这是ARM对AVR/C51升级的源程序xmodem，先通过TFTP将升级文件从PC下载到ARM，然后按照自己的握手方式，通过xmodem升级到AVR，已在产品中使用。-This is the source ARM upgrade of AVR/C51 xmodem, the first upgrade by TFTP to download files from PC to ARM, and then shook hands with their own way through xmodem upgrade to the AVR, has been used in the product.