CY28409
Document #: 38-07445 Rev. *D
Page 2 of 17
Pin Description
Pin No.
Name
Type
Description
1, 2
REF(0:1)
O, SE Reference Clock. 3.3V 14.318-MHz clock output.
4XIN
I
Crystal Connection or External Reference Frequency Input. This pin has dual
functions. It can be used as an external 14.318-MHz crystal connection or as an external
reference frequency input.
5
XOUT
O, SE Crystal Connection. Connection for an external 14.318-MHz crystal output.
41,44,47
CPUT(0:2)
O, DIF CPU Clock Output. Differential CPU clock outputs. See Table 1 for frequency config-
uration.
40,43,46
CPUC(0:2)
O, DIF CPU Clock Output. Differential CPU clock outputs. See Table 1 for frequency config-
uration.
38, 37
SRCT, SRCC
O, DIF Differential serial reference clock.
22,23,26,27
3V66(0:3)
O, SE 66-MHz Clock Output. 3.3V 66-MHz clock from internal VCO.
29
3V66_4VCH
O, SE 48-/66-MHz Clock Output. 3.3V selectable through SMBus to be 66 or 48 MHz.
7,8,9
PCIF(0:2)
O, SE Free-running PCI Output. 33-MHz clocks divided down from 3V66.
12,13,14,
15,18,19,20
PCI(0:6)
O, SE PCI Clock Output. 33-MHz clocks divided down from 3V66.
31,
USB_48
O, SE Fixed 48-MHz clock output.
32
DOT_48
O, SE Fixed 48-MHz clock output.
51,56
FS_A, FS_B
I
3.3V LVTTL input for CPU frequency selection.
52
IREF
I
Current Reference. A precision resistor is attached to this pin which is connected to
the internal current reference.
21
PD#
I, PU
3.3V LVTTL input for Power-Down# active LOW.
50
CPU_STP#
I, PU
3.3V LVTTL input for CPU_STP# active LOW.
49
PCI_STP#
I, PU
3.3V LVTTL input for PCI_STP# active LOW.
35
VTT_PWRGD#
I
3.3V LVTTL input is a level sensitive strobe used to latch the FS_A and FS_B
inputs (active LOW).
30
SDATA
I/O
SMBus-compatible SDATA.
28
SCLK
I
SMBus-compatible SCLOCK.
53
VSS_IREF
GND
Ground for current reference.
55
VDD_A
PWR
3.3V power supply for PLL.
54
VSS_A
GND
Ground for PLL.
42,48
VDD_CPU
PWR
3.3V power supply for outputs.
45
VSS_CPU
GND
Ground for outputs.
36
VDD_SRC
PWR
3.3V power supply for outputs.
39
VSS_SRC
GND
Ground for outputs.
34
VDD_48
PWR
3.3V power supply for outputs.
33
VSS_48
GND
Ground for outputs.
10,16
VDD_PCI
PWR
3.3V power supply for outputs.
11,17
VSS_PCI
GND
Ground for outputs.
24
VDD_3V66
PWR
3.3V power supply for outputs.
25
VSS_3V66
GND
Ground for outputs.
3
VDD_REF
PWR
3.3V power supply for outputs.
6
VSS_REF
GND
Ground for outputs.