ViewSonic Corporation
Confidential - Do Not Copy
VX912-4
20
6.
THEORY OF OPERATION
This section describes the function of the LCD monitor per functional block.
This monitor includes MB board, power board and button board.
6.1
MB BOARD
The MB board is a two-layer, single-landed design with ground and internal planes provided. DC power from the power
board enter the board through a 6P connector. Other connector on the board is for button board .The VGA cable is a signal
cable that contains video signal, sync signal and DDC signal from PC VGA adapter. This system board consists of 4
functional areas : flat panel controller, MCU with flash ROM , power regulator .
6.1.1
Flat panel controller… MST8131A (U3)
The heart of the system board is MStart MST8131A. The MST8131A is a graphics processing IC for LCD monitor. It
provides all key IC functions required for LCD panel. On-chip functions include a high-speed triple-ADC , PLL, high
scaling engine, OSD controller.
a)
Clock Generation :
Crystal Input Clock (TCLK and XTAL). This is the input pair to an internal crystal oscillator and corresponding logic.
A 14.318 MHz crystal is recommended.
b)
Analog to Digital Converter:
The MST8131A chip has three ADC's (analog-to-digital converters), one for each color (red, green and blue) .The
analog RGB signals are connected to MST8131A as described
below
Pin Name
Pin Number
Red +
63
Red -
62
Green +
60
Green -
59
Blue +
58
Blue -
57
c).
OSD : The MST8131A has a fully programmable ,high-quality OSD controller. The on-chip static RAM(4096
words by 24 bits) stores the cell map and the cell definitions..
d).
MTV312 Micro controller: The MTV312 micro controller(MCU) serves as the system micro controller. It’s
programs the MST8131A and manages other devices in the system such as the keypad, the backlight, LED, audio
and non-volatile RAM. using general purpose input/output (GPIO) pins.
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