-top computer and RS-232 host processor are disclosed. Energy from the host RS-232 port is extracted by the level converter from the request-to-send line (-12 V) and the data-terminal-ready line (+12 V). The host port request-to-send line may also be used to send a wake-up signal to turn on the palm-top computer. A momentary (1 millisecond) transition in the request-to-send line of the host port causes the level converter to present an appropriate signal on the wake-up pin of the palm-top computer.