A data and clock recovery system adapted for use with RZ data. In one embodiment a phase detector provides phase information for low to high data signal transitions only. In another embodiment a clock recovered from rising transitions is mixed with a clock recovered from falling transitions to form a recovered clock signal.
1. A return-to-zero (RZ) recovery system comprising:
first recovery unit configured to receive a data signal and identify a first type of data transition and determine a first phase information when the first type of data transition is identified;
second recovery unit configured to receive the data signal and identify a second type of data transition and determine second phase information when the second type of data transition is identified; and
wherein the first recovery unit generates a first recovered clock signal based on the determined first phase information and the second recovery unit generates a second recovered clock signal based on the determined second phase information; and
further comprising an interpolator configured to generate a third recovered clock signal based on the first recovered clock signal and the second recovered clock signal; and
wherein the data signal is a RZ data signal and the system further comprises a sampling unit and a filter, the filter configured to convert the RZ data signal into a non-return-to-zero (NRZ) data signal and provide the NRZ data signal to the sampling unit.
2. The system of claim 1 wherein the sampling unit samples the data signal using the third recovered clock signal from the interpolator.
3. A return-to-zero (RZ) recovery system comprising:
first recovery unit configured to receive a data signal and identify a first type of data transition and determine a first phase information when the first type of data transition is identified; and
second recovery unit configured to receive the data signal and identify a second type of data transition and determine second phase information when the second type of data transition is identified; and
wherein the first recovery unit generates a first recovered clock signal based on the determined first phase information and the second recovery unit generates a second recovered clock signal based on the determined second phase information; and
wherein the data signal is a RZ data signal and the system further comprises a sampling unit and a filter, the filter configured to convert the RZ data signal into a non-return-to-zero (NRZ) data signal and provide the NRZ data signal to the first recovery unit.
4. The system of claim 3 wherein the second recovery unit is disabled.