Data recovery apparatus for the synchronized recovery of first and second channels of data signal portions from first and second parallel transmission media, the first and second channels of data signal portions being transmitted in synchronism into the first and second transmission media, said data recovery apparatus comprising:
- voltage-controlled oscillator (VCO) means, responsive to a VCO control signal, for generating a VCO clock signal;
- phase comparator and latch means, responsive to the VCO clock signal and the first and second channels of data signal portions, for generating data corresponding to data of the first and second channels of data signal portions at a predetermined phase of each clock period of the VCO clock signal;
- control means responsive to said phase comparator for generating the VCO control signal effective to maintain a stable relatively low phase difference between the VCO clock signal and each of the first and second channels of data signal portions;
- said phase comparator and latch means includes means for providing a phase difference control signal which represents respective phase differences between the VCO clock signal and the first and second channels of data signal portions;
- and
- said control means generating the VCO control signal in response to the phase difference control signal;
- said phase difference control signal includes first and second control signals which represent phase differences between the VCO clock signal and the first and second channels of data signal portions, respectively;
- said phase comparator and latch means comprising:
- first phase Comparator means, responsive to the VCO clock signal and the first channel of data signal portions, for providing the first control signal;
- and
- second phase comparator means, responsive to the VCO clock signal and the second channel of data signal portions, for providing the second control signal;
- said VCO clock signal consists of a periodic succession of alternate rising and falling clock edges, each successive VCO clock period including a rising and a falling clock edge, the first and second channels of data each consisting of a succession of alternate rising and falling edges;
- said first phase comparator means including
- first means for initiating a first sampling signal at each rising and falling edge of the first channel of data signal portions, each said first sampling signal having a first predetermined duration,
- first delay means for delaying said VCO clock signal by one-half the first predetermined duration to provide a first delayed clock signal, and
- means, responsive to the first delayed clock signal and the first sampling signal, for providing the first control signal according to a phase difference between a selected one of the rising and falling clock edges of the first delayed clock signal and the first sampling signal;
- and
- said second phase comparator means including
- second means for initiating a second sampling signal for each rising and falling edge of the second channel of data signal portions, each said second sampling signal having a second predetermined duration,
- second delay means for delaying said VCO clock signal by one-half the second predetermined duration to provide a second delayed clock signal, and
- means, responsive to the second delayed clock signal and the second sampling signal, for providing the second control signal according to a phase difference between a selected one of the rising and falling edges of the second delayed clock signal and the second sampling signal;
- so that said control means generates the VCO control signal with a magnitude effective to control said VCO means to generate the VCO clock signal with the selected one of the rising and falling edges of each clock period occurring at or near the rising and falling edges of both the first and second channels of data signal portions.