FUJITSU MHT2060AT - Manual (Page 70)

Theory of Device Operation
4-18 C141-E192-01EN
4.7.3 Servo frame format
As the servo information, the IDD uses the two-phase servo generated from the
gray code and servo A to D. This servo information is used for positioning
operation of radius direction and position detection of circumstance direction.
The servo frame consists of 6 blocks; write/read recovery, servo mark, gray code,
servo A to D, and PAD. Figure 4.8 shows the servo frame format.
Figure 4.8 Servo frame format