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Table 29 SPI BIOS Flash Interface Signal Descriptions
Signal Pin # Description I/O PU/PD Comment
SPI_CS# B97 Chip select for Carrier Board SPI BIOS Flash O 3.3 VSB Carrier shall pull to SPI_POWER when
external SPI is provided but not used
SPI_MISO
1
A92 Data in to module from carrier board SPI BIOS flash I 3.3 VSB
SPI_MOSI
1
A95 Data out from module to carrier board SPI BIOS flash O 3.3 VSB PU 4K75
3.3 VSB
SPI_MOSI is a bootstrap signal (see note
below)
SPI_CLK A94 Clock from module to carrier board SPI BIOS flash O 3.3 VSB
SPI_POWER A91 Power source for carrier board SPI BIOS flash. SPI_POWER shall be used to power
SPI BIOS flash on the carrier only
3.3 VSB
BIOS_DIS0# A34 Selection strap to determine the BIOS boot device I 3.3 VSB PU 10 KΩ
3.3 VSB
Carrier shall be left as no-connect
BIOS_DIS1# B88 Selection strap to determine the BIOS boot device. Refer to table 4.13 of the COM
Express Module Base Specification 3.0 for strapping options of BIOS disable signals
I 3.3 VSB PU 10 KΩ
3.3 VSB
Carrier shall be left as no-connect
Note
1.
These signals have special functionality during the reset process. They may bootstrap some basic important functions of the module. For
more information refer to section 8.2 “Bootstrap Signals”.
Table 30 Miscellaneous Signal Descriptions
Signal Pin # Description I/O PU/PD Comment
I2C_CK B33 General purpose I²C port clock output/input I/O 3.3 V PU 2K2 3.3 VSB
I2C_DAT B34 General purpose I²C port data I/O line I/O 3.3 V PU 2K2 3.3 VSB
SPKR
1
B32 Output for audio enunciator, the “speaker” in PC-AT systems O 3.3 V Bootstrap signal (see note below)
WDT B27 Output indicating that a watchdog time-out event has occurred O 3.3 V PD 100 KΩ
FAN_PWMOUT
2
B101 Fan speed control. Uses the Pulse Width Modulation (PWM) technique to control
the fan’s RPM
O OD
3.3 V
FAN_TACHIN
2
B102 Fan tachometer input I OD PU 47K5 3.3 V Requires a fan with a two pulse output
TPM_PP A96 Physical Presence pin of Trusted Platform Module (TPM). Active high. TPM chip has
an internal pull-down. This signal is used to indicate Physical Presence to the TPM
I 3.3 V PD 1 KΩ
Note
1.
This signal has special functionality during the reset process. It may bootstrap some basic important functions of the module. For more
information refer to section 8.2 “Bootstrap Signals”.
2.
Pins are protected on the module by a series schotty diode. Therefore, pull-down resistor is required on the carrier board for proper logic
level.
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