In addition to conventional RGB and row field synchronization, the 12th pin (CRTSDA) and 15th pin (CRTSCL) are I ² C buses used for DDC communication to read the display's EDID. If VGA has no output, first check if the DB-15 cable is intact and confirm if the system recognizes the monitor (which can be detected through OS display settings).
3.2 Backlight inverter connection (CN1 and CN5, 4-position pin arrangement)
Pin signal description
1 BRTADJ brightness adjustment PWM/voltage (controlled by panel knob)
2 GND Ground
3 ENBKL backlight enable (high level effective, controlled by S1 and APM)
4+12VFP+12V power supply (with 1.1A self recovery insurance)
Important: If an external inverter is used, it is necessary to confirm whether its enable logic (high/low valid) matches. If ENBKL is not connected, the backlight may remain on or off. The brightness adjustment function requires the inverter to support BRTADJ input, otherwise the knob is invalid.
3.3 LCD panel main interface (CN3, 44 pins)
This interface gathers power, data, and control signals. Key power pins:
+12VFP (1st and 12th pins): for backlight inverter, same as CN1/CN5.
FPVDD (3rd, 5th, 6th, 43rd, 44th, etc.): LCD logic power supply (voltage determined by JP3), enabled by ENFPVDD (22nd pin).
FPVEE (pins 21 and 42):+3.3V bias voltage (for VGH/VGL of DSTN or TFT), enabled by ENFPVEE (pin 20).
Data signal: FPD0~FPD23 correspond to RGB data, SHFCLK is the pixel clock, FLM (frame synchronization), LP (row synchronization), M/DE (data enable) and other synchronization signals need to match the panel timing.
Safety reminder: All power outputs are equipped with self recovery fuses, but short circuits may still cause voltage drops, resulting in display flashing. It is recommended to measure the impedance between FPVDD and GND with a multimeter before powering on to ensure there is no short circuit.
3.4 Post I/O Routing (8217R only)
The J2 connector of 8217R leads the above LCD signals (FPD0~FPD23, SHFCLK, FLM, LP, ENBKL, etc.) to the rear transition board for easy connection to the rear panel of the chassis through backplane wiring. However, J2 also includes GA4~GA0 address lines (for geographic addressing), so their use in non-standard backboards is strictly prohibited.
Key points and compatibility strategies for driver installation
The driver installation steps for the SM721 controller on Windows 2000/98/NT are detailed in the manual, but there are still several error prone steps during actual deployment.
4.1 Manual Installation of Windows 2000/XP
The system defaults to loading standard VGA drivers, which cannot utilize hardware acceleration and LCD dual display functions. Correct steps:
Go to the Device Manager and find "Video Controller (VGA compatible)" or "Silicon Motion Lynx 3DM" (if the wrong driver has been identified).
Select 'Update Driver', point to the CD path HIPDRV VGA SM721 WIN2K, and select smisetup. info.
The system may prompt 'Digital signature not found', select 'Continue' to proceed.
After installation, it needs to be restarted to take effect, and then the mirroring or expansion mode of CRT and LCD can be set in the display properties.
Common problem: If you still cannot select a resolution higher than 1024 × 768 after installation, please check if the BIOS has disabled the LCD - when LCD is disabled, VGA can support up to 1600 × 768 resolution 1200@16bit However, the dual display function has failed; On the contrary, when LCD is enabled, the resolution of CRT is limited to 1280 × 1080 1024@24bit .
4.2 Windows 98/ME Installation
The process is similar, but please note that the path is WIN9X and the driver file is smi. inf. Windows 98 has weak support for plug and play, sometimes requiring manual specification of the 'display adapter' type and installation from disk.
4.3 Windows NT 4.0
It needs to be changed from "Display" ->"Settings" ->"Display Type" in the control panel, with the path being SM721 WT40. The NT system is sensitive to IRQ and memory conflicts. If there is a blue screen after installation, it is necessary to check the allocation of PCI bus main control resources.
4.4 Linux and OS/2 support
The disc contains the corresponding drivers, but the manual does not provide detailed information. It is recommended to refer to the official open-source frame buffer driver of Silicon Motion or contact ADLINK to obtain patches that are compatible with the kernel version.
Application of panel indicator lights and calibration functions
The front panel provides two LEDs and a brightness knob for quick diagnosis of display status:
Green LED (LCD On): It lights up when the LCD signal and backlight enable are both active. If the light goes off, even if VGA has output, the LCD will definitely go black. At this point, it should be checked whether S1 has been accidentally touched or whether the system has entered APM sleep.
Amber LED (power-saving mode): It lights up when the LCD is manually turned off by S1 or the system automatically enters power-saving mode. If the module uses a "VGA only" BIOS, the LCD will always turn off and this light will remain on - this is a normal behavior, not a fault.