Method for input output expansion in an embedded system utilizing controlled transitions of first and second signals

摘要

A method for expanding input/output in an embedded system is described in which no additional strobes or enable lines are necessary from the host controller. By controlling the transitions of the signal levels in a specific way when controlling two existing data or select lines, an expansion input and/or output device can generate a strobe and/or enable signal internally. This internal strobe and/or enable signal is then used to store output data or enable input data. The host controller typically utilizes software or firmware to control the data transitions, but no additional wires are needed, and no changes are needed to existing peripheral devices. Thus, an existing system can be expanded when there are no additional control lines available and no unused states in existing signals.