ViewSonic VX500PLUS-1 Service Manual page 35

Pin34 do mode detect (normal is LOW, ISP is HI)
Pin 35 controls the brightness of panel
Pin36, 37 control LED (orange and green) on /off
Pin38 control audio board 12V on/off
Pin40 control Buzzer on/off
Pin41 control ICM3 (regulator) on/off
Pin42 control ICM15, 16(LVDS Transmitter) on/off.
3. Image Processor
ICM5 (gm5010) is an all-in-one image processor for displays with a dual (analog and digital)
interface supporting resolutions up to XGA. It provides integrated ADC/PLL and a DVI compliant
TMDS receiver, a high quality zoom and shrink scaling engine, frame rate conversion, an on-screen
display (OSD) controller, a microprocessor and many other functions in a single device. This high
level of integration enables simple, flexible, cist effective solutions featuring fewer required
components. .
The gm5010 chip has three ADC's (analog-to-digital converters), one for each color (red,
green, and blue) and supports digital separate sync (HSYNC/VSYNC), digital composite sync,
and analog composite sync (also known as sync-on-green, or SOG). All sync types are
supported without the need for external sync separation / extraction circuits.
The gm5010 features four clock inputs. All additional clocks are internal clocks derived
from one or more of these four, using Direct Digital Synthesis (DDS).
TCLK is generated using an external crystal (recommended) or an external clock
oscillator.
(1) Input Clock (TCLK). The external connection to the oscillator is via the TCLK and
XTAL pads. A 14.3MHz crystal source is recommended, as internal PLL and logic circuits
derive the required clock frequencies from this single source by default. Other crystal
frequencies may be used, but require custom bootstrapping and programming. In lieu of using a
crystal oscillator, XTAL can be driven by a single-ended TTL/CMOS input clock (e.g. for
testing of the IC) – the TCLK pin should be grounded through a 2.7k pull down resistor to
maintain the correct duty cycle for the clock.
(2) TMDS Differential Input Clock (RC+ and RC-)
(3) Video Clock (VCLK) input pin
(4) Host Interface Transfer Clock (HCLK for 6-Wire nibble; SCL for 2-wire serial)
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VX500+-1