Phase locked loop for clock extraction in gigabit rate data communication links
First Claim
1. A structure for extracting a bit clock, a frame clock, and data from a data stream comprising:
- an input port for receiving said data stream wherein;
said data stream is grouped into consecutive frames of N bits, where N is an integer,each of said consecutive frames comprises at least two non-data bits, with two of said non-data bits being in consecutive bit positions and being of opposite logic values, the transition between said two non-data bits forming a master transition, said master transition being of the same polarity and located in the same position in each of said frames;
said consecutive frames are grouped into one or more groups of frames; and
an integral number of said consecutive frames at the beginning of each of said groups of frames constitute a training sequence comprising only said master transition and one transition of opposite polarity;
an output port for providing extracted data;
bit clock means for providing a bit clock signal which is adjusted in response to a binary clock control signal to match said data stream in frequency and phase;
a clock control source comprising;
an input lead connected to said input port;
a frame clock means for generating a frame clock signal having a frequency equal to 1/N times the bit clock signal frequency as means for selecting one of every 2N-th transition in said bit clock signal; and
an output lead supplying said binary clock control signal, said binary clock control signal changing its level at most once per frame, and having a first binary value when said selected bit clock transition occurred before said master transition and a second binary value when said selected bit clock transition occurred after said master transition, said binary clock control signal, when of said first binary value influencing said bit clock means to decrease the frequency of said bit clock and when of said second binary value influencing said bit clock means to increase the frequency of said bit clock; and
sampler means having an input lead connected to receive said data stream, a clock input lead for receiving said bit clock signal, and an output lead for providing said extracted data on said output port.
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Abstract
A family of Phase Locked Loop circuits and methods for extraction of a clock signal from a digital data stream, for example as received by a data communication link receiver is taught. The circuits of this invention are particularly advantageous in gigabit rate links where the propagation delay of digital circuits is comparable to the duration of a bit time interval and therefore careful matching of clock extracting and data sampling circuit topology is required. In certain embodiments, a frequency detector is included making the structure suitable for use in situations where there is a large fractional difference between the incoming data rate and the free running frequency of the receiver VCO. Such is the case when both the incoming data rate and the receiver VCO frequency are not controlled by a precision element such as a crystal or a Surface Acoustic Wave device.
103 Citations
35 Claims
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1. A structure for extracting a bit clock, a frame clock, and data from a data stream comprising:
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an input port for receiving said data stream wherein; said data stream is grouped into consecutive frames of N bits, where N is an integer, each of said consecutive frames comprises at least two non-data bits, with two of said non-data bits being in consecutive bit positions and being of opposite logic values, the transition between said two non-data bits forming a master transition, said master transition being of the same polarity and located in the same position in each of said frames; said consecutive frames are grouped into one or more groups of frames; and an integral number of said consecutive frames at the beginning of each of said groups of frames constitute a training sequence comprising only said master transition and one transition of opposite polarity; an output port for providing extracted data; bit clock means for providing a bit clock signal which is adjusted in response to a binary clock control signal to match said data stream in frequency and phase; a clock control source comprising; an input lead connected to said input port; a frame clock means for generating a frame clock signal having a frequency equal to 1/N times the bit clock signal frequency as means for selecting one of every 2N-th transition in said bit clock signal; and an output lead supplying said binary clock control signal, said binary clock control signal changing its level at most once per frame, and having a first binary value when said selected bit clock transition occurred before said master transition and a second binary value when said selected bit clock transition occurred after said master transition, said binary clock control signal, when of said first binary value influencing said bit clock means to decrease the frequency of said bit clock and when of said second binary value influencing said bit clock means to increase the frequency of said bit clock; and sampler means having an input lead connected to receive said data stream, a clock input lead for receiving said bit clock signal, and an output lead for providing said extracted data on said output port. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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Specification