Contents
What is clock and data recovery?
In serial communication of digital data, clock recovery is the process of extracting timing information from a serial data stream to allow the receiving circuit to decode the transmitted symbols. This is one method of performing a process commonly known as clock and data recovery (CDR).
Why is clock recovery needed?
The main goal when transmitting an optical/electrical signal from one point to the other is to conserve the signal integrity to avoid any loss of data. A key feature is the ability to transfer timing information from source point to destination point. This timing feature is called Clock Data Recovery.
In which communication clock signal is sent?
synchronous communication
In synchronous communication, the sender and receiver use clocks that are synchronised (kept in phase), usually using a phase-locked loop or dedicated clock wire. This ensures that the receiver is able to determine the centre of each data bit when decoding the data that has been sent.
How does clock recovery work in a computer?
Clock recovery is a common component of systems communicating over wires, optical fibers, or by radio. Some digital data streams, especially high-speed serial data streams (such as the raw stream of data from the magnetic head of a disk drive and serial communication networks such as Ethernet) are sent without an accompanying clock signal.
How is clock recovered from a data stream?
To generate the recovered clock, the receiver needs to phase align the reference clock to the transitions on the incoming data stream. This is called as Clock recovery. Sampling of that incoming data signal with recovered clock to generate a bit stream is called as Data recovery. Together, this is called Clock Data Recovery, or CDR.
What’s the difference between CDR and clock data recovery?
Sampling of that incoming data signal with recovered clock to generate a bit stream is called as Data recovery. Together, this is called Clock Data Recovery, or CDR. CDR is required to recover data from incoming data stream in the absence of any accompanying clock signal, without any bit errors due to over/under sampling.
How is a sampling clock used in clock recovery?
Or, a counter can be used that is driven by a sampling clock running at some multiple of the data stream frequency, with the counter reset on every transition of the data stream and the data stream sampled at some predetermined count. These two types of oversampling are sometimes called spatial and time respectively.