CY2254A

Rev 1.0, November 25, 2006

Page 2 of 7

Pin Summary

Name

1

2

Description

1

1

Voltage supply

2

2

Reference crystal input

3

3

Reference crystal feedback

4

4

Ground

OE

5

5

CPUCLK0

6

6

CPU clock output

CPUCLK1

7

7

CPU clock output

8

8

Voltage supply

CPUCLK2

9

9

CPU clock output

CPUCLK3

10

10

CPU clock output

11

11

Ground

S1

12

12

S0

13

13

14

14

Voltage supply

PCICLK0

15

15

PCI clock output

PCICLK1

16

16

PCI clock output

17

17

Ground

PCICLK5

18

18

PCI clock output

PCICLK4

19

19

PCI clock output

20

20

Voltage supply

PCICLK3

21

21

PCI clock output

PCICLK2

22

22

PCI clock output

23

23

Ground

IOCLK

24

24

I/O clock output (24 MHz)

KBDCLK

25

Keyboard controller clock output (12 MHz)

USBCLK

25

Universal Serial Bus clock output (48 MHz)

26

26

Voltage supply

REF1

27

27

Reference clock output (14.318 MHz)

REF0

28

28

Reference clock output (14.318 MHz)

Function Table

Option

OE

S0

S1

XTALIN

CPUCLK

PCICLK

Ref. Clock

Output

IOCLK

KBDCLK

1 only

USBCLK

2 only

1, 2

0

X

X

14.318 MHz High-Z

High-Z

High-Z

High-Z

High-Z

High-Z

1, 2

1

0

0

14.318 MHz 50.0 MHz

25.0 MHz

14.318 MHz 24 MHz

12 MHz

48 MHz

1, 2

1

0

1

14.318 MHz 60.0 MHz

30.0 MHz

14.318 MHz 24 MHz

12 MHz

48 MHz

1, 2

1

1

0

14.318 MHz 66.66 MHz

33.33 MHz

14.318 MHz 24 MHz

12 MHz

48 MHz

1

1

1

1

TCLK/2

TCLK/4

TCLK

TCLK/4

TCLK/8

2

1

1

1

14.318 MHz 55.0 MHz

27.5 MHz

14.318 MHz 24 MHz

48 MHz

Note:

2. TCLK is a test clock on XTALIN (pin 2) during test mode.