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(a) The track jump operation is automatically performed by the auto-sequence function inside the LSI with a command
from the CPU of the LSI. For the track jumps used in the search mode, a single track jump and four to 100 multi-track jump
are available in this system. In the test mode, out of these track jumps, 1, 32, and 32 * 3 track jumps, as well as carriage
A
move can be performed and checked in mode selection. In a track jump, the CPU of the LSI sets about half the number of
the total tracks to jump (about five tracks for a 10-track jump), and the set number of tracks are counted using the TEC
signal. By outputting the brake pulse for a certain period of time (set by the CPU of the LSI) from the time the set number
is counted, and stopping the lens, the tracking loop can be closed so that the normal play can be continued.
Also, in order to facilitate closing of the tracking loop in a track jump, the brake circuit is kept ON for 50 msec, after the
brake pulse is stopped, for increasing the tracking servo gain. The FF/REW action in the normal operation mode is
realized by performing single jumps consecutively. The speed is approximately 10 times faster than in the normal mode.
(b) Brake circuit
Since the servo loop is not closed very well in the setup mode and track jump mode, the brake circuit is used for stabilizing
B
the servo-loop close operation. The brake circuit detects the direction in which the lens moves, and outputs only the drive
signal for the direction opposite to the movement to slow down the lens, thereby stabilizing the tracking servo-loop close
operation. Additionally, the off-track direction is determined from the TEC and MIRR signals, as well as their phase
relation.
C
D
Fig.1.2.4 Single-track jump
E
F
10
1
2
BRAKE
TD
t1
KICK
TEC
T. BRAKE
EQUALIZER
GAIN NORMAL
T. SERVO
CX-3195
2
3
t2
ON
OFF
GAIN UP
NORMAL
OPEN
CLOSED
3
4
4
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