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Browse Prior Art Database

Method to Minimize the Influence of Servo Unlock

IP.com Disclosure Number: IPCOM000118234D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Aida, T: AUTHOR [+3]

Abstract

Disclosed is a method to minimize the influence of servo unlock by keeping current Digital Analog Convertor Output (DAC OUT) and use the known function Dummy sector pulse.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 97% of the total text.

Method to Minimize the Influence of Servo Unlock

      Disclosed is a method to minimize the influence of servo unlock
by keeping current Digital Analog Convertor Output (DAC OUT) and use
the known function Dummy sector pulse.

      Until now, a default value to keep the actuator at middle zone
is set to DAC OUT when servo unlock occurs.  But when unlock occurs
at the outer or inner zone, the default DAC OUT takes a long time to
come back and flow the target track stably, like Fig. 1.  It is also
significant when the operation is write.  The Host gives up the write
command because a write abort error occurs continuously on many data
sectors due to the influence of servo unlock.

      Dummy sector pulse function is a well-known measure about servo
unlock.  But it is risky to use when the operation is write, because
Position Error Signal (PES) information has low reliability.  So,
there is a possibility to write an adjacent track when unlock occurs
at a previous servo (Fig. 2).

      To solve this condition, keep the previous DAC OUT of unlock
servo but not set default DAC OUT to minimize the influence before
next unlock, and use Dummy sector pulse against the next unlock when
the data sector to be written is apart from unlock servo to make the
PES information higher in reliability.

      By using both methods, keeping current DAC OUT and dummy sector
pulse, it is possible to perform write operation under highly
reliable conditions, as shown in Fi...