VT82C686B
Revision 1.71 June 9, 2000
-26-
Pinouts
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Resets and Clocks
Signal Name
Pin #
I/O
Signal Description
PWRGD
W6
I
Power Good. Connected to the PWRGOOD signal on the Power Supply.
PCIRST#
B16
O
PCI Reset. Active low reset signal for the PCI bus. The VT82C686B will
assert this pin during power-up or from the control register.
RSTDRV
J1
O
Reset Drive. Reset signal to the ISA bus. Connect through an inverter to the
chipset north bridge RESET# input and to PCI bus RESET#.
BCLK
H5
O
Bus Clock. ISA bus clock.
OSC
E4
I
Oscillator. 14.31818 MHz clock signal used by the internal Timer.
RTCX1
Y5
I
RTC Crystal Input: 32.768 KHz crystal or oscillator input. This input is
used for the internal RTC and for power-well power management logic.
RTCX2
W5
O
RTC Crystal Output: 32.768 KHz crystal output
SLOWCLK / GPO0
T8
O
Slow Clock. .Frequency selectable if PMU function 4 Rx54[1-0] is nonzero
(set to 01, 10, or 11).
Power and Ground
Signal Name
Pin #
I/O
Signal Description
VCC
F7, F10, F12-F14,
H6, H15, J6, J15,
K6, K15, M6,
M15, N6, N15,
R7-R8, R11, R14
P
Core Power. 3.3V nominal (3.15V to 3.45V). This supply is turned on only
when the mechanical switch on the power supply is turned on and the
PWRON signal is conditioned high. This pin should be connected to the
same voltage as the CPU I/O circuitry.
Internally connected to hardware
monitoring system voltage detection circuitry for 3.3V monitoring.
GND
F6, F11, F15, G6,
G15, J9-J12, K9-
K12, L6, L9-L12,
L15, M9-M12,
P6, P15, R6, R15
P
Ground. Connect to primary motherboard ground plane.
VCCS
R9-R10
P
Suspend Power. Always available unless the mechanical switch of the power
supply is turned off. If the “soft-off” state is not implemented, then this pin
can be connected to VCC. Signals powered by or referenced to this plane are:
PWRGD, RSMRST#, PWRBTN#, SMBCLK, SMBDATA, SUSCLK,
SUSA# / GPO1, SUSB# / GPO2, SUSC#, SUSST1# / GPO6, GPI1 / IRQ8#,
GPI2 / BATLOW#, GPI3 / LID, GPI5 / PME#, GPI6 / SMBALRT#, GPI7 /
RING#, GPO0
VBAT
Y6
P
RTC Battery. Battery input for internal RTC (RTCX1, RTCX2)
VREF
T13
P
Voltage Reference (5V
±5%). For thermal sensing and 5V input tolerance.
VCCH
R12
P
Hardware Monitor Power.
Power for hardware monitoring subsystem
(voltage monitoring, temperature monitoring, and fan speed monitoring).
Connect to VCC through a ferrite bead.
GNDH
R13
P
Hardware Monitor Ground. Connect to GND through a ferrite bead.
VCCU
F9
P
USB Differential Output Power.
Power for USB differential outputs
(USBP0+, P0-, P1+, P1-, P2+, P2-, P3+, P3-). Connect to VCC through a
ferrite bead.
GNDU
F8
P
USB Differential Output Ground. Connect to GND through a ferrite bead.
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