5. SPI程序设计与电路仿真

SPI是全双工的同步串行接口，一根SPI总线可以连接多个主机和多个从机，但是在同一时刻只允许有一个主机操作总线。在数据传输过程中，主机总是向从机发送一个字节的数据，而从机也是总是向主机发送1个字节数据（主机通过MISO接收数据）。

定义74HC595片选端口,通过PINSEL0、PINSEL1寄存器设置SPI引脚接口，通过设置IO0DIR驱动74HC595的接口，初始化SPI接口，发送显示数据，片选清零寄存器，等待SPIF置位，等待数据发送完毕。使用while循环，发送数据显示数据，运用延时程序使显示更加稳定易用。

-5. SPI program design and circuit simulation SPI is a full duplex synchronous serial interface, an SPI bus can connect multiple hosts and multiple slaves, but at the same time allowing only one host operating bus. During data transfer, the master to the slave always sends a byte of data, but also the slave always sends a byte to the host data (host via MISO receives data). Definition 74HC595 chip select port via PINSEL0, PINSEL1 register setting SPI pin interface, driven by setting IO0DIR 74HC595 interface to initialize the SPI interface to send display data, chip select register is cleared, waiting for SPIF bit waiting for data transmission is completed. Use a while loop to send data display data, using delay routine makes the display more stable and easy to use.