摘  要：针对不具备串行同步总线硬件接口的单片机系统设计，提出并实现了I2C总线和SPI接口的总线复用方法。设计采用软件模拟总线时序的方法，扩展不同串行同步总线接口的外设芯片，设计了I2C总线接口PCF8583和SPI接口MAX7219外设串行同步总线间的数据线复用方法，有效解决单片机系统设计I/O口线资源不足的问题。系统运行结果表明，不同串行同步总线间的复用方法，不仅理论上是可行的，实际运行中外设器件的工作也稳定可靠，为串行同步总线的扩展提供了一种良好的解决方案。
关键词：串行同步总线；I2C总线；SPI接口；复用；模拟时序

Abstract: Aiming at the design of SCM system hardware without serial synchronous bus hardware interface, proposed and realized the I2C（Inter-Integrated Circuit） and SPI （Serial Peripheral Interface） expansion and multiplexing method. Using software method to simulate the serial synchronous bus timing, SCM system design of the I2C bus peripheral interface PCF8583 and the SPI peripheral interface MAX7219 multiplexing method, effectively solve the I/O resources shortage. System operation results show that different serial synchronous bus multiplexing method, not only in theory is feasible but the peripheral operation also stable and reliable, provides a good solution for the synchronous serial bus expansion problem.
Key words: synchronous serial bus; inter-integrated circuit; serial peripheral interface; multiplexing; simulating timing