Data-Side Servo Data Format; Servo Frame - Fujitsu MAB3091FC Series Maintenance Manual

5.7.3

Data-side servo data format

To detect an offset of the data surface against to the servo surface, a servo frame is embedded
between the data area on each data surface. The servo demodulator performs the offtrack
compensation by demodulating the servo signal on both servo surface and data surface. There
are 31 servo frames in one revolution on the data surface. Figure 5.10 shows the servo frame
configuration.
(1) Write/read recovery area
The write/read recovery area absorbs the transient of the demodulation signal generated at
switching the operation from writing to servo-reading the data area.
(2) Servo mark area
As same as the servo mark area on the servo surface, the servo mark pattern is detected by
using a pulse polarity and time interval. The servo mark determines the starting point for
detecting a position and gray code pattern.
(3) Gap 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) 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.
(5) Gray code area
A head and cylinder information are gray-coded and recorded in the gray code area.
W/R recovery
Servo
Gap
Position
mark
9.6 µs (MAAxxFC, MABxxFC)
8.0 µs (MACxxFC)
Figure 5.10 Servo frame
C141-F028-01EN
Gap Gap
Gray code
5 - 19