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4) Spindle Servo System

The spindle servo has the following modes.

1 Kick :

This mode is used for accelerating the disc rotation

during setup.

2 Offset :

(a) After the kick is over in the setup, this mode is

turned on until changing to rough servo mode.

(b) When focus is lost during play, this mode is

turned on until the focus is restored.

Both of the above are used for maintaining the disc

rotation rate near to the specified rate.

3 Applicable servo :

The CLV servo mode is turned on for the normal

operations.

In the EFM demodulation block, the frame sync sig-

nal and internal counter output signal are sampled

for every WFCK/16 and a signal is produced for indi-

cating whether or not they are matching.

They are determined to be asynchronous only when

this signal fails to match 8 times in succession. In all

other cases, above two signals are assumed to be

synchronous. In the applicable servo mode, the

retracting servo is automatically selected if the two

signals are synchronous. If not, the regular servo is

automatically selected.

4 Brake :

This mode is turned on when stopping the spindle

motor.

The microcomputer outputs the brake voltage

through the servo LSI. The LSI monitors the EFM

waveform and, if its longest pattern exceeds a cer-

tain interval (if the rotation is sufficiently slow), the

flag is set the LSI and the microcomputer turns off

the brake voltage. When the flag is not up within a

specified period time, the microcomputer switches

the mode from the brake to the stop mode, and

maintains this mode for a fixed period of time. If this

stop mode is continued for a fixed period of time,

the disc will be ejected.

5 Stop :

This mode is used for powering on the system and

the eject operation. When this mode is turned on,

voltage across the spindle motor is 0V.

6 Rough servo :

This mode is used for when the carriage feed (car-

riage mode for the long search, etc.) is turned on.

The linear speed is calculated from the EFM wave-

form and high or low level is entered to the spindle

equalizer. In the test mode, this mode is also used

for the grating check.

IC201 UPD63711GC

SPEED ERROR SIGNAL

DSP

DIG.

EFM

DAC

SIGNAL

BLOCK

PHASE ERROR SIGNAL

Fig.18 : SPINDLE SERVO MOTOR BLOCK DIAGRAM

YPM-2306ZF

IC301

BA5985FM

SOP

SPINDLE

MOTOR

SOM