4.7 Servo Control

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 recovery

Servo mark

Gray code

Burst EVEN1

Burst

ODD

Burst EVEN2

PAD

Figure 4.8 Servo frame format

(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) PAD

This area is used as a gap between servo and data.

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Fujitsu MHV2060AS, MHV2080AS, MHV2040AS manual Servo frame format

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