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This article mainly introduces what the data transmission methods are, the introduction in the article is very detailed, has a certain reference value, interested friends must read it!

The mode of data transmission is the way in which data is transmitted on the channel. According to the order of data transmission, it can be divided into "parallel transmission" and "serial transmission"; according to the synchronous mode of data transmission, it can be divided into "asynchronous transmission" and "synchronous transmission".

Data transmission mode (data transmission mode) is the way in which data is transmitted on the channel.

Sort in order

Parallel transmission is to transmit data in groups on more than two parallel channels at the same time. For example, using 8 units of code characters can be transmitted in parallel with eight channels, one channel transmitting one character at a time. Therefore, the character synchronization between the transceiver and the sender is realized without additional measures. The disadvantage is that there are many transmission channels, complex equipment and high cost, so it is seldom used.

Serial transmission is the transmission of data streams on one channel in a serial manner. This method is easy to implement. The disadvantage is that to solve the synchronization of code groups or characters between the receiver and the sender, additional synchronization measures are needed. Serial transmission is widely used.

Classify by way

In serial transmission, the measure taken by the receiver to correctly divide the transmitted characters from the serial data stream is called character synchronization. According to the different ways to realize character synchronization, there are two ways of data transmission: asynchronous transmission and synchronous transmission.

Asynchronous transmission each time a character code (5~8bit) is transmitted, each character code is preceded by a "start" signal with a length of 1 symbol, a polarity of "0", followed by a stop signal. When the second number of international telegram is used, the length of the stop signal is 1.5 symbols, when using international five numbers (see data communication code) or other codes. The stop signal length is 1 or 2 symbols, and the polarity is "1". Characters can be sent continuously or separately; when characters are not sent, stop signals are sent continuously. The start time of each character can be arbitrary (which is the meaning of asynchronous transmission), but each symbol is equal in length within the same character. The receiver detects the "start" signal that identifies a new character according to the jump ("1" → "0") from the stop signal to the start signal between characters, so as to correctly distinguish each character. Therefore, this method of character synchronization is also called start-stop synchronization. The advantage of this method is that the realization of synchronization is relatively simple, and the clock signals of both sender and receiver do not need accurate synchronization. The disadvantage is that 2~3bit is added to each character, which reduces the transmission efficiency. It is often used for low-speed data transmission in 1200bit/s and below.

Synchronous transmission transmits data signals at a fixed clock beat. In the serial data stream, the relative position between the letter symbols is fixed. In order to correctly distinguish the transmitted characters from the received data stream, the receiver must establish bit timing synchronization and frame synchronization. Bit timing synchronization is also called bit synchronization, and its function is to synchronize the bit timing clock signal at the receiving end of the data circuit termination equipment (DCE) with the input signal received by the DCE, so that the DCE can correctly judge each letter symbol from the received information flow and generate the received data sequence. There are two methods for DCE sender to generate timing: one is to generate timing in the data terminal equipment (DTE) and send the data of DTE to DCE according to the timing beat, this method is called external synchronization. The other is to use the bit timing inside the DCE to extract the data on the DTE side, which is called internal synchronization. For the receiving end of the DCE, the received data is sent to the DTE with the bit timing beat in the DCE. Frame synchronization is the correct grouping or framing from the received data sequence in order to correctly distinguish a character or other information. The advantage of synchronous transmission is that there is no need to add and stop symbols for each character, so the transmission efficiency is high. The disadvantage is that the implementation technology is more complex. It is usually used for data transmission at or above 2400bit/s rate.

The above is all the contents of this article "what are the ways of data transmission?" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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