In a single reception and transmission, the **data** frame is only 8 bytes. See Table 3 for the format of the **data** frame. Specifically, the first two bytes are respectively the **data** head and the command code, and the last byte is the end-of-string identifier 0xaa. As for the sent **data** frame, the meaning of the first two bytes remain the same, while the third byte is different from that of the received **data** frame.    Each reading and writing via SPI contains 16 bits: 1 bit for the select bit, 7 bits for the address and 8 bits for the data. The R/W select bit is used to identify the reading and writing operations. 1 stands for reading, and 0 stands for writing.