Datasheet

Signal Description
36 Intel
®
82845G/82845GL/82845GV GMCH Datasheet
2.7 Clocks, Reset, and Miscellaneous Signals
2.8 RCOMP, VREF, VSWING Signals
Signal Name Type Description
HCLKP
HCLKN
I
CMOS
Differential Host Clock In: These pins receive a low voltage differential host clock
from the external clock synthesizer.
GCLKIN
I
LVTTL
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.
DREFCLK
I
LVTTL
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.
RSTIN#
I
LVTTL
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.
PWROK
I
3.3 V
GPIO
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.
TESTIN#
I
1.5 V
CMOS
Test Input: This pin is used for manufacturing and board lever test purposes.
Signal Name Type Description
HDVREF_[2:0] I
Host Data Reference Voltage: Reference voltage input for the data signals of the
Host AGTL+ interface.
HA_VREF I
Host Address Reference Voltage: Reference voltage input for the address
signals of the Host AGTL+ interface.
HCC_VREF I
Host Common Clock Reference Voltage: Reference voltage input for the
common clock signals of the Host AGTL+ interface.
HX_RCOMP
HY_RCOMP
I/O
CMOS
Host RCOMP: These pins are used to calibrate the Host AGTL+ I/O buffers.
HX_SWING
HY_SWING
I
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.
SM_VREF I
Memory Reference Voltage: Reference voltage input for DQ, DQS &
SRCVEN_IN#.
SMXRCOMP
SMYRCOMP
I/O
CMOS
Memory RCOMP: These pins are used to calibrate the memory I/O buffers.
AGP_VREF I AGP Reference: The reference voltage for the AGP/DVO I/O buffers is 0.75 V.
AGP_RCOMP
I/O
CMOS
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_VREF I HI Reference: Reference voltage input for the hub interface.
HI_RCOMP
I/O
CMOS
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_SWING I
HI Voltage Swing: This signal provides a reference voltage used by the
HI_RCOMP circuit.