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.

主权项

1. A computing system comprising:
a computing device configured to transmit data to a peripheral device and an expansion device; and one or more data lines coupling the computing device to both the peripheral device and the expansion device; wherein the peripheral device is configured to read data from at least one of the one or more data lines in response to receiving an intermittent pulse; wherein the expansion device is configured to read data on the one or more data lines during an interval between intermittent pulses in order to detect a particular transition in the data on the one or more data lines, wherein the computing device is configured to exclude the particular transition if the data is intended for reading by the peripheral device.