Service manual

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.
Pin number Pin Name Pin Number Usage
21 P1.3 Key / Power on ,off
13 P3.4 NV_RAM (U4) SDA
14 P3.5 NV_RAM (U4) SCL
25 P1.7 Key_down
9 P6.3 Key_right
24 P1.6 Key_up
16 P6.2 Key_left
37 P4.1 Key_mute
34 P5.6 VGA connector
23 P1.5 Key_select
42 P5.3 LED_red
41 P5.4 LED_green
32 P6.6 LCD panel power1 on / off control
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