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Chapter
3
1.
Control and Teletext Processing
1.1.
Control Processing
The following section covers the control processing
stage of the new 100Hz Euro 4 chassis which has
been introduced into the EURO 4 line up.
The Microprocessor IC1101 used on the EURO 4
chassis is the SDA5450 which performs the same
processing
tasks
as
microprocessor used on the first generation EURO 4.
This includes not only control processing but teletext
processing too.
Listed below is those changes:
1.1.1. Input Control
:
Pin 54 - Reset In
This input terminal is used as a power OFF reset by
the microprocessor IC1101 when the TV is switched
into standby. Without this power OFF reset the
microprocessor IC1101 has no way of knowing the
operational condition of the TV.
When the TV is switched OFF the operational data
from the digital processing ICs is lost, this means that
at switch ON this data has to be reloaded.
To be able to do this the microprocessor IC1101, has
to be reset so that at switch ON from standby the
operational data is reload into the digital processing
ICs. This is achieved with reset IC IC1105, which
monitors the 5V supply line via pin 2. When the 5V
supply falls to approximately 4.8V the reset IC IC1105
inputs a reset pulse via pin 54 of the microprocessor
IC1101.
:
Pin 58 - Slow1 / Pin 59 - Slow2
This circuit is designed so that it is possible to switch
over to AV operation from all programme locations to
the desired AV interface. The AV inputs being:
1.
AV1 21 pin scart socket allows composite video
and RGB signal input. Slow switching being
provide via pin 8 for composite video input.
under
taken
by
the
2.
AV2 21 pin scart socket also allows composite
video input providing slow switching control via
pin 8. AV2 also allows the input of an S-VHS
signal as does AV3 ( wide screen models only ).
The internal TV signal selection is performed by the
VPC IC1501 (located on the F-Board) which is
controlled by the microprocessor via I
placing an AV turn on voltage at pin 8 of the 21 pin
scart sockets, the relevant scart socket will be
automatically selected. This turn on voltage fed from
AV1 and AV2 pin 8 is fed to IC1101 pins 58 (AV1) and
59 (AV2) of the microprocessor.
Pin 8 of AV1 and AV2 scart sockets are also used to
allow IC1101 of the microprocessor to perform
automatic picture ratio selection between 4:3 and
16:9 formats during AV operation.
However, a pre-requirement for this would be for
example, the provision of a video recorder able to
process both picture formats. It has been established
that during play-back recorders with a picture format
of 4:3 supply an AV turn on voltage of 12V, and those
with an aspect ratio of 16:9 provide a turn on voltage
of 6V. These switching voltages fed from pin 8 of the
21 pin scart sockets are fed to the microprocessor
pins 58 (AV1) and 59 (AV2) via the potential divider
resistors R1131, R1128, and final R1127 to pin 59 for
AV2 selection. AV1 selection is fed via resistors
R1130, R1129 and R1126 to pin 58 of the
microprocessor IC1101.
The table shown below shows the required voltages
for aspect ratio selection.
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