Fujitsu MAH3091MC - Enterprise 9.1 GB Hard Drive, Maintenance Manual

Page: 135 / 157

8 - 12 C141-E103-01EN
•
Preparation of servo mark detection
•
Gap
2) Servo mark area
Servo mark patterns are written in the servo mark areas and patterns are detected by the length
of the DC areas. The servo mark determines the starting point for detecting a position pattern
and gray code pattern.
3) Gap area
The gap area is located before and after the gray code area and position area. The gap area
prevents the misdetection of the gray code pattern or position pattern by releasing a
synchronization of the servo mark or delaying a reference counter.
4) Gray code area
The gray code is an encoded area which includes the head number, servo sector number and
cylinder information as gray code. Head position is recognized based on the cylinder
information embedded as a gray code pattern.
5) Position area
Information for recognizing head position is recorded in the position area. Head position in
cylinder unit is recognized by using the cylinder information in the gray code area, and head
position under one cylinder (resolution) is recognized by using the information in the position
area.
IGB DS Servo zone
Outer side of disk
Center of disk
OGB
Figure 8.5 Position of servo track
Data zone