Clock recovery apparatus

1. A clock recovery apparatus, comprising:

a mask generator configured to generate a plurality of time masks using a multi-phase clock signal; and

a clock recovery unit comprising a mask selection unit configured to select one of the time masks and a logic gate configured to recover a clock from a data stream.

2. The clock recovery apparatus according to claim 1 , further comprising a phase locked loop or delay locked loop configured to generate the multi-phase clock signal.

3. The clock recovery apparatus according to claim 1 , wherein the logic gate comprises an AND gate receiving the data stream and the selected time mask.

4. The clock recovery apparatus according to claim 1 , wherein the mask selection unit comprises:

a delay calculator configured to estimate a delay of the clock in the data stream and generate a mask selection control signal; and

a mask selector configured to select one of the time masks according to the mask selection control signal.

5. The clock recovery apparatus according to claim 4 , wherein the delay calculator comprises:

two or more flip-flops configured to receive two or more time masks; and

delay calculation logic configured to receive outputs from the flip-flops, calculate the delay of the clock, and output the mask selection control signal.

6. The clock recovery apparatus according to claim 1 , wherein adjacent time masks have a same phase difference therebetween.

7. The clock recovery apparatus according to claim 1 , wherein adjacent time masks have different phase differences therebetween.

8. The clock recovery apparatus according to claim 1 , wherein the clock recovery apparatus has an operation period including a training period and an active period, and one of the time masks is selected during the training period.

9. The clock recovery apparatus according to claim 1 , wherein one of the time masks is selected when two neighboring time masks have different logic levels at a rising edge or a falling edge of the data stream.

10. A clock recovery apparatus, comprising:

a mask generator configured to generate a plurality of time masks using a multi-phase clock signal; and

a clock recovery unit configured to select one of the time masks and recover a clock from a data stream using the selected time mask, wherein one of the time masks is selected when two neighboring time masks have different logic levels at a rising edge or a falling edge of the data stream.

11. The clock recovery apparatus of claim 10 , wherein the clock recovery unit further selects one of the time masks according to a delay of the time masks.

12. The clock recovery apparatus according to claim 11 , wherein the clock recovery unit selects one of the time masks based on a combination of the delay of the time masks and the clock in the data stream.

13. The clock recovery apparatus according to claim 12 , wherein the clock recovery unit comprises:

a mask selection signal generator configured to generate a mask selection control signal based on the combination of the delay of the time masks and the clock in the data stream; and

a mask selector configured to select one of the time masks according to the mask selection control signal.

14. A method of recovering a clock signal from a data stream having an embedded clock, comprising:

generating a plurality of time masks from a multi-phase clock signal; and

selecting one of two adjacent time masks according to a delay of the time masks and a transition of the data stream between the two adjacent time masks, wherein the adjacent time masks are separated by 1/N of a unit of information, and N is an integer of at least two; and

recovering a clock from the data stream using the selected time mask.

15. The method according to claim 14 , further comprising generating the multi-phase clock signal from a phase locked loop or a delay locked loop.

16. The method according to claim 14 , wherein the unit of information is a data bit.

17. The method according to claim 14 , wherein recovering the clock from the data stream comprises logically combining the data stream and the selected time mask.

18. The method according to claim 17 , wherein logically combining the data stream and the selected time mask comprises receiving the data stream and the selected time mask in an AND gate.

19. The method according to claim 14 , wherein selecting the one of two adjacent time masks is based on a combination of the delay of the time masks and the clock in the data stream.

20. The method according to claim 19 , wherein selecting one of two adjacent time masks further comprises:

generating a mask selection control signal based on the combination of the delay of the time masks and the clock in the data stream; and

selecting the one of two adjacent time masks according to the mask selection control signal.