Specifications

Ref# 420826 Intel
®
Atom™ processor CE4100 37
Platform Design Guide
Intel Confidential
4.6 Straps
The following table lists all of the straps, grouped into two categories.
• Miscellaneous Straps:
The DDR_X8, I2C_LED and TRUST_BOOT straps both have a weak internal pull-down for a
default value of ‘0’, and require a 1.0~1.1-KΩ pull-up to obtain the non-default value of
‘1’.
• Expansion Bus Straps:
The EXP_ADDR[15:0] straps each have a weak internal pull-up for a default value of ‘1’,
and require a 4.7-KΩ pull-down resistor to obtain the non-default value of ‘0’;
The EXP_DB[0] strap has a weak internal pull-down for a default value of ‘0’, and
requires a 7.5-KΩ pull-up resistor to obtain the non-default value of ‘1’.
The pull-up and pull-down resistor values will vary depending upon the loading on the
expansion bus, so external pull-up and pull-down resistors may be required to obtain the
default values. If there is significant bus loading on these straps causing signal integrity
issues, buffers controlled by the reset logic may be required to isolate the straps for
proper expansion bus operation.
Strap Name Pin Name Description
Miscellaneous Straps
DDR_X8 (AW33) DDR_X8 Sets the DDR data width
0: DDR is configured for x16 parts, 2 per channel
1: DDR is configured for x8 parts, 4 per channel
I2C_LED (AV34) I2C_LED Enable the LED display on board
0: I2C_LED display disable
1: I2C_LED display enable
TRUST_BOOT (AU36) TRUST_BOOT This is only for debug of trusted boot. When the Trusted
Boot fuses are programmed, this strap will have no effect.
For parts without the Trusted Boot fuse being
programmed, pulling this strap high will allow for trusted
boot operation.
0: Normal Boot Operation
1: Trusted Boot Operation
Expansion Bus Straps
FSB_RATIO_SEL EXP_ADDR[3:0] Selects ratio between FSB clock and Core clock speed.
Minimum ratio is 1:6:
others: Reserved
1001: 1:12 Only supported ratio
FSB_OVERRIDE EXP_ADDR[5:4] Define FSB frequency: Part must be fused at same speed.
00: Reserved
01: Reserved
10: Reserved
11: 100MHz Only supported frequency