In order to ensure effective communication, according to the physical characteristics of electricity, transmission medium and requirements of serial port equipment, it is determined that the maximum transmission rate of RS232 can only be 1 15200, and then it is gradually divided into 57600, 28800 and 19200. In order to adapt to these rates, the corresponding crystal oscillator frequency is designed.

Serial communication refers to a communication mode in which data is transmitted bit by bit between peripherals and computers through data signal lines, ground lines and control lines. This communication method uses fewer data lines, which can save communication costs in long-distance communication, but its transmission speed is lower than parallel transmission.

Serial port is a very common device communication protocol on computer. Most computers (excluding laptops) include two serial ports based on RS-232. Serial port is also a common communication protocol for instruments. Many GPIB-compatible devices also have RS-232 ports. At the same time, serial communication protocol can also be used to obtain the data of remote acquisition equipment.