W256
Document #: 38-07256 Rev. *C
Page 2 of 9
Pin Summary
Name
Pins
Description
SEL_DDR
28
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, all the buffers
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, all
the buffers will be configured as STANDARD SDRAM outputs.
Connect VDD3.3_2.5 to a 3.3V power supply in STANDARD SDRAM mode.
SCLK
16
SMBus clock input.
SDATA
15
SMBus data input.
BUF_IN
10
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#
2
Active LOW input to enable Power Down mode; all outputs will be pulled LOW.
DDR[0:5]T_SDRAM
[0,2,4,6,8,10]
3, 7, 12, 19, 23, 27
Clock outputs. These outputs provide copies of BUF_IN. Voltage swing depends
on VDD3.3_2.5 power supply.
DDR[0:5]C_SDRAM
[1,3,5,7,9, 11]
4, 8, 13, 18, 22, 26
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
5, 9, 14, 21, 25
Connect to 2.5V power supply when W256 is configured for DDR-ONLY mode.
Connect to 3.3V power supply, when W256 is configured for standard SDRAM
mode.
GND
6, 11, 17, 20, 24
Ground.
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