FUJITSU Disk Drives MHJ2181AT - Manual (Page 65)

Theory of Device Operation
4-14 C141-E088-01EN
4.7 Servo Control
The actuator motor and the spindle motor are submitted to servo control. The
actuator motor is controlled for moving and positioning the head to the track
containing the desired data. To turn the disk at a constant velocity, the actuator
motor is controlled according to the servo data that is written on the data side
beforehand.
4.7.1 Servo control circuit
Figure 4.6 is the block diagram of the servo control circuit. The following
describes the functions of the blocks:
Figure 4.6 Block diagram of servo control circuit
(1) Microprocessor unit (MPU)
The MPU includes the DSP unit, and the MPU starts the spindle motor, moves the
heads to the reference cylinders, seeks the specified cylinder, and executes
calibration according to the internal operations of the MPU. Main internal
operation of the MPU are shown below.
(6) (5)
(7)
(4) (3)
Power
Amp