W196
PRELIMINARY
Document #: 38-07170 Rev. *A
Page 2 of 12
Pin Definitions
Pin Name
Pin
No.
Pin
Type
Pin Description
CPU0:1
22, 21
O
CPU Clock Outputs 0 through 1: These two CPU clocks run at a frequency set by
FS0:1 or the serial data interface. See Table 1 and Table 5. Output voltage swing is
set by the voltage applied to VDDQ2.
PCI1:6
PCI_F
5, 6, 7, 8, 10,
11, 4
O
PCI Bus Clock Outputs 1 through 6 and PCI_F: These seven PCI clock outputs
run synchronously to the CPU clock. Voltage swing is set by the power connection
to VDDQ3.
IOAPIC
24
O
I/O APIC Clock Output: Provides 14.318-MHz fixed frequency. The output voltage
swing is set by the power connection to VDDQ2.
48MHz
13
O
48-MHz Output: Fixed 48-MHz USB clock. Output voltage swing is controlled by
voltage applied to VDDQ3.
24_48MHz/FS1
14
I/O
24-MHz or 48-MHz Output/Frequency Select 1 Input: Frequency is set by the state
of pin 27 on power-up. This pin doubles as the select strap to determine device
operating frequency as described in Table 1.
REF2X/SEL48#
27
I/O
I/O Dual-Function REF2X and SEL48# Pin: Upon power-up, the state of SEL48#
is latched. The initial state is set by either a 10K resistor to GND or to VDD. A 10K
resistor to GND causes pin 14 to output 48 MHz. If the pin is strapped to VDD, pin
14 will output 2 4MHz. After 2 ms, the pin becomes a high-drive output that produces
a copy of 14.318 MHz.
FS0
16
I
Frequency Selection 0 Input: Selects CPU clock frequency as shown in Table 1
on page 1.
SDATA
18
I/O
I2C Data Pin: Data should be presented to this input as described in the I2C section
of this data sheet. Internal 250-k
Ω pull-up resistor.
SCLOCK
17
I
I2C Clock Pin: The I2C Data clock should be presented to this input as described in
the I2C section of this data sheet.
X1
1
I
Crystal Connection or External Reference Frequency Input: Connect to either
a 14.318-MHz crystal or other reference signal.
X2
2
I
Crystal Connection: An input connection for an external 14.318-MHz crystal. If
using an external reference, this pin must be left unconnected.
VDDQ3
9, 12, 20, 26
P
Power Connection: Power supply for core logic and PLL circuitry, PCI, 48/24MHz,
and Reference output buffers. Connect to 3.3V supply.
VDDQ2
23, 25
P
Power Connection: Power supply for IOAPIC and CPU output buffers. Connect to
2.5V supply.
GND
3, 15, 19, 28
G
Ground Connections: Connect all ground pins to the common system ground
plane.
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