Philips CDR880 - Microcontroller and Electrical System Overview; Servo Microcontroller Coordination; Input Signal Path to Encoder; Digital Input Signal Processing

BASICS CDR/RW
17
In play-back mode. of a pre-recorded disc the total: wobble
processing is switched off and:the motorcontrot signal from
Decoder is used to control the turntable motor.
3.2.5 The Servo microcontroller
The Sarva microcontroller cesrdinatae all functions of the
laser control, servo-, AEGER-, Wobble-, Encoding- and
Decoding-processing. The-System controller actuates all
those procenel a?
3.3 “The Electrical part
The electrical part of the CD-Recorder/player can be split up
in the arrangements of the incoming audio signal which should
be prepared to be converted into the EFM-signal, and the
EFM-signal which have been read should be converted into
the audio output signal. The first function has been carried out
by the input part with the encoder path, the second by the
decoder path with the output part. Both parts are transporting
the digital data in the set. That's why this bus is often called
Data Path. On the overall blockdiagram at figure 13 all these
units have been drawn.
Blockdiagram
Waits
3.3.1 The input part of the circuit with the ENCODER path
In the CD Audio Recorder is in recording mode the electrical
input signal will be written to the disc. The encoder which
takes care of coding into EFM format wants to get an | 2s
digital input signal. That's why all input signals are converted
into the I7S format. The analogue signals are converted in an
A/D converter into this format. The optical or electrical digital
information at the input has to be converted to the | 25 signal
too. This happens in the Digital In circuit.
3.3.1.1 Digital In
Digital signals (optical or electrical), according to the Digital
Audio Interface, an IEC standard with bi-phase modulated
information, are converted in the Genera! Digital Input IC
(GDIN) into the Datapath I?S bus format. After this conversion
all subcode information has been sent to the pP to generate a
new subcode. On figure 25 the blockdiagram of this GDIN IC
is shown. The IC is able to perform a sample rate conversion
of digital signals. (SRC Mode) It can also read several serial
input formats in the IEC958 digital audio format. For that a full
Audio Digital Input Circuit (ADIC) is present. An internal digital
PLL circuit clocks the incoming signal jitter free.
cLo2
CLO3 CLO4
CONTROLLER
INTERFACE/
STAND-ALONE
CONTROL
a ieet
AL 7
Figure 25
Blockdiagram of the General Digital Input
B . PH I LI PS Service disc systems