As a widely used chip in embedded system, ARM9 processor generally has no more than three serial ports that it results in the difficulty to meet requirements of the system of multi-serial communication. By analysis of the serial port expansion' s issue of the design for the vehicle-mounted intelligent terminal based on ARM9 processor, it offers proposals for making use of a chip which could expand single serial port to five serial ports--GM8125 to implement serial port expansion, and the means of the delaminating deign for the serial communication to optimize the stability and efficiency of the system. And at last the feasibility of the precept has been validated by realizing the multi-serial communication of the GPS and GPRS modules with the computer.%目前ARM9处理器在嵌入式系统中得到了广泛应用,但是其通常只有3个及其以下的串口,对于需要多串口通信的系统难以满足要求;因此通过对基于ARM9处理器车载智能终端设计中遇到的多串口扩展问题进行了分析研究,提出了利用具有将单串口扩展为5串口功能的串口扩展芯片GM8125实现多串口扩展的方案,并在串口通讯中采用了分层设计的方法,提高了系统的稳定性和运行效率；并且利用GPS和GPRS模块实现与计算机多串口的通信,验证了方案的可行性.
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