Fast locking clock and data recovery unit

1. A method of synchronizing a transmitter and a receiver, comprising:

receiving a transmitted serial data stream;

creating an N-bit data sample from the serial data stream; and

successively forming further N-bit data samples based on the N-bit data sample and examining each of the further N-bit data samples for a sentinel condition, until the sentinel condition is found; and

selecting a clock signal of a plurality of clock signals based on a location of the sentinel condition.

2. The method of claim 1 , further comprising recovering data from the serial data stream using the selected clock signal.

3. The method of claim 1 , wherein the selected clock signal is selected within 8 bit times.

4. The method of claim 1 , wherein the selected clock signal is selected within 8 bit times of creating the N-bit data sample.

5. The method of claim 1 , wherein creating the N-bit data sample from the serial data stream further comprises creating the N-bit data sample from the serial data stream over an M-bit period of the serial data stream.

6. The method of claim 1 , wherein the selected clock signal has an active edge approximately at the center of a data-eye of the serial data stream.

7. The method of claim 1 , further comprising locking the selected clock signal after selecting the clock signal of the plurality of clock signals based on said location of the sentinel condition.

8. The method of claim 7 , further comprising unlocking the selected clock signal in response to a predetermined unlocking signal.

9. The method of claim 8 , wherein the predetermined unlocking signal is one of an end of transmission character or a RESET signal.

10. A method of synchronizing a transmitter and a receiver, comprising:

receiving a transmitted serial data stream;

creating an N-bit data sample from the serial data stream; and

decoding the N-bit data sample by a ring decoding technique, wherein the ring decoding technique comprises:

creating a first code ring using the N-bit data sample, the first code ring having N ring-bit phase positions corresponding to N axis positions, with the N data bits of the N-bit data sample corresponding to one of the N ring-bit phase positions;

creating a p th Code Ring from a previous code ring using a preselected ring coding technique, the p th code ring having N ring-bit phase positions corresponding to N axis

positions, with N data bits of the p th code ring corresponding to the N ring-bit phase positions of the p th code ring;

analyzing selected ones of the N data bits of the p th code ring for the presence of a sentinel condition;

identifying a one of the N ring-bit phase positions of the p th code ring as being associated with the sentinel condition; and

selecting a clock signal based on the one of the N ring-bit phase positions.

11. The method of claim 10 , wherein the selected clock signal is selected within 8 bit times of creating the N-bit data sample.

12. A method of clock and data recovery from a transmitted serial data stream, comprising:

creating an N-bit data sample from the serial data stream, the N-bit data sample being recovered from the serial data stream using N clock signals at N differing phases;

decoding the N-bit data sample using a preselected ring decoding technique to determine which of the N clock signals to use for recovery of data from the serial data stream, wherein the preselected ring decoding technique comprises:

receiving a temporal snapshot having N data bits corresponding to the N-bit data sample;

creating a first code ring from the temporal snapshot, the first code ring having N ring-bit phase positions corresponding to N axis positions, each one of the N data bits corresponding to one of the N ring-bit phase positions;

creating a p th code ring from an immediately previous code ring using a preselected ring coding technique, the p th code ring having N ring-bit phase positions corresponding to N axis positions generally corresponding with the N axis positions of the first code ring, and one of the N data bits of the p th code ring corresponding to one of the N ring-bit phase positions of the p th code ring;

identifying a one of the N ringbit phase positions of the p th code ring as Φ X , Φ X indicating a ring-bit phase position as providing a sentinal condition;

determining a phase offset of:

Φ T =p/2, if p is even; or

Φ T =(p−1)/2, if p is odd;

selecting a corresponding recovered clock phase Φ R according to the relationship Φ R =Φ X +Φ T ; and

recovering data from the serial data stream using the corresponding recovered clock phase.