Browse Prior Art Database

File Level Servo Pattern Test Method

IP.com Disclosure Number: IPCOM000111830D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Misao, I: AUTHOR [+3]

Abstract

Disclosed is a servo pattern test method for a small size Hard Disk Drive (HDD) with a sector servo system. The servo pattern consists of a gray code portion and a wedge portion. Gray code shows the cylinder number, and the wedge shows the distance between the head gap and the track center. This test uses the wedge portion information, and the main characteristic of this test method is using the HDD card's own hardware and the test is carried out after manufacturing.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 83% of the total text.

File Level Servo Pattern Test Method

      Disclosed is a servo pattern test method for a small size Hard
Disk Drive (HDD) with a sector servo system.  The servo pattern
consists of a gray code portion and a wedge portion.  Gray code shows
the cylinder number, and the wedge shows the distance between the
head gap and the track center.  This test uses the wedge portion
information, and the main characteristic of this test method is using
the HDD card's own hardware and the test is carried out after
manufacturing.

      The Figure shows the summary of the servo pattern test in the
file level.  The gray code shows the cylinder number, and the wedge
A,B,C,D is converted to the offset from track center by the hardware
(Servo Analog IC).  This offset is called a Position Error Signal
(PES).  The following equation shows the relationship between the
wedge signal amplitude and PES digital value.

   PES = A/(A+B)*256
      where  PES  : The offset from track center (128 = track center)
             A, B : The amplitude of each wedge signal

      This PES value is used for the servo pattern test.  On each
track, the PES value is measured in the entire servo pattern and
compared to some criteria value (Pmax).  This comparison is carried
out in the Hard Disk Controller IC by hardware.  If all PES values
meet the criteria, the track is recognized as a good one, and the
next track is put to the test.  If at least one PES value does not
meet th...