Servo system having track crossing detection for an optical disk drive system
AssigneeOak Technology, Inc.
InventorKai C. K. Sun
Life of this patent
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Abstract
A difference counter in a servo system includes RX signal processing circuitry, TX signal processing circuitry, and a latch. The RX processing circuitry includes a RX z-hold (zero order) circuit, a RX delay circuit coupled thereto, and a RX XOR logic circuit coupled thereto for producing an RX processed signal. The TX processing circuitry includes a TX z-hold circuit, a TX delay circuit coupled thereto, and a TX XOR logic circuit coupled thereto for producing an TX processed signal. The RX and TX processed signals are fed into the latch which, in response, generates a noise-free quarter track signal. Half and full track signals are generated therefrom to further process the signal track information.
Claims2
In a tracking servo system having a track equalizer for processing track error signal, and a feed motor/pickup unit assembly coupled to track equalizer for producing a quadrature signal RX and a tracking error crossing signal TX in response to the tracking error signal, a difference counter coupled to the feed motor/pick up unit and to the track equalizer for providing track information based upon a quarter track signal, the difference counter comprising:
- a RX z-hold circuit (206) which receives said RX signal;
- a RX delay circuit (210) coupled to said RX z-hold circuit;
- a RX XOR logic circuit (212) coupled to said RX z-hold circuit and to said RX delay circuit;
- a TX z-hold circuit (214) which receives said TX signal;
- a TX delay circuit (216) coupled to said TX z-hold circuit;
- a TX XOR logic circuit (218) coupled to said TX z-hold circuit and to said TX delay circuit;
- and
- a latch (220) coupled to said RX XOR logic circuit and to said TX XOR logic circuit for generating said quarter track signal.
In a disk drive system for retrieving data disposed on a plurality of tracks formed on a disk, a method for detecting the number of tracks crossed comprising the steps of:
- (a) generating a quarter track signal comprising the steps of:
- providing a first quadrature signal RX at a first time;
- providing a second RX signal at a subsequent time;
- generating a Rtrig signal by performing a XOR logical function on said first and second RX signals;
- providing a first tracking error crossing signal TX at a first time;
- providing a second TX signal at a subsequent time;
- generating a Ttrig signal by performing a XOR logical function on said first and second TX signals;
- providing a latch circuit having a set input, a reset input, and an output;
- supplying said Rtrig signal to said set input;
- supplying said Ttrig signal to said reset input;
- generating an output from said latch circuit;
- (b) therefrom, generating a half track signal;
- (c) generating a full track signal using the Ttrig signal, RX signal, and TX signal;
- and
- (d) indicating a track crossing when said full track signal is generated.
Dependencies are inferred from the claim text.