Fujitsu MAB3091FC Series Maintenance Manual page 45

The DSP accurately controls traffic positioning of each head using servo information on the
data surface.
(3) Spindle motor drive circuit
The spindle motor drive circuit drives the spindle motor. A drive current in the motor coil
generates a counter emf. The frequency of the counter emf is compared, by the DSP, with a
reference frequency derived by dividing the crystal oscillator frequency. The DSP uses the
result of the comparison to control the rotational frequency of the spindle motor.
(4) Controller circuit
The controller circuit has the following main functions:
•
Fibre channel control
•
Data buffering (4 MB, 1 to 16 segments)
•
SCSI protocol control and data transfer control
•
Sector format control
•
Serialization and deserialization (SER-DES)
•
ECC
•
Error recovery and self-diagnosis
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