W255

..........................Document #: 38-07255 Rev. *D Page 2 of 9

Pin Summary

Pin Name

Pins

Pin Description

SEL_DDR

48

Input to configure for DDR-ONLY mode or STANDARD SDRAM

mode.

1 = DDR-ONLY mode.

0 = STANDARD SDRAM mode.

When SEL_DDR is pulled HIGH or configured for DDR-ONLY mode, pin

4, 5, 6, 7, 10, 11,15, 16, 19, 20, 21, 22, 27, 28, 29, 30, 33, 34, 38, 39,

42, 43, 44 and 45 will be configured as DDR outputs.

Connect VDD3.3_2.5 to a 2.5V power supply in DDR-ONLY mode.

When SEL_DDR is pulled LOW or configured for STANDARD SDRAM

output, pin 4, 5, 6, 7, 10, 11, 15, 16, 19 and 20, 21, 22 will be configured

as STANDARD SDRAM outputs.Pin 27, 28, 29, 30, 33, 34, 38, 39, 42,

43, 44 and 45 will be configured as DDR outputs.

Connect VDD3.3_2.5 to a 3.3V power supply in STANDARD SDRAM

mode.

SCLK

25

SMBus clock input

SDATA

24

SMBus data input

BUF_IN

13

Reference input from chipset. 2.5V input for DDR-ONLY mode; 3.3V

input for STANDARD SDRAM mode.

FBOUT

1

Feedback clock for chipset. Output voltage depends on VDD3.3_2.5V.

PWR_DWN#

36

Active LOW input to enable power-down mode; all outputs will be

pulled LOW.

DDR[6:11]T

28, 30, 34, 39, 43, 45

Clock outputs. These outputs provide copies of BUF_IN.

DDR[6:11]C

27, 29, 33, 38, 42, 44

Clock outputs. These outputs provide complementary copies of

BUF_IN.

DDR[0:5]T_SDRAM

[10,0,2,4,6,8]

4, 6, 10, 15, 19, 21

Clock outputs. These outputs provide copies of BUF_IN. Voltage swing

depends on VDD3.3_2.5 power supply.

DDR[0:5]C_SDRAM

[11,1,3,5,7,9]

5, 7, 11, 16, 20, 22

Clock outputs. These outputs provide complementary copies of

BUF_IN when SEL_DDR is active. These outputs provide copies of

BUF_IN when SEL_DDR is inactive. Voltage swing depends on

VDD3.3_2.5 power supply.

VDD3.3_2.5

2, 8, 12, 17, 23

Connect to 2.5V power supply when W255 is configured for

DDR-ONLY mode. Connect to 3.3V power supply, when W255 is

configured for standard SDRAM mode.

VDD2.5

32, 37, 41, 47

2.5V voltage supply

GND

3, 9, 14, 18, 26, 31, 35, 40, 46 Ground