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9.2
Bootstrap Signals
Table 37 Bootstrap Signal Descriptions
Signal
Pin # Description of Bootstrap Signal
I/O
PU/PD
Comment
HDA_SDOUT
A33
High Definition Audio Serial Data Output
O 3.3 VSB
PU 1 kΩ 3.3 VSB
SPKR
B32
Output for audio enunciator, the “speaker” in PC-AT systems
O 3.3 V
PEG_LAN_RV#
D54
PCI Express Graphics lane reversal input strap. Pull low on the carrier
board to reverse lane order
I 3.3 V
PU 10 kΩ 3.3 V
ESPI_EN#
B47
Used by the carrier to indicate the operating mode of the LPC/eSPI bus I
PU 20 kΩ 3.3 VSB
SPI_MISO
A92
Data in to module from carrier board SPI BIOS flash
I 3.3 VSB
SPI_MOSI
A95
Data out from module to carrier board SPI BIOS flash
O 3.3 VSB
BIOS_DIS0#
A34
Selection strap to determine the BIOS boot device
I 3.3 VSB
PU 10 kΩ 3.3 VSB
BIOS_DIS1#
B88
Selection strap to determine the BIOS boot device
I 3.3 VSB
PU 10 kΩ 3.3 VSB
DDI1_CTRLDATA_AUX-
D16
Multiplexed with DP1_AUX- and HDMI1_CTRLDATA
PU 100 kΩ 3.3 V
DP1_AUX-
DP AUX- function if DDI1_DDC_AUX_SEL is no connect
I/O PCIE
HDMI1_CTRLDATA
HDMI/DVI I2C CTRLDATA if DDI1_DDC_AUX_SEL is pulled high
I/O OD 3.3 V
DDI2_CTRLDATA_AUX-
C33
Multiplexed with DP2_AUX- and HDMI2_CTRLDATA
PU 100 kΩ 3.3 V
DP2_AUX-
DP AUX- function if DDI2_DDC_AUX_SEL is no connect
I/O PCIE
HDMI2_CTRLDATA
HDMI/DVI I2C CTRLDATA if DDI2_DDC_AUX_SEL is pulled high
I/O OD 3.3 V
DDI3_CTRLDATA_AUX-
C37
Multiplexed with DP3_AUX- and HDMI3_CTRLDATA
PU 100 kΩ 3.3 V
DP3_AUX-
DP AUX- function if DDI3_DDC_AUX_SEL is no connect
I/O PCIE
HDMI3_CTRLDATA
HDMI/DVI I2C CTRLDATA if DDI3_DDC_AUX_SEL is pulled high
I/O OD 3.3 V
Caution
1. The signals listed in the table above are used as chipset configuration straps during system reset. In this condition (during reset), they are
inputs that are pulled to the correct state by either COM Express™ internally implemented resistors or chipset internally implemented
resistors that are located on the module.
2. No external DC loads or external pull-up or pull-down resistors should change the configuration of the signals listed in the above table.
External resistors may override the internal strap states and cause the COM Express™ module to malfunction and/or cause irreparable
damage to the module.