Sony XM-1502SX Training Manual page 59

A Video Decoder operating at a multiple of the color frequency (3.58MHz) will convert the input composite video
to the RGB information (output). Next, a high-speed switch inserts the OSD (On Screen Display) information into
the picture. Actually at each pixel, only one of the two pieces of information is allowed to appear on the LCD
panel. By mapping out the screen, Syscon can determine when the switch will toggle for a text OSD.
The Video Interface IC changes the picture characteristics to suit the user (contrast, brightness, color, etc) and
output the improved RGB signal to the LCD Assembly. The video Interface IC also reverses the polarity of the
RGB signals with the aid of FRPT/FRPU signals form the timing generator. Every other horizontal line is reversed
to prevent the LCD crystal from polarizing. A center DC voltage (Com) to the LCD panel marks the RGB signal's
point of inversion so the panel can separate the line of signals.
3) Timing Signals
Within the Video Decoder, an internal sync separator extracts the sync from the input video and sends it to the
Video Interface IC to blank above and left of the picture for consistency. More importantly, the H & V sync signals
are applied to the timing generator IC to synchronize the output timing pulses to the LCD assembly. By using the
horizontal sync signal input to lock the H VCO (high frequency oscillator), all the pulses output are locked to the
horizontal signal.
Normal
Inverted
Red
1
Blue
T
2
CH1!5.00 V=
CH2!5.00 V= MTB20.0us- 1.98dv ch2-
Figure B-3 - R & B signals to LCD
Normal
Inverted
iv
Appendix B - LCD