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e Pull-in Servo
This servois used to pull the spindle motor speed into a
specified number of revolutions. With a cycle of 8.6436
MHz reckoned as T, we can get "22T" (synchronous sig-
nal) as the maximum inversion interval of an EFM signal
at the specified
number
of revolutions.
Therefore,
determine the EFM signal's maximum inversion inter-
val and compare it with "22T" so that we can detect
whether the motor speed is higher or lower than the
specified number of revolution.
EFM SIGNAL MAX.
INVERSION INTER-
VAL
"21T" and below
MOTOR
SPEED
MDF
MDR
TERMINAL | TERMINAL
L(Z)
high
L(Z)
L(Z)
L(2)
"23T" and above
low
Z: High impidamce
e Test Mode
STOP
KICK or STOP
KICK
Rough servo
¢ Rough Servo
This servo is used for the high-speed access in which
the carriage is moved at a high speed, with focus servo
ON and tracking servo OFF.
® Steady Servo
This servo is used to maintain the spindle motor speed
at a specified number of revolutions.
It is outputted as a result of comparing the phase be-
tween WFCK/4 and RFCK/4 or between WFCK/8 and
RFCK/8.
e Application Servo
This is the CLV servo mode available during the normal
operation. In the EFM demodulator block, every WFCK/
16 is sampled to determine whether or not the frame
synchronizing signal coincides with an output of the in-
ternal frame counter. As a result, a signal is generated to
show whether or not they are coincident. Once this sig-
nal has been found not incident in eight consecutive
cycles, the status is first determined
asynchronous.
Under any other conditions, the status is deemed syn-
chronous. The CLV application servo mode automati-
cally selects the pull-in servo
in the asynchronous
status and the steady servo in the synchronous status.
This feature is not employed in the present system.
Pull-in servo
BRAKE
STOP
Rough servo
POWER
Tracking close
ON
Focus
closed
FOCUS CLOSE
instruction
e Normal Mode
KICK or
STOP
Pull-in servo
KICK
Tracking
closed
Focus
closed
Power ON
80
Tracking
POWER
opened
OFF
Tracking jump,
POWER OFF
flaw, single jump
instruction
Pull-in servo
BRAKE
STOP
EJECT Key ON
Power OFF
Function OFF
Track
searched
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