Patent ID: 6115199
Filing Date: 2000-09-05
Classification: G11B

Abstract:
A circuit preventing servo sectors in a magnetic disk from being overwritten due to misdetection of a servo address mark in a disk drive including a rotating data storage disk having a plurality of concentric data tracks and servo sectors embedded within the data tracks, and a transducer positioned to read data from a data track selected from said concentric data tracks, said circuit comprising:a controller controlling operations of said disk drive and controlling detection of the servo sectors including the servo address mark contained therein;a servo address mark detector detecting the servo address mark from data read from the disk and generating therefrom a servo address mark detection signal;a reference pulse generator generating reference pulses to obtain servo detection timing in response to the servo address mark detection signal;a system clock outputting system clock signals;a main counter counting system clock signals upon receipt of said reference pulses;a data sector end pulse generator generating a data sector end signal when a number of system clock signals counted by said main counter reaches a first predetermined value loaded by said controller;a servo address mark detection window generator generating a servo address mark detection window signal upon receipt of said data sector end signal and generating a pseudo servo address mark signal upon misdetection of the servo address mark during a detection period defined by said servo address mark detection window signal;a pseudo servo address mark pulse counter reset by said servo address mark detection signal counting the pseudo servo address mark signals generated by said servo address mark detection window generator to generate a counting pulse when a number of system clock signals counted by said main counter exceeds a second predetermined value;a delay and search flag bit generator generating, in response to the counting pulse, a servo address mark search select signal for delayings said servo detection timing and generating a search flag bit transferred to said controller; anda servo address mark search mode controller generating a servo address mark search start signal and disable signal according to said servo address mark search select signal provided by said delay and search flag bit generator, said disable signal being received by said main counter, said servo address mark search start signal being received by said servo address mark detector.