Differential Manchester encoding
Overview
Line code
In telecommunication, a line code is a code chosen for use within a communications system for baseband transmission purposes...
in which data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
and clock signal
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...
s are combined to form a single 2-level self-synchronizing
Synchronizing
In telecommunication, the term synchronizing has the following meanings:# Achieving and maintaining synchronism.# In fax, achieving and maintaining predetermined speed relations between the scanning spot and the recording spot within each scanning line....
data stream
Data stream
In telecommunications and computing, a data stream is a sequence of digitally encoded coherent signals used to transmit or receive information that is in the process of being transmitted....
. It is a differential encoding, using the presence or absence of transitions to indicate logical value. It has the following advantages over some other line codes:
- A transition is guaranteed at least once every bit, allowing the receiving device to perform clock recoveryClock recoverySome digital data streams, especially high-speed serial data streams are sent without an accompanying clock signal. The receiver generates a clock from an approximate frequency reference, and then phase-aligns to the transitions in the data stream with a phase-locked loop...
. - Detecting transitions is often less error-prone than comparing against a threshold in a noisy environment.
- Unlike with Manchester encoding, only the presence of a transition is important, not the polarity.
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