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The CLV Servo Circuit
Code
$04
DISC MOTOR START (Accelerate)
$05
DISC MOTOR CLV (CLV)
$06
DISC MOTOR BRAKE (Decelerate)
$07
DISC MOTOR STOP (Stop)
+
CLV
is the signal for accelerating the disk in the forward direction, while CLV
Depending on the commands from the microcontroller, one of the following four modes is selected: Accelerate,
decelerate, CLV, or stop. The CLV
MODE
CLV
Accelerate
High
Decelerate
Low
CLV
Pulse output
Stop
Low
* The CLV servo control command is such that the TOFF pin is low only when the CLV mode is in effect, and it is high
otherwise. The TOFF pin control by the command is only active when the CLV mode is in effect.
• CLV mode
In the CLV mode the rotation of the disk is detected from the HF signal, and a precise linear speed of rotation is
derived by exerting the respective forms on control when the internal modes of the DSP change. The PWM frequency
is 7.35 kHz. The V/P has a high output when the internal mode is the rough servo, and a low output when the internal
mode is phase control.
Internal mode
Rough servo (when the rotational speed is determined to be low)
Rough servo (when the rotational speed is determined to be high)
Phase control (when the PCK clock is running)
• Switching the rough servo gain
Code
$A8
DISC 8 cm Set
$A9
DISC 12 cm Set
When the internal mode is the rough servo, the CLV control gain for the 8 cm disk can be reduced by 8.5 dB from the
level for the 12 cm disk.
Pin 20: CLV+, Pin 21: CLV-, Pin 22: V/P
COMMAND
+
–
and CLV
outputs for each mode are as shown in the table below.
+
–
CLV
Low
High
Pulse output
Low
COMMAND
LC78626KE
RES = low
+
–
CLV
CLV
V/P
High
Low
High
Low
High
High
PWM
PWM
Low
RES = low
–
is the signal for decelerating the disk.
No. 5995-13/34
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