Acer AL718 Manual de serviço - Página 11

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Acer AL718 Manual de serviço

4. THEORY OF OPERATION

This section describes the function of the LCD monitor per functional block.
button board.
1. MB BOARD
The MB board is a four-layer, single-landed design with ground and internal planes provided.
The VGA cable is a signal cable that contains video signal, sync signal and DDCsignal from PC VGA adapter.
This system board consists of 3 functional areas : flat panel controller, flash ROM and LVDS transmitter.
1.1 Flat panel controller...... gm2120 (U8)
The heart of the system board is Genesis gm2120. The gm2120 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 sacling engine, OSD controller and on-chip microcontroller.
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) Hardware Reset ( Pin 5 )
Hardware Reset signal is generated by MAX809 (U10).It assert a reset signal at least 100 ms.
c) Analog to Digital Converter
The gm2120 chip has three ADC's (analog-to-digital converters), one for each color (red, green and blue)
The analog RGB signals are connected to gm2120 as described below
Pin Name
Red +
Red -
Green +
Green -
Blue +
Blue -
d) OSD :
The gm2120 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.
e) On-Chip Microcontroller (OCM)
The gm2120 on-chip microcontroller(OCM) serves as the system microcontroller.That is , it programs the
gm2120 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.
AL718
Pin Number
171
170
167
166
163
162
4-1