CY28RS400
Document #: 38-07637 Rev. *B
Page 2 of 19
Pin Description
Pin No.
Name
Type
Description
47,46,43,42,
41,40
CPUT/C[2:0]
O, DIF Differential CPU clock output.
Intel Type-X buffer.
50
PCI0/409_410
I/O,
PD
33-MHz clock output/CPU Frequency table Select
Intel Type-5 buffer.
0 = 410 frequency select table
1 = 409 frequency select table.
This has an internal pull-down
37
IREF
I
A precision resistor attached to this pin is connected to the internal current reference.
54
REF0/ FSA
I/O, SE, 14.318MHz REF clock ouput/ CPU Frequency Select. Intel Type-5 buffer.
53
REF1/FSB
I/O, SE 14.318MHz REF clock ouput
/ CPU Frequency Select. Intel Type-5 buffer.
52
REF2
O, SE 14.318MHz REF clock ouput. Intel Type-5 buffer.
7
SCLK
I,PU
SMBus-compatible SCLOCK.This pin has an internal pullup, but is tri-stated in power-down.
8
SDATA
I/O, PU SMBus compatible SDATA.This pin has an internal pullup, but is tri-stated in power-down.
27, 28, 30, 29
SRCST/C[1:0]
O, DIF Differential Selectable Serial reference clock. Intel Type-X buffer. Includes overclock
support through SMBUS
12, 13, 16,
17, 18, 19,
22, 23, 24, 25
,34,33
SRCT/C[5:0]
O, DIF 100 MHz Differential Serial reference clock. Intel Type-X buffer.
10,11
CLKREQ#[0:1]
I, SE,
PD
Output Enable control for SRCT/C. Output enable control required by Minicard
specification. These pins have an internal pull-down.
0 = Selected SRC outputs are enabled, 1 = Selected SRC outputs are disabled
4
USB_48
O, SE 48-MHz clock output. Intel Type-3A buffer.
6
VTT_PWRGD#/PD
I
PD
3.3V LVTTL input. This pin is a level sensitive strobe used to latch the FS_A, FS_B,
FS_C and 409_410 inputs. After asserting VTT_PWRGD# (active low), this pin
becomes a realtime input for asserting power down (active high)
48
CPU_STP#
I, PU 3.3V LVTTL input. This pin is used to gate the CPU outputs. CPU outputs are turned
off two cycles after assertion of this pin
9
FSC
I
3.3V LVTTL input. CPU Clock Frequency Select
3
VDD_48
PWR 3.3V power supply for USB outputs
45
VDD_CPU
PWR 3.3V power supply for CPU outputs
51
VDD_PCI
PWR 3.3V power supply for PCI outputs
56
VDD_REF
PWR 3.3V power supply for REF outputs
14, 21
VDD_SRC
PWR 3.3V power supply for SRC outputs
35
VDD_SRC1
PWR 3.3V power supply for SRC outputs
32
VDD_SRCS
PWR 3.3V power supply for SRCS outputs
39
VDDA
PWR 3.3V Analog Power for PLLs
5
VSS_48
GND Ground for USB outputs
44
VSS_CPU
GND Ground for CPU outputs
49
VSS_PCI
GND Ground for PCI outputs
55
VSS_REF
GND Ground for REF outputs
15, 20, 26
VSS_SRC
GND Ground for SRC outputs
36
VSS_SRC1
GND Ground for SRC outputs
31
VSS_SRCS
GND Ground for SRCS outputs
38
VSSA
GND Analog Ground
1
XIN
I
14.318-MHz Crystal Input
2
XOUT
O
14.318-MHz Crystal Output
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