说明：  XMODEM 是一种适合在两个计算机之间进行文件传输的简单协议。嵌入式系统调试环境经常利用此协议或其变体，通过UART 端口进行image 的下载。实践者通过此实验环节可对通信协议的基本要素有较深入的了解，同时对通信协议在实时操作系统环境下的实现方式有初步了解。
(XMODEM is a fit between the two computers Simple File Transfer Protocol. Debugging embedded systems often use this protocol environment or its variants, through the UART port for image downloading. Practice through this experiment, could be on the basic elements of communication protocols have a better understanding of communication protocols at the same time in real-time operating system environment to achieve a preliminary understanding of the way.)