LC78681E Datasheet, PDF (9/23 Pages) Sanyo Semicon Device – Digital Signal Processor for Compact Disc Players

2. 2-byte Commands
LC78681E
The commands are executed on the falling edge of RWC.
Focus Servocontroller (pin 13: FOCS, pin 14: FST, pin 15: FZD and pin 57: LASER)
MSB
LSB
00001000
10100010
00001010
10001010
00000000
Command
FOCUS START #1
FOCUS START #2
LASER ON
LASER OFF
NOTHING
1. Laser Control
RES = low
2. Focus Start
When a Focus Start command (either 1 or 2) is issued, the pickup lens is first lowered as C1 discharges through FST
and then raised gradually as C1 is recharged by FOCS. FZD goes low when the focal point is reached, and FOCS is
reset and the focus servocontroller turned on when this signal is received.
After issuing this command, the microprocessor checks the DRF signal from the LA9210 to verify that focus has
been reached, and advances to the next step. If C1 recharges fully before focus has been reached, the Focus Start
command should be reissued to repeat operation of the focus servocontroller.
No. 4521-9/23