Pioneer DEH-M8047ZT/UC Service Manual page 90

1
A
Output from FD terminal
FE controlling signals
B
FSS bit of SRVSTS1 resistor
C
Fig. 1.2.2 Timing chart for focus close operations
1.2.2 Tracking servo system
In the tracking servo system, the digital equalizer block is used as its main equalizer. The figure 1.2.3 shows the block
diagram of the tracking servo system.
(a) Track jump
Track jump operation is automatically performed by the auto-sequence function inside the LSI with a command from
D
the microcomputer. In the search mode, the following five track jump modes are available: 1, 4, 10, 32, and 32*3
In the test mode, 1, 32, and 32*3 track jump modes, and carriage move mode are available and can be switched by
selecting the mode.
For track jumps, first, the microcomputer sets about half the number of tracks to be jumped as the target. (Ex. For 10
track jumps, it should be 5 or so.) Using the TEC signal, the microcomputer counts up tracks. When the counter
reaches the target set by the microcomputer, a brake pulse is sent out to stop the lens. The pulse width is determined
by the microcomputer. Then, the system closes the tracking loop and proceeds to the normal play. At this moment, to
make it easier to close the tracking loop, the brake circuit is kept ON for 50msec after the brake pulse, and the tracking
servo gain is increased.
In the normal operation mode, the FF/REW operation is realized by continuously repeating single jumps about 10
E
times faster than the normal single jump operation.
(b) Brake circuit
The brake circuit stabilizes the servo-loop close operation even under poor conditions, especially in the setting-up
mode or track jump mode. This circuit detects the lens-moving direction and emits only the drive signal for the oppo-
site direction to slow down the lens. Thus, this makes it easier to close the tracking servo loop. The off-track direction
is detected from the phases of the TEC and MIRR signals.
F
8
1
2
Search start
A blind period
You can ignore this for blind periods.
RFOK signals
2
3
The broken line in the figure is assumed in the case
without focus servo.
The status of focus close is judged from the statuses
of FSS and RFOK after about 10mS.
CX-3057
3
4
4