嵌入式下载模块，包括，tftp协议栈，Xmodem传输，以及文件的crc校验-Embedded system for download modules, including, tftp protocol stack, Xmodem transmission, as well as the checksum crc file

NOTES: * String table and symbols are not read in. The application must explicitly * request load of string and symbol tables.-NOTES:* String table and symbols are not read in. The application must explicitly* request load of string and symbol ta