Philips 900 Series - Brushing Modes and Features; Brushing Modes and Routines; Product Features

CIRCUIT DESCRIPTION
the main microprocessor, generates an
\EC-958 signal, which is output via DIGITAL
OUT. The D/A converted audio signals LEFT
and RIGHT go to the appropriate analog
outputs via buffer amplifiers.
1.3.1.2 Data record, Aux record
In this operating mode, the audio data either
reach the DAIO directly via DIGITAL IN or
OPTICAL IN (digital source), or are first
digitized by the ADC (SAA7366) in case of an
analog source. Via I?S bus the digital audio
data are passed to SFC3. Here, the
broadband signal is separated into 32
subbands for left and right channels and a
PASC frame is generated.
During PASC encoding the adaptive and
scaling circuit (ADAS3) calculates the
tequired accuracy (bit allocation) and scale
factors of the PASC subband samples. The
subband samples are transferred to ADAS3
via FDAI input port. The ADAS has to collect
a complete frame of subband data before the
allocation and scale factor information can be
calculated. To have that information available
in the same time frame as the audio samples
are at the output, the subband filtered
samples are delayed. (Dependant to the
audio sample rate of 32, 44.1 or 48 kHz.) The
delayed samples are passed to the codec
part of SFC3 on the FDAO output port. This
bus between SFC3 and ADAS3 in the
recording mode is called the filtered data
interface.
For every PASC frame the ADAS3 calculates
a bit allocation and a scale factor table which
is transferred to the SFC3. Once scaled the
samples are re-quantized to reduce the
number of bits to correspond with the
allocation table, as calculated.
Synchronization, allocation and scale factor
are added in SFC3 to provide a fully PASC
data signal. These frames of data are now via
‘SBI?S-Bus’ sent to the DRP.
In the DRP the subband samples are
received in the subband serial PASC
interface.
In the recording mode Tape Formatting and
Error correction (TFE) part of this IC, the C1
and C2 error corrections are encoded and the
signal is formatted for tape transfer.
The sub-code data come via the L3-Bus to
the main microprocessor. Finally, the tape
frame data are passed on serially to the write
amplifier (TDA1319T), which drives the write
heads accordingly.
1.3.1.3 Data playback, Aux record
This operating mode is a combination of the
modes described above, and is used for
(subsequent) deletion or writing of markers on
the AUX track. The DRP continuously sends
sysinfo data to the main microprocessor, and
simultaneously generates AUX tape frames.
The tape frames generated by the DRP are
taken in serial form via WDATA to the write
amplifier, which drives the AUX write head
accordingly.
1.3.1.4 ACC playback
The analog head signals are first amplified by
the read amplifier, and linearised by a
magnetic feedback loop. A further filter stage
ensures an ideal frequency response. The
analog signal is then fed to the Dolby IC
CXA1331S, and any distortion is corrected.
The audio signal then goes via an amplifier
stage to the ADC, where it is digitized. The
DAIO generates (with the main
microprocessor) an [EC958 signal, which is
output via IEC OUT to DIGITAL OUT. The
digital audio data are passed on to the DAC
via the I’S-interface of the DAIO, D/A
converted, and taken to the appropriate
analog outputs via buffer amplifiers.
PHILIPS SOUND & VISION, BG AUDIO - Service Training