提出一种基于串行外设接口（serial peripheral interface，SPI）总线的双处理器间通信的数据链路层设计方法.该方法中的双向SPI总线具有占用引脚少(仅比SPI总线多一根线)、有完善的数据链路层协议控制的优点，能够保证数据透明地在双处理器之间进行传输.以一款带有显示单元的车身总线控制器为应用对象，采用ARM9和S12作为双处理器实现双向通信，并对这一通信方法的实现和应用情况进行描述.实验表明，采用该方法设计的协议比较完善，能够满足实际工程中的需求，对于其他SPI的应用也有很好的借鉴价值.

This paper proposes a data link layer design method for dual-processor communication based on serial peripheral interface (SPI) bus. Advantages of the two-way SPI bus in this design include using less pins (only one line more than the SPI bus) and perfect data link layer protocol control. These can ensure transparent data transfer between the two processors. An automotive body bus controller with a display unit was used as an application. It uses ARM9 and S12 as dual-processors to achieve two-way communication. Implementation and application of the method are described. Experiments show that the protocol is effective in engineering practices, and provides a reference to other SPI applications.