What are the methods of information transmission between microcomputers and external devices?

There are two methods of information transmission: 1. Serial communication method refers to the serial transmission of data between the computer host and peripherals and between the host system and the host system; serial communication has the characteristics of fewer transmission lines, Low cost features. 2. Parallel communication means that data is transmitted in groups on multiple parallel channels at the same time; parallel communication has the characteristics of simultaneous transmission of each data bit, fast transmission speed and high efficiency.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The information transmission methods between microcomputers and external devices include: serial communication method or parallel communication method.

Serial communication method

Serial communication refers to the connection between the computer host and peripherals and between the host system and the host system Serial transmission of data between devices. Using a data line, the data is transmitted bit by bit, and each bit of data occupies a fixed length of time. It only requires a few lines to exchange information between systems, and is especially suitable for long-distance communication between computers and computers and peripheral devices.

Serial communication has the characteristics of few transmission lines and low cost. It is mainly suitable for short-distance human-computer exchange, real-time monitoring and other system communication work. It can also achieve long-distance transmission with the help of the existing telephone network. , so the serial communication interface is a commonly used interface in computer systems.

• Use a data line to transmit data one by one.

• Generally speaking, long-distance communication uses serial transmission, and serial communication is also used between computers.

• Low cost and relatively simple.

Features:

The way data is transmitted bit by bit in sequence on a single one-bit wide transmission line is called serial transmission. line of communication. In parallel communication, one byte (8 bits) of data is transmitted from source to destination on 8 parallel transmission lines at the same time; in serial communication, data is transmitted one bit after another on a single 1-bit wide transmission line. Positions are transmitted sequentially. Such a byte of data must be transmitted bit by bit in sequence from low bit to high bit 8 times. It can be seen that the characteristics of serial communication are as follows:

1. Saving transmission lines, this is obvious. This feature is particularly important when communicating over long distances. This is also the main advantage of serial communication.

2. Data transmission efficiency is low. Compared with parallel communication, this is also obvious. This is also the main disadvantage of serial communication.

For example: to transmit a byte, if the time required for parallel communication is 1T, the time required for serial communication is at least 8T. It can be seen that serial communication is suitable for long-distance transmission, which can range from a few meters to thousands of kilometers. For long-distance, low-speed communication, serial communication is often the only option. Parallel communication is suitable for short-distance, high-speed data transmission, usually the transmission distance is less than 30 meters. It is particularly worth mentioning that the existing public telephone network is a universal long-distance communication medium. Although it is designed for transmitting sound signals, the use of modulation and demodulation technology can make the existing public telephone network system for serial data communication. Provide convenient and practical communication lines.

Parallel communication method

Parallel transmission refers to the simultaneous transmission of data in groups on multiple parallel channels. A transmission in which multiple data bits are transferred between devices simultaneously.

• Use multiple data lines to transmit data simultaneously in the form of groups.

• Generally speaking, the transmission between the computer, such as CPU and memory. Usually in the form of a bus, common bus widths are 8-bit, 16-bit, 32-bit, 64-bit, etc.

• High cost, suitable for computer internal communication.

In parallel communication, each bit of data is transmitted at the same time, and can be performed in parallel in units of words or bytes. Parallel communication is fast, but uses many communication lines and is costly, so it is not suitable for long-distance communication. Various internal buses of a computer or PLC transmit data in parallel.

Features

1. Each data bit is transmitted simultaneously, with fast transmission speed and high efficiency. It is mostly used in real-time and fast situations.

2. The most basic information exchange method in microcomputer systems.

3. Information transmitted in parallel does not require a fixed format.

4. The data transfer rate of the parallel interface is 8 times faster than the serial interface. The theoretical value of the data transfer rate of the standard parallel port is 1Mbps (megabits/second).

5. Parallel transmission The data width can be 1 to 128 bits, or even wider, but as many data lines are required as there are data bits, so the cost of transmission is high.

6. Parallel communication has poor anti-interference ability.

7. Data transmission within the integrated circuit chip, between components on the same plug-in board, and between plug-in boards in the same chassis are all in parallel.

8. Use the computer's word length, usually 8 bits, 16 bits or 32 bits as the transmission unit, to transmit one word length of data at a time.

9. Suitable for short-range, large-scale and fast information exchange between external devices and microcomputers.

10. Parallel data transmission is only suitable for short-range communication, usually the transmission distance is less than 30 meters.

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