Browse Prior Art Database

Regenerative Clock Technique for Servo Track Writers

IP.com Disclosure Number: IPCOM000102096D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 77K

Publishing Venue

IBM

Related People

Fowler, RV: AUTHOR [+2]

Abstract

The disclosed technique allows servo writing of a head/disk assembly after the covers are in place by means of the product head and without the use of an external position encoder disk. A single clock track is written at the outer diameter and divided into alternate A and B phases. The head is then stepped inwards half a track at a time using each phase alternately as a source of clock information from which servo information in the servo sectors preceding each data field and further clock signals in the alternate phase can be written. The half track steps ensure that the previously written clock information can be read. The technique dispenses with dedicated servo writer clock heads and associated mechanisms. Track to track phase errors are systematically compensated.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Regenerative Clock Technique for Servo Track Writers

       The disclosed technique allows servo writing of a
head/disk assembly after the covers are in place by means of the
product head and without the use of an external position encoder
disk.  A single clock track is written at the outer diameter and
divided into alternate A and B phases.  The head is then stepped
inwards half a track at a time using each phase alternately as a
source of clock information from which servo information in the servo
sectors preceding each data field and further clock signals in the
alternate phase can be written.  The half track steps ensure that the
previously written clock information can be read.  The technique
dispenses with dedicated servo writer clock heads and associated
mechanisms.  Track to track phase errors are systematically
compensated.

      A timing reference to the spindle of a magnetic disk file is
required to write the servo-tracks on the disk. Described is a
pattern of pulses that can be written in the data region of a sampled
servo file, which can be used to generate the timing reference for
writing the servo information. The example used is for a disk file
which cannot use a conventional clock head on the servo track writer
(STW) and instead uses an optical encoder on the spindle.  The file
speed is 3600 rpm and each track has 27 servo sectors each 61
microseconds long with a data region between each servo of 556
microseconds long.  The technique is as follows:
1.   The data region is divided into eight equal groups 69.5
microseconds long, each of which are alternatively A or B clock
areas, i.e., there are four A clock areas and four B clock areas
interleaved all aro...