Abstract: Servo circuitry for counting tracks on an optical storage medium is disclosed. The servo circuitry is comprised of a differential phase detector and a digital phase-locked loop. The differential phase detector receives four signals from a quad-photodetector and correlates the four signals into a first correlation signal and a second correlation signal. The digital phase-locked loop receives an adjustable amplification value along with the positive correlation signal and the negative correlation signal. The digital phase-locked loop generates a track count signal based on the adjustable amplification value, the positive correlation signal, and the negative correlation signal. The track count signal represents track crossings on the optical storage medium. The digital phase-locked loop advantageously has an adjustable bandwidth based on the amplification value. The servo circuitry count tracks on both CDs and DVDs.

Abstract: Servo circuitry for correlating signals using a correlation data structure is disclosed. The servo circuitry is comprised of a setup system coupled to a correlation system that contains the correlation data structure. The setup system receives four signals and converts the signals to digital values. The correlation system takes the digital values and enters them into the correlation data structure. The correlation data structure yields a correlation value based on the digital values. The servo circuitry advantageously yields the correlation value that is a function of all four signals using the correlation data structure.

Abstract: An optical disk system comprises an optical disk device and control circuitry. The optical disk device stores user data and transfers an analog signal representing the user data to the control circuitry. The control circuitry sub-samples the analog signal to generate a sub-sampled signal. The control circuitry up-samples and re-times the sub-sampled signal using a control signal to generate an up-sampled and re-timed signal. A digital feedback loop in the control circuitry generates the control signal.