Philips 20PT643F Service Manual page 117

I 2 C-Bus
The main control system, which consists of the microprocessor part of the UOC (7200),
is linked to the external devices (tuner, NVM, MSP, etc) by means of the I
internal I C-bus is used to control other signal processing functions, like video
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processing, sound IF, vision IF, synchronization, etc.
User Interface
The 'L01.1U AC' uses a remote control with RC5 protocol. The incoming signal is
connected to pin 67 of the UOC.
The 'Top Control' keyboard, connected to UOC pin 80, can also control the set. Button
recognition is done via a voltage divider.
The front LED (6691) is connected to an output control line of the microprocessor (pin
5). It is activated to provide the user information about whether or not the set is working
correctly (e.g., responding to the remote control, normal operation (USA only) or fault
condition)
In- and Output Selection
For the control of the input and output selections, there are three lines:
STATUS1. This signal provides information to the microprocessor on whether a
video signal is available on the SCART1 AV input and output port (only for
Europe). This signal is not connected in NAFTA sets.
STATUS2. This signal provides information to the microprocessor on whether a
video signal is available on the SCART2 AV input and output port (only for
Europe). For sets with an SVHS input it provides the additional information if a
C-bus. An
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