Prima PH50D8, Service Manual

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SCALER is confirmed.
3.2. Block diagram of AD9887 is shown below
Finally the video signals of different channels are sent respectively to V PORT and G PORT of main
processing chip PW181 for processing. PW181 has such processing capabilities as “picture out of
picture”, “picture in picture”, “multiple pictures”. So long as the signals come respectively from V PORT
and G PORT, they automatically become “picture out of picture”, “picture in picture”. PW181 has the
function of SCALER, which means it can conduct format conversion for the input signals of different
format to enable it to meet the requirement of the screen for format and finally output the signal in the
form of 24 bit RGB.
The standard of interface for PDP screen is LVDS (low voltage differential signal). So the digital
RGB signal output from PW181 still needs to be converted into LVDS signal by the conversion interface
chip of LVDS - N602 DS90C385 (This chip may vary with the manufacturer of the screen). This
converted signal is in turn fed to the screen for driving purpose. The output of N602 is four pairs of
differential signal and one pair of clock signal. If any pair of signal is abnormal then the image is affected
to be abnormal for example, a certain color may become abnormal. The PWRDOWN signal output from
PW181 is used to control the operation of N602, which works under low electric level.