此文档描述的是USB设备中间层的通用属性与操作。这些属性与操作由设备的特定功能的部分用于通过总线接口最终与主机(host)的通信-This document describes the middle layer of USB device and operation of common attributes. These attributes and operation of the equipment part of specific functions for the adoption of the final with the host bus interface (host) communications