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5.2 Intel 82855GME Graphics and Memory Controller Hub (GMCH)
DVOB and DVOC Port Common Signal Descriptions Digital Video Output C (DVOC) Port Signal Descriptions
Name Type Description Name Type Description
DVOBCINTR# I DVOBC Interrupt: This pin is used to signal an interrupt, typically DVOCD[11:0] O DVOC Data: This data bus is used to drive 12-bit RGB data on each
DVO used to indicate a hot plug or unplug of a digital display. DVO edge of the differential clock signals, DVOCCLK and DVOCCLK#.
ADDID[7:0] I ADDID[7:0]: These pins are used to communicate to the Video BIOS This provides 24-bits of data per clock period. In dual channel mode,
DVO when an external device is interfaced to the DVO port. this provides the upper 12-bits of pixel data.
Note: Bit[7] needs to be strapped low when an on-board DVO device DVOCD[11:0] should be left as left as NC (?Not Connected?) if not
is present. used.
The other pins should be left as NC. DVOCHSYNC O Horizontal Sync: HSYNC signal for the DVOC interface.
DVODETECT I DVODETECT: This strapping signal indicates to the GMCH DVO DVOCHSYNC should be left as left as NC (?Not Connected?) if not
DVO whether a DVO device is present or not. When a DVO device is used.
connected, then DVODETECT = 0. DVOCVSYNC O Vertical Sync: VSYNC signal for the DVOC interface.
DVO DVOCVSYNC should be left as left as NC (?Not Connected?) if the
signal is NOT used when using internal graphics device.
DVOCBLANK#O Flicker Blank or Border Period Indication: DVOCBLANK# is a
DVO programmable output pin driven by the GMCH.
When programmed as a blank period indication, this pin indicates
active pixels excluding the border. When programmed as a border
period indication, this pin indicates active pixel including the border
Analog CRT Display Signal Descriptions pixels.
DVOCBLANK# should be left as left as NC (?Not Connected?) if not
Pin Name Type Description
used.
VSYNC O CRT Vertical Synchronization: This signal is used as the vertical
DVOCFLDSTLI TV Field and Flat Panel Stall Signal. This input can be
CMOS sync signal.
DVO programmed to be either a TV Field input from the TV encoder or
HSYNC O CRT Horizontal Synchronization: This signal is used as the
Stall input from the flat panel.
CMOS horizontal sync signal.
DVOC TV Field Signal: When used as a Field input, it synchronizes
RED O Red (Analog Video Output): This signal is a CRT Analog video
the overlay field with the TV encoder field when the overlay is
Analog output from the internal color palette DAC. The DAC is designed for displaying an interleaved source.
a 37.5-§U equivalent load on each pin (e.g., 75-§U resistor on the DVOC Flat Panel Stall Signal: When used as the Stall input, it
board, in parallel with the 75-§U CRT load). indicates that the pixel pipeline should stall one horizontal line. The
RED# O Red# (Analog Output): Tied to ground. signal changes during horizontal blanking. The panel fitting logic,
Analog when expanding the image vertically, uses this.
GREEN O Green (Analog Video Output): This signal is a CRT analog video DVOCFLDSTL needs to be pulled down if not used.
Analog output from the internal color palette DAC. The DAC is designed for
a 37.5-§U equivalent load on each pin (e.g.,75-§U resistor on the
board, in parallel with the 75- §U CRT load).
GREEN# O Green# (Analog Output): Tied to ground.
Analog
BLUE O Blue (Analog Video Output) : This signal is a CRT Analog video
Analog output from the internal color palette DAC. The DAC is designed for
a 37.5-§U equivalent load on each pin (e.g., 75-
ohm resistor on the board, in parallel with the 75-§U CRT load).
BLUE# O Blue# (Analog Output): Tied to ground.
Analog
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