Device-dependent selection between modes for asymmetric serial protocols

摘要

A portable communication device (PCD) can automatically switch into different operating modes of an asymmetric communication protocol (such as USB) depending on the type of accessory connected. For example, the accessory can signal whether the PCD should operate in a first mode or a second mode using a hardware indicator such as identification resistor across two pins of a multi-pin connector and/or a software indicator such as a command protocol. The PCD can detect the accessory's signal and switch to the operating mode requested by the accessory.