Specifications

2000 Jun 26 32
Philips Semiconductors Product specification
Digital servo processor and Compact Disc
decoder with integrated DAC for video CD (CD7 II)
SAA7327
During reset (i.e. RESET pin is held LOW)
the RA, FO and SL pins are high-impedance.
7.14.10 LASER INTERFACE
The LDON pin (open-drain output) is used to switch the
laser off and on. When the laser is on, the output is
high-impedance. The action of the LDON pin is controlled
by the xtra_preset parameter; the pin is automatically
driven if the focus control loop is active.
7.14.11 RADIAL SHOCK DETECTOR
The shock detector (see Fig.22) can be switched on during
normal track following, and detects within an adjustable
frequency whether disturbances in the radial spot position
relative to the track exceed an adjustable level (controlled
by shock_level).
Every time the radial tracking error exceeds this level the
radial control bandwidth is switched to twice its original
bandwidth and the loop gain is increased by a factor of 4.
The shock detection level is adjustable in 16 steps from
0% to 100% of the traverse radial amplitude which is sent
to an amplitude detection unit via an adjustable band-pass
filter (controlled by sledge_parm1); lower corner frequency
can be set at either 0 or 20 Hz, and upper corner
frequency at 750 or 1850 Hz. The shock detector is
switched off automatically during jump mode.
7.15 Microcontroller interface
Communication on the microcontroller interface can be
set-up in two different modes:
• 4-wire bus mode: protocol compatible with SAA7345
(CD6) and TDA1301 (DSIC2) where:
– SCL = serial clock
– SDA = serial data
– RAB = R/W control and data strobe (active HIGH) for
writing to decoder registers 0 to F, reading status bit
selected via decoder register 2 and reading
Q-channel subcode
– SILD = R/W control and data strobe (active LOW) for
servo commands.
• I
2
C-bus mode: I
2
C-bus protocol where SAA7327
behaves as slave device, activated by setting
RAB = HIGH and SILD = LOW where:
–I
2
C-bus slave address (write mode) = 30H
–I
2
C-bus slave address (read mode) = 31H
– Maximum data transfer rate = 400 kbits/s.
It should be noted that only servo commands can be used
therefore, writing to decoder registers 0 to F, reading
decoder status and reading Q-channel subcode data must
be performed by servo commands.
handbook, full pagewidth
RE
MGC914
SHOCK
OUTPUT
HIGH-PASS FILTER
(0 or 20 Hz)
LOW-PASS FILTER
(750 or 1850 Hz)
AMPLITUDE
DETECTION
Fig.22 Block diagram of radial shock detector.