
Intel
82845G/82845GL/82845GV GMCH Datasheet
35
Signal Description
2.6
Analog Display
Signal Name
Type
Description
HSYNC
O
3.3 V
GPIO
CRT Horizontal Synchronization:
This signal is used as the horizontal sync
(polarity is programmable) or “sync interval”.
VSYNC
O
3.3 V
GPIO
CRT Vertical Synchronization:
This signal is used as the vertical sync (polarity
is programmable).
RED
O
Analog
RED Analog Video Output:
This signal is a CRT Analog video output from the
internal color palette DAC. The DAC is designed for a 37.5
equivalent load on
each signal (e.g., 75
resistor on the board, in parallel with a 75
CRT load).
RED#
O
Analog
RED# Analog Output:
This signal is a truly differential analog video output from
the internal color palette DAC. Refer to the
Intel
Pentium
4 Processor in 478-
Pin Package and Intel
845G/845GL/845GV Chipset Platform Design Guide
for
routing recommendations. This signal is used to provide noise immunity.
GREEN
O
Analog
GREEN Analog Video Output:
This signal is a CRT Analog video output from
the internal color palette DAC. The DAC is designed for a 37.5
equivalent
load on each signal (e.g., 75
resistor on the board, in parallel with a 75
CRT
load).
GREEN#
O
Analog
GREEN# Analog Output:
This signal is a truly differential analog video output
from the internal color palette DAC. Refer to the
Intel
Pentium
4 Processor in
478-Pin Package and Intel
845G/845GL/845GV Chipset Platform Design
Guide
for routing recommendations. This signal is used to provide noise
immunity.
BLUE
O
Analog
BLUE Analog Video Output:
This signal is a CRT Analog video output from
the internal color palette DAC. The DAC is designed for a 37.5
equivalent
load on each signal (e.g., 75
resistor on the board, in parallel with a 75
CRT
load).
BLUE#
O
Analog
BLUE# Analog Output:
This signal is a truly differential analog video output
from the internal color palette DAC. Refer to the
Intel
Pentium
4 Processor in
478-Pin Package and Intel
845G/845GL/845GV Chipset Platform Design
Guide
for routing recommendations. This signal is used to provide noise
immunity.
REFSET
I
Analog
Resistor Set:
Set point resistor for the internal color palette DAC. A 137
,
1%
resistor is required between REFSET and GND.
DDCA_CLK
I/O
3.3 V
GPIO
Analog DDC Clock:
Clock signal for the I
2
C style interface that connects to
Analog CRT Display.
NOTE:
This signal may need to be level shifted to 5 V.
DDCA_DATA
I/O
3.3 V
GPIO
Analog DDC Data:
Data signal for the I
2
C style interface that connects to
Analog CRT Display.
NOTE:
This signal may need to be level shifted to 5 V.