DIAMOND DV172
Manual de Servicio

DV172 LCD Monitor Service Guide Circuit Operation Theory
Interface Board

RX0 RX1 RX2 RXC Red Green Blue DDC DDC Vsync Hsync (H+V) Gm5120 A/D TMDS MCU Scaling OSD To LCD module

SCL SDA
ROM

FLASHEEPROM

DSCL DSDA

(a) Circuit operation theory: (The scaling IC used in DV172 is Genesis gm5120)
A basic operation theory for this interface board in Analog input signals processing, the scaling IC inside A/D converter will convert analog input signals of Red, Green and Blue to 8 bits digital signals of Red, Green and Blue, and for interface board in DVI-D(TMDS) digital input signals processing, the scaling IC inside TMDS receiver will convert TMDS signals to 8 bits digital signals of Red, Green and Blue. Then no matter input signals Analog or DVI-D(TMDS) format are, they have been converted to 8 bits digital Red, Green and Blue signals, and the scaling IC inside MCU and scaling control circuit will start to do timing signal detecting and calculating to output the proper LCD panel signals to LCD panel circuit. The timing signal detecting function in the scaling IC is to detect whether input H-sync, V-sync or digital pixel clock signals� status have been changed by host PC system, then it will do short-time picture blanking, signal processing and converting again if input signals have been changed. The scaling IC inside OSD circuit will be programmed to an OSD menu which can be showed on the screen to offer adjustable functions to end-users to control and adjust some picture settings by themselves. After the scaling IC internal signal processing is done, it will output the digital RGB data, the H-sync, V-sync, pixel clock and DE(data enable) signal to LVDS transmitter and then to LCD panel driver circuit. There are two kinds of EEPROM used in interface board, one is 24C02 which is used to store DDC
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