82845G Datasheet, PDF (36/193 Pages) Intel Corporation – Intel 82845G/82845GL/82845GV Graphics and Memory Controller Hub (GMCH)

Signal Description
2.7
2.8
36
Clocks, Reset, and Miscellaneous Signals
Signal Name
HCLKP
HCLKN
GCLKIN
DREFCLK
RSTIN#
PWROK
TESTIN#
Type
I
CMOS
I
LVTTL
I
LVTTL
I
LVTTL
I
3.3 V
GPIO
I
1.5 V
CMOS
Description
Differential Host Clock In: These pins receive a low voltage differential host clock
from the external clock synthesizer.
66 MHz Clock In: This pin receives a 66 MHz clock from the clock synthesizer.
This clock is used by AGP and hub interface clock domains.
Display Clock Input: This pin provides a 48 MHz input clock to the Display PLL
that is used for 2D/Video/Flat Panel and DAC.
Reset In: When asserted, this signal asynchronously resets the GMCH logic. This
signal is connected to the PCIRST# output of the Intel^® ICH4. All AGP/PCI output
and bi-directional signals will also tri-state compliant to PCI Local Bus
Specification, Revision 2.0 and PCI Local Bus Specification, Revision 2.1.
Power OK: When asserted, PWROK is an indication to the GMCH that the core
power and GCLKIN have been stable for at least 10 µs.
Test Input: This pin is used for manufacturing and board lever test purposes.
RCOMP, VREF, VSWING Signals
Signal Name
HDVREF_[2:0]
HA_VREF
HCC_VREF
HX_RCOMP
HY_RCOMP
HX_SWING
HY_SWING
SM_VREF
SMXRCOMP
SMYRCOMP
AGP_VREF
AGP_RCOMP
HI_VREF
HI_RCOMP
HI_SWING
Type
I
I
I
I/O
CMOS
I
I
I/O
CMOS
I
I/O
CMOS
I
I/O
CMOS
I
Description
Host Data Reference Voltage: Reference voltage input for the data signals of the
Host AGTL+ interface.
Host Address Reference Voltage: Reference voltage input for the address
signals of the Host AGTL+ interface.
Host Common Clock Reference Voltage: Reference voltage input for the
common clock signals of the Host AGTL+ interface.
Host RCOMP: These pins are used to calibrate the Host AGTL+ I/O buffers.
Host Voltage Swing: These pins provide a reference voltage used by the PSB
RCOMP circuit. HX_SWING is used for the signals handled by HX_RCOMP, and
HY_SWING is used for the signals handled by HY_RCOMP.
Memory Reference Voltage: Reference voltage input for DQ, DQS &
SRCVEN_IN#.
Memory RCOMP: These pins are used to calibrate the memory I/O buffers.
AGP Reference: The reference voltage for the AGP/DVO I/O buffers is 0.75 V.
Compensation for AGP: This signal is used to calibrate the AGP/DVO buffers.
This signal should be connected to ground through a 40 Ω pull-down resistor.
HI Reference: Reference voltage input for the hub interface.
Compensation for HI: This signal is used to calibrate the hub interface I/O
buffers. This signal should be connected to 1.5 V through a 68.1 Ω 1% pull-up
resistor
HI Voltage Swing: This signal provides a reference voltage used by the
HI_RCOMP circuit.
Intel^® 82845G/82845GL/82845GV GMCH Datasheet