Panasonic EURO 4 Chassis Technical Manual page 28

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13.1. Microprocessor Stage
13.1.1.Input Control
:
Pins 3/4 - XIN / XOUT
The internal oscillator of the CPU is synchronised with
an external 6MHz quartz crystal X1101 which is
connected to pins 3 and 4.
The Clock frequencies for the I
obtained from this frequency by internal dividing.
:
Pin 5 - Reset
During power On/Off operation, or during a fall in
voltage to the microprocessor IC1101, incorrect
operation may occur. To prevent this incorrect
operation the microprocessor
signal input via pin 5. This reset signal is provided by
the reset IC IC1104
microprocessor IC1101
voltage level has risen and become stabilised.
This reset IC IC1104 which is fed a 5V standby supply
is input via pin 2.
At switch On this supply is less than 4.3V which
results in the reset IC
microprocessor IC1101
condition until the supply voltage becomes greater
than 4.3V. At this point the reset line goes High and
the microprocessor IC1101
:
Pin 46 - HS
This input is used by the microprocessor for
synchronisation of the CVBS signal used for teletext
processing and display
:
Pin 47 - VS
This input is used by the microprocessor for
synchronisation of the CVBS signal used for teletext
processing and display.
:
Pin 54 - Reset In
This input terminal is used as a power OFF reset by
the microprocessor IC1101
standby. Without this power OFF reset the
microprocessor IC1101
operational condition of the TV.
When the TV is switched OFF the operational data
from the VDP IC601 and MSP
means that at switch ON the data has to be reloaded
back into the VDP IC601
To be able to do this the microprocessor IC1101, has
to be reset so that at switch ON from standby the
required operational data is reload back into the VDP
IC601 and MSP IC2101. This is achieved with reset
IC IC1105 which monitors the 5V supply line via pin
2. When the 5V supply falls to approximately 4.3V the
2
C bus system are also
IC1101 has a reset
pin 1, which keeps the
in a stable condition until the
IC1104 pulling pin 5 of the
Low, providing a stable
begins to operate.
as the TV is switched into
has no way of knowing the
IC2101 is lost, this
and MSP IC2101.
reset IC IC1105 inputs a reset pulse via pin 54 of the
microprocessor IC1101.
:
Pin 58 - Slow1 / Pin 59 Slow2
The 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 allowing composite
video and RGB signal input . Slow switching
being provide via pin 8 for composite video input.
2. AV2 21 pin scart socket also allows composite
video input providing slow switching control via
pin 8. AV2 also allows the input for S-VHS input
as does AV3 ( wide screen models only )
The internal TV switching is performed by the VDP
IC601 is controlled by the microprocessor via I
Bus 1. By placing an AV turn on voltage at pin 8 of
the 21 pin AV sockets, the relevant AV socket will be
automatically selected. This turn on voltage fed from
AV1 and AV2 pin 8 is fed to
(AV1) and 59 (AV2) 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
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 show a
turn on voltage of 6V. These switching voltages fed
from pin 8 of the 21 pin AV sockets and fed to the
microprocessor pins 58 (AV1) and 59 (AV2) are fed
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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IC1101 and the pins 58
formats. It has been
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