W137
Pin Definitions
Pin Name
CPU0:1
Pin No.
24, 23
Pin
Type
O
Pin Description
CPU Clock Outputs 0 and 1. These two CPU clock outputs are controlled by the
CPU_STOP# control pin. Output voltage swing is controlled by voltage applied to
VDDQ2. Frequency is selected per
Table 1.
PCI Bus Clock Outputs 1 through 5. These five PCI clock outputs are controlled by
the PCI_STOP# control pin. Output voltage swing is controlled by voltage applied to
VDDQ3. Frequency is selected per
Table 1.
Fixed PCI Clock Output. Unlike PCI1:5 outputs, this output is not controlled by the
PCI_STOP# control pin; it cannot be forced LOW by PCI_STOP#. Output voltage
swing is controlled by voltage applied to VDDQ3. Frequency is selected per
Table 1.
CPU_STOP# Input. When brought LOW, clock outputs CPU0:1 are stopped LOW
after completing a full clock cycle (2–3 CPU clock latency). When brought HIGH,
clock outputs CPU0:1 start with a full clock cycle (2–3 CPU clock latency).
PCI_STOP# Input. The PCI_STOP# input enables the PCI1:5 outputs when HIGH
and causes them to remain at logic 0 when LOW. The PCI_STOP# signal is latched
on the rising edge of PCI_F. Its effect takes place on the next PCI_F clock cycle.
I/O Dual-Function REF0 and SEL48# Pin. Upon power-up, the state of SEL48# is
latched. The state is set by either a 10K resistor to GND or to V
DD
. A 10K resistor to
GND causes pin 14 to provide a 48-MHz clock. If the pin is strapped to V
DD
, pin 14
will provide a 24-MHz clock. After 2 ms, the pin becomes a high-drive output that
produces a copy of 14.318 MHz.
I/O Dual-Function REF1 and SPREAD# Pin. Upon power-up, the state of SPREAD#
is latched. The state is set by either a 10K resistor to GND or to V
DD
. A 10K resistor
to GND enables Spread Spectrum function. If the pin is strapped to V
DD
, Spread
Spectrum is disabled. After 2 ms, the pin becomes a high-drive output that produces
a copy of 14.318 MHz.
I/O
Dual-Function 24 MHz or 48 MHz Output and Output Enable Input. Upon
power-up, the state of pin 14 is latched. The state is set by either a 10K resistor to
GND or to V
DD
. A 10K resistor to GND latches OE LOW, and all outputs are tri-stated.
If the pin is strapped to V
DD
, OE is latched HIGH and all outputs are active. After 2
ms, the pin becomes an output whose frequency is set by the state of pin 27 on
power-up.
48 MHz Output. Fixed 48 MHz USB output. Output voltage swing is controlled by
voltage applied to VDDQ3.
Frequency Selection Input. Select power-up default CPU clock frequency as shown
in
Table 1.
Crystal Connection or External Reference Frequency Input. This pin can either be
used as a connection to a crystal or to a reference signal.
Crystal Connection. An input connection for an external 14.318 MHz crystal. If using
an external reference, this pin must be left unconnected.
Power Down Control. When this input is LOW, device goes into a low-power standby
condition. All outputs are held LOW. CPU and PCI clock outputs are stopped LOW
after completing a full clock cycle (2–3 CPU clock cycle latency). When brought
HIGH, CPU and PCI outputs start with a full clock cycle at full operating frequency
(3 ms maximum latency).
Power Connection. Connected to 3.3V.
Power Connection. Power supply for CPU0:1 output buffers. Connected to 2.5V.
Ground Connection. Connect all ground pins to the common system ground plane.
PCI1:5
5, 6, 9, 10, 11
O
PCI_F
4
O
CPU_STOP#
18
I
PCI_STOP#
20
I
REF0/SEL48#
27
I/O
REF1/SPREAD#
26
I/O
24/48MHz/OE
14
I/O
48MHz
SEL100/66#
X1
X2
PWR_DWN#
13
16
2
3
17
O
I
I
I
I
VDDQ3
VDDQ2
GND
8, 12, 19, 28
25
1, 7, 15, 21, 22
P
P
G
Rev 1.0, November 24, 2006
Page 2 of 8
SPECTRALINEAR [ SPECTRALINEAR INC ]
