Servo Frame Format; Figure 4.8 Servo Frame Format - Fujitsu MHV2120BH Product Manual

4.7.3 Servo frame format

As the servo information, the IDD uses the phase signal servo generated from the
gray code and servo EVEN and ODD. This servo information is used for
positioning operation of radius direction and position detection of circumstance
direction.
The servo frame consists of 5 blocks; write/read recovery, servo mark, gray code,
Burst EVEN1, Burst ODD, Burst EVEN2, and PAD. Figure 4.8 shows the servo
frame format.
Write/read Servo
recovery mark
(1) Write/read recovery
This area is used to absorb the write/read transient and to stabilize the AGC.
(2) Servo mark
This area generates a timing for demodulating the gray code and position-
demodulating the burst signal by detecting the servo mark.
(3) Gray code (including sector address bits)
This area is used as cylinder address. The data in this area is converted into the
binary data by the gray code demodulation circuit
(4) Burst Even1, Burst Odd, Burst Even2
These areas are used as position signals between tracks and the IDD control so
that target phase signal is generated from Burst Even and Burst Odd.
(5) Post code (MHV2120BH only)
This area is used for the precise correction of the servo information which is
recorded on the media.
(6) PAD
This area is used as a gap between servo and data.
C141-E224
Gray code Burst
EVEN1

Figure 4.8 Servo frame format

4.7 Servo Control
Burst Burst
ODD EVEN2
Post PAD
code
(MHV
2120BH
only)
4-17