Abstract:
A method and apparatus for performing adaptive calibration of a disk assembly and for determining an offset value to compensate for differences in servo head (28) to data head (29) distance from a nominal value. The present invention has particular application in a relative track count servo system where absolute track position is not known from a reading of the servo track (15) itself. In the preferred embodiment, a single head assembly (27) having both a data head and a servo head is utilized. The distance between the data head center and the servo head center must be known so that a disk (10) written on one drive assembly can be read in another drive assembly. This distance is a nominal value but may vary due to manufacturing tolerances. In the present invention, both the data and servo heads are utilized to establish a servo anchor reference track and to determine an offset correction value to compensate for variations in the servo/data head spacing. A dual reference track architecture is employed on the disk surface. The data head is positioned over the first reference track (11) and centered to within a desired accuracy.
Abstract:
At a first frequency (30), flux transitions are achieved which result in large excursions of the information signal. The first frequency approximates the maximum frequency at which such excursions can occur. A second higher frequency (89) is utilized to create small or no excursions. At this second frequency, a complete flux transition is not achieved. Information is represented by the presence or absence of excursions. An adaptive, self-compensating scheme, which is self-adjusting in real time and provides for recovery of the nominal flux transition independent of the information pattern, is utilized. Data recovery is qualified through the use of an excursion detection scheme which compares variations in the tracking peak (91) detect value with the input signal separated by an excursion threshold value. When the input waveform falls below the adaptive threshold voltage (94), a data transition is defined.