LC78620E Datasheet, PDF (11/34 Pages) Sanyo Semicon Device – Compact Disc Player DSP

LC78620E
• Command noise rejection
MSB
LSB
11101111
11101110
Command
COMMAND INPUT NOISE REDUCTION MODE
RESET NOISE EXCLUSION MODE
RES = low
q
This command reduces the noise on the CQCK clock signal. While this is effective for noise pulses shorter than
500 ns, the CQCK timings T_WøL, T_WøH, and t_setup (see pages 4 and 5, figures 1 and 2), must be set for at least 1 µs.
6. Focus Servo Circuit; Pin 16: FOCS, pin 17: FST, pin 18: FZD, pin 70: LASER
MSB
LSB
00001000
10100010
00001010
10001010
11111110
Command
FOCUS START #1
FOCUS START #2
LASER ON
LASER OFF
NOTHING
RES = low
q
The FOCS, FST, and FZD pins are not required when the LC78620E is used in combination with the LA9230M or
the LA9231M. FZD should be tied low when these pins are not used. The LA9230M and LA9231M focus start
command is identical to the LC78620E FOCUS START #1 command.
• NOTHING
This command can be used to initialize the LC78620E by inputting FE (hexadecimal). Note that 00 (hexadecimal)
is the reset command for the LA9230M and the LA9231M, and should be used with care since it clears the result
of the automatic adjustment process and returns these chips to their initial states.
• Laser control
The LASER pin can be use as an extended output port.
• Focus start
When the LC78620E is used in combination with the LA9230M or the LA9231M, the focus start operation is
executed completely on the servo side by commands from the control microprocessor. The following section
describes this operation when the LC78620E is used in combination with the LA9230M or the LA9231M.
When a focus start instruction (either FOCUS START #1 or FOCUS START #2) is input as a servo command,
first the charge on capacitor C1 is discharged by FST and the objective lens is lowered. Next, the capacitor is
charged by FOCS, and the lens is slowly raised. FZD falls when the lens reaches the focus point. When this signal
is received, FOCS is reset and the focus servo turns on. After sending the command, the microprocessor should
check the in-focus detection signal (the LA9210 DRF signal) to confirm focus before proceeding to the next part of
the program. If focus is not achieved by the time C1 is fully charged, the microprocessor should issue another
focus command and iterate the focus servo operation.
No. 5130-11/34