说明：  采用SN75LBC184来实现RS232C与RS485串行口的转换,从而使PC机具备主从式多机通讯 功能,实现对多个单片机组成数据采集终端的通讯与管理. 约定一种简单和有效的串口通讯协议,根据 这种通讯协议设计出单片机与PC机串口通讯程序
(SN75LBC184 used to achieve the RS232C and RS485 serial port conversion, so that PC-equipped master-slave multi-machine communications, to achieve a number of single-chip data acquisition terminal component of communication and management. Agreed a simple and effective string mouth communication protocol, according to this design a single-chip communication protocol with the PC-Serial communication program)