ViewSonic E95 - Page 53

4.6.4 Brightness Control
Brightness (G1) is controlled by varying the DC voltage of VR601 and the IC601 pin23 (DAC)
voltage.
4.6.5 Blanking CKT
From IC301 pin6 and IC501 pin6 vertical blanking pulse are fed to the base of Q501 and via P604
pin3. The blanking pulse O/P is coupled to horizontal blanking pulse by Q614. Horizontal & vertical
blanking pulse are fed to [C601 pin27 and let video O/P Amp cut off during the period of horizontal
retraces. While mode change. IC301 pini5 will pull high to turn on Q612 (mute function) and Q613 will
be off. The G1 volt will down to -130V then CRT will cut off the video output.
4.6.6 CONTRAST, GAIN & BIAS CONTROL
The IC601 contains three gated single ended input black level clamp compurgators for brightness
control, three matched DC controlled attenuators for contrast control, and three DC controlled sub-
contrast attenuators providing gain trim capability for white balance.
All the DC control voltages are comes from IC601 internal (DAC) is controlled by IC301 Micro
controller via a serial bus. The IC601 DAC output pin24, 25, 26 for G.R.B (BIAS) controller.
4.6.7 DDC1/2B
1C604 (24LC21) can transmit continuously it's extended identification, "EDID" using DDC1
communication channel. In addition, the monitor can respond to a regrets for EDID, or complete VDIF, to
be transmitted using DDC2, level B commands. Pin6 (DSCL) is clock input for DDC 2B, pinS (DSDA) for
data input. Pin7 (V-sync) is clock input for DDC1 through V-sync.
In DDC1 data transfer (UNI-directional mode) the V sync input pin is used as input clock for data
transmission and SDA output pin as serial data line the SCL pin will hold high.
The DDC2B mode (BI - directional mode), BUS consists of two wires SCL is for the data
transmission clock and SDA is for the data link.
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