Signal Board; Device Control - Loewe Q2500B Serviceanleitung

Technology of Q 2500 colour TV set

4 Signal board

Mounted on the signal board, which is linked
to the basic board via connectors, are all the
necessary building blocks for device control,
interface switching, video, audio and videotext
processing.
These are:
- The device control with computer circuit,
operating software and the EAROM for the
storing of system data and customer spe-
cific calibration values.
- Production of system cycle frequency nec-
essary for a digital design.
- The digital IC's necessary for picture signal
processing.
- The video/deflection processor for the pro-
duction and synchronization of control
pulses.
- Digital audio processing for analogue trans-
ferred information and NICAM decoding.
- The teletext decoder, integrated into the
SDA 6000, with page memory, in which up
to 3000 text pages, according to design,
can be saved and which also generates the
OSD for the user control.
- The signal and interface selection by corre-
sponding IC's controllable via the I²C bus.
- Optional IC's for video processing, picture
in picture.
Document Q 2500

4.1 Device control

Full device control is implemented by a Sie-
mens 16 bit processor (SDA 6000) together
with Loewe operating software. The teletext
function is also integrated into the SDA 6000.
A standalone teletext processor is therefore
not necessary.
All processes in the digital signal preparation,
in the tuners and interface selection are
checked and controlled via a microcomputer
integrated into the SDA 6000. The processor
is also known as the CCU (Central Control
Unit).
It also supports the operating, tuning and
storage system on the frequency synthesis
principle. Without the DVB module there are
220 programme storage locations, and with
the DVB board there are 1470. The pro-
gramme locations are available for TV and
also for radio operation. The total number of
stored programs must not exceed 220 (1470).
For the AV inputs six additional places are
reserved.
Operating software is held in an external
EPROM. For the storage of c.r.t. and system
specific data there is an EAROM for device
control. The latter also contains programme
location information.
All three modules, CCU, EPROM and EAROM
are mounted on the signal board.
The remote maintenance sensor permits con-
trol of possible device functions. The chassis
tuning is also carried out by remote mainte-
nance.
For this, the sensor IC generates a serial data
word for each command that is transferred to
the receiver with a delay. This signal is de-
modulated by the IR receiver and prepared in
such a way that it can be sent directly to the
CCU as an RSIG signal.
The CCU detects the local operating com-
mands on a line by the different voltage levels.
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