Characteristics of Serial Communication Technology and Introduction of Three Isolation Techniques

Serial communication technology refers to a communication method in which both sides of the communication are carried out bit by bit and follow the sequence. In serial communication, the data is transmitted in sequence in bits, and each bit of data occupies a fixed length of time, and a few communication lines can be used to complete the exchange of information between systems, especially suitable for computers and computers, and between computers and peripherals. long-distance communication. Serial communication is mostly used for serial communication of data between systems (multi-master control system), between devices (master control device and auxiliary devices), and between devices (master control CPU and function chip) to realize data transmission and sharing. .

Serial communication technology refers to a communication method in which both sides of the communication are carried out bit by bit and follow the sequence. In serial communication, the data is transmitted in sequence in bits, and each bit of data occupies a fixed length of time, and a few communication lines can be used to complete the exchange of information between systems, especially suitable for computers and computers, and between computers and peripherals. long-distance communication. Serial communication is mostly used for serial communication of data between systems (multi-master control system), between devices (master control device and auxiliary devices), and between devices (master control CPU and function chip) to realize data transmission and sharing. .

In parallel communication, one byte (8-bit) data is transmitted from source to destination simultaneously on 8 parallel transmission lines; while in serial communication, data is transmitted one-by-one on a single 1-bit wide transmission line bit-sequential transmission. Such a byte of data needs to be transmitted 8 times in sequence from low to high. It can be seen that the characteristics of serial communication are as follows:

1. Save the transmission line, which is obvious. This feature is especially important when communicating remotely. This is also the main advantage of serial communication.

2. The data transmission efficiency is low, compared with parallel communication, which is also obvious. This is also the main disadvantage of serial communication.

Due to its working characteristics (bit-wise transmission is susceptible to interference, long-distance information exchange), applications (industrial control in harsh environments, outdoor, etc.), level matching between devices (the working levels of devices on both sides are inconsistent, etc.) , corresponding isolation protection is required. The main isolation methods are as follows:

(1) Discrete device isolation technology: The discrete device isolation method mainly uses a reasonable combination of resistors and transistors to match the level between input and output. It is a conventional and effective method to realize the double-side level conversion by using the switching function of the MOS tube. This isolation method is generally common ground isolation, which only completes level conversion to protect the device function and is not electrically isolated between systems.

(2) Photocoupler isolation technology: Photocoupler is a kind of device that uses light as the medium to realize electrical signal transmission. Since the electrical signals on both sides of the optocoupler are completely isolated, and the interior uses light as the transmission medium, the isolation between the input/output of the optocoupler can complete the isolated transmission of unidirectional signals, which is widely used in digital circuits.

(3) New isolation technology: With the rapid development of products, new devices emerge in an endless stream. A number of mainstream chips have developed different types of digital isolators such as capacitive isolation, magnetic coupling isolation, and radio frequency isolation.

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