IC697CPX928  (Serial Peripheral Interface – Synchronous Peripheral Interface) bus is a synchronous serial communication interface specification used for short distance communication (mainly in embedded systems). Although there is no formal international standard, this interface protocol, invented by Motorola and supported by many manufacturers, has become a de facto standard and is widely used in various MCU processors SD card and LCD for data connection. Due to the lack of unified international standards, IC697CPX928  has introduced many different protocol options, such as different Word sizes; Each device has its own protocol definition, including whether it supports commands; Some devices only send, while others only receive; Some film selections are highly effective, while others are low effective; Some protocols send the lowest bit first.

Sometimes IC697CPX928  is also known as a four wire serial bus, mainly distinguished from 3-wire, 2-wire, and 1-wire serial buses. Although SPI can be accurately described as a synchronous serial interface, it is different from the synchronous serial interface (SSI) protocol. SSI is also a four wire synchronous serial communication protocol, but it uses differential signals and only provides a simple communication channel.