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This article is to share with you about the connection between external devices and machines in computers. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

There are only two ways to connect an external device to a machine, one is parallel, the other is serial. A parallel connection propagates multiple data streams at the same time through multiple channels, while serial connections transmit only one data stream at the same time.

Parallelism

Parallelism means that multi-bit data is transmitted through parallel lines at the same time, so that the speed of data transmission is greatly improved, but the length of parallel transmission is limited, because with the increase of length, the interference increases and the data is prone to error.

classification

Terminals communicate with other devices (such as other terminals, computers, and external devices) through data transmission. In data communication, according to the number of data bits transmitted each time, the communication mode can be divided into parallel communication and serial communication.

In parallel communication, all bits of data are transmitted at the same time, which can be carried out in parallel in words or bytes. Parallel communication is fast, but it uses many communication lines and high cost, so it is not suitable for long-distance communication. Various internal buses of a computer or PLC transmit data in parallel.

Characteristics

1, each data bit is transmitted at the same time, the transmission speed is fast, the efficiency is high, and it is often used in real-time and fast occasions.

2. The most basic way of information exchange in microcomputer system.

3. Parallel transmission of information does not require a fixed format.

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

5. The data width of parallel transmission can be 1 to 128 bits, or even wider, but the number of data bits requires as many data lines, so the transmission cost is high.

6. The anti-jamming ability of parallel communication is poor.

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

8. Transfer data one word at a time in terms of the word length of a computer, usually 8-bit, 16-bit, or 32-bit.

9. It is suitable for close, large and fast information exchange between external equipment and microcomputer.

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

Serial

Serial refers to the communication mode in which one bit of data is transmitted one at a time on the computer bus or other data channels, and the above single process is carried out continuously. It communicates on the serial port by transmitting several bits of data at the same time. Serial communication is used in long-distance communication and most computer networks. In these applications, cable and synchronization make the practical application of parallel communication difficult.

With its improved signal integrity and propagation speed, serial communication bus is becoming more and more common. Even in short-range applications, its advantages have begun to exceed that of parallel buses without serialization components (serializer), and solve the shortcomings such as clock offset (Clock skew), interconnection density (interconnect density) and so on. The upgrade from PCI to PCI Express is an example.

Compare

Between computers and between internal parts of a computer, communication can be carried out in a serial and parallel manner. A parallel connection propagates multiple data streams at the same time through multiple channels, such as wires, printed circuit cabling, and optical fiber, while serial connections transmit only one data stream at the same time.

Although serial connection can transmit less data than parallel data in a single clock cycle, and the transmission capacity of the former seems to be weaker than the latter, the actual situation is that serial communication can increase the communication clock frequency more easily than parallel communication. so as to improve the data transmission rate. There are some factors that allow serial communication to have a higher communication clock frequency:

No need to consider the phase difference of clock pulses in different channels (English: clock skew)

Serial connections require less physical media, such as cables and optical fibers, than parallel communications, thus reducing the volume of space

The problem of crosstalk can be greatly alleviated.

In many cases, serial communication becomes a better choice because of its lower deployment cost, especially in long-distance transmission. Many integrated circuits have serial communication interfaces to reduce the number of pins, resulting in cost savings.

Thank you for reading! This is the end of this article on "what are the connection methods between external devices and machines in the computer?" I hope the above content can be of some help to you, so that you can learn more knowledge. If you think the article is good, you can share it for more people to see!

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