计算机网络曼彻斯特编码,认识计算机网络通信中的曼彻斯特编码

谁践踏了优雅 2022-10-09 04:59 128阅读 0赞

Manchester Encoding

Manchester encoding (first published in 1949) is a synchronous clock encoding technique used by the physical layer to encode the clock and data of a synchronous bit stream. In this technique, the actual binary data to be transmitted over the cable are not sent as a sequence of logic 1's and 0's (known technically as Non Return to Zero (NRZ)). Instead, the bits are translated into a slightly different format that has a number of advantages over using straight binary encoding (i.e. NRZ).

Manchester encoding follows the rules shown below:

![1-137-jpg\_6\_0\_\_\_\_\_\_\_-510-0-0-510.jpg][1-137-jpg_6_0_-510-0-0-510.jpg]

![1-112-png\_6\_0\_0\_180\_890\_531\_126\_892.979\_1262.879-472-0-140-472.jpg][1-112-png_6_0_0_180_890_531_126_892.979_1262.879-472-0-140-472.jpg]

Note that in some cases you will see the encoding reversed, with 0 being represented as a 0 to 1 transition. The two definitions have co-existed for many years. The Ethernet Blue-Book and IEEE standards (10 Mbps) describe the method in which a Logic 0 is sent as 0 to 1 transition, and a Logic 1 as a one to zero transition (where a zero is represented by a less negative voltage on the cable). Note that because many physical layers employ an inverting line driver to convert the binary digits into an electrical signal, the signal on the wire is the exact opposite of that output by the encoder. Differential physical layer transmission, (e.g. 10BT) does not suffer this inversion.

The following diagram shows a typical Manchester encoded signal with the corresponding binary representation of the data (1,1,0,1,0,0) being sent.

The waveform for a Manchester encoded bit stream carrying the sequence

of bits 110100.

In the Manchester encoding shown, a logic 0 is indicated by a 0 to 1 transition at the centre of the bit and a logic 1 is indicated by a 1 to

[1-137-jpg_6_0_-510-0-0-510.jpg]: /images/20221005/7a96532c1066450bb78c7f019ac4925e.png
[1-112-png_6_0_0_180_890_531_126_892.979_1262.879-472-0-140-472.jpg]: /images/20221005/c768f829bb5545dd8c6731e0de1fffae.png