LC78621E Datasheet, PDF (17/34 Pages) Sanyo Semicon Device – Compact Disc Player DSP

LC78621E
• Track jump modes
The table lists the relationships between acceleration pulses, deceleration pulses, and the braking period.
Command
Standard track jump mode
a
b
c
New track jump mode
a
b
c
1 TRACK JUMP IN (OUT) #1 233 µs
233 µs
60 ms
233 µs
233 µs
60 ms
0.5 track
1 TRACK JUMP IN (OUT) #2 _{jump period}
233 µs
60 ms
0.5 track
jump period
0.5 track
jump period
60 ms
0.5 track
1 TRACK JUMP IN (OUT) #3 _{jump period}
233 µs
This period does 0.5 track
not exist.
jump period
0.5 track
jump period
This period does
not exist.
1 TRACK JUMP IN (OUT) #4 ^{0.5 track}
jump period
233 µs
60 ms; TOFF is
low during
the C period.
0.5 track
jump period
0.5 track
jump period
60 ms; TOFF is
low during
the C period.
2 TRACK JUMP IN (OUT) None
None
None
1 track
jump period
1 track
jump period
This period does
not exist.
4 TRACK JUMP IN (OUT)
2 track
jump period
466 µs
60 ms
2 track
jump period
2 track
jump period
60 ms
16 TRACK JUMP IN (OUT)
9 track
jump period
7 track
jump period
60 ms
9 track
jump period
9 track
jump period
60 ms
32 TRACK JUMP IN (OUT)
18 track
jump period
14 track
jump period
60 ms
18 track
jump period
14 track
jump period
60 ms
64 TRACK JUMP IN (OUT)
36 track
jump period
28 track
jump period
60 ms
36 track
jump period
28 track
jump period
60 ms
72 track
128 TRACK JUMP IN (OUT) _{jump period}
56 track
jump period
60 ms
72 track
jump period
56 track
jump period
60 ms
256 TRACK CHECK
TOFF goes high during the period
when 256 tracks are passed over.
The a and b pulses are not output.
60 ms
TOFF goes high during the period
when 256 tracks are passed over.
The a and b pulses are not output.
60 ms
TRACK JUMP BRAKE
There are no a or b periods.
60ms
There are no a and b periods.
60 ms
Note: 1. As indicated in the table, actuator signals are not output during the 256 TRACK CHECK function. This is a mode in which the TES signal is
counted in the tracking loop off state. Therefore, feed motor forwarding is required.
2. The servo command register is automatically reset after one cycle of the track jump sequence (a, b, c) completes.
3. If another track jump command is issued during a track jump operation, the content of that new command will be executed starting immediately.
4. The 1 TRACK JUMP #3 and 2 TRACK JUMP modes do not have a braking period (the C period). Since brake mode must be generated by an
external circuit, care is required when using this mode.
When the LC78621E is used in combination with the LA9230M or the LA9231M, since the THLD signal is generated by the LA9230M or the
LA9231M, the THLD pin (pin 25) will be unused, i.e., have no connection.
5. Tracking brake
The chart shows the relationships between the TES, HFL, and TOFF signals during the track jump C period. The TOFF signal is extracted from the
HFL signal by TES signal edges. When the HFL signal is high, the pickup is over the mirror surface, and when low, the pickup is over data bits.
Thus braking is applied based on the TOFF signal being high when the pickup is moving from a mirror region to a data region and being low when
the pickup is moving from a data region to a mirror region.
No. 5223-17/34