该文件是“通讯系统”的电路图实例，本电路图注重于USB2.0、RS232、以太网的连接方法以及外围电路设计，为读者朋友提供一个完整的电路实例。而C6713电路部分，只涉及C6713与三个器件的连接关系，至于C6713的其他部分（如SDRAM、FLASH等）都略去,读者可参考另外相关的章节。-The document is " communication system"　circuit instance, the diagram focuses on USB2.0, RS232, Ethernet connection method and the external circuit design, the reader will provide an example of a complete circuit. The C6713 circuit part, only involves the C6713 and the connection of the three devices, as in other parts of C6713 (such as SDRAM, FLASH, etc.) are omitted, the reader may refer to other relevant chapters.