文件名称:USB
介绍说明－－下载内容均来自于网络，请自行研究使用
usb和串口是经常用到的计算机接口，现在介绍一下他们各自的规范，以后设计时可以参考-usb and serial ports are often used in computer interface, and now tell us about their own norms, since the design can refer to
(系统自动生成,下载前可以参看下载内容)
下载文件列表
USB 通用串行总线技术规范简介 [简体中文].pdf