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5 Hardware extensions
Copyright © COM Express™ Extension
Specification Rev 013
17
5.2.1 Alternative GPIO use for SDIO Interface
Pin GPIO SDIO Pin GPIO SDIO
A54
GPI0 DATA0
B54
GPO1
CMD
A63
GPI1 DATA1
B57
GPO2
WP
A67
GPI2 DATA2
B63
GPO3
CD#
A85
GPI3 DATA3
A93
GPO0
CLK
SDIO Pin description
Signal Type Description
SD_DATA[3:0] I/O
CMOS3.3
SDIO Controller 0/1/2 Data: These signals operate
in push-pull mode. The SD card includes internal pull-
up resistors for all data lines. By default, after power-
up, only SDn_DATA0 is used for data transfer. Wider
data bus widths can be configured for data transfer.
SD_CMD I/O
CMOS3.3
SDIO Controller 0/1/2 Command: This signal is
used for card initialization and transfer of commands.
It has two operating modes: open-drain for
initialization mode, and push-pull for fast command
transfer.
SD1_CLK O
CMOS3.3
SDIO Controller 0/1/2 Clock: With each cycle of this
signal a one-bit ransfer on the command and each
data line occurs.
This signal is generated by Intel SCH at a maximum
frequency of:
24 Mhz for SD and SDIO.
48 Mhz for MMC.
SD0_WP I
CMOS3.3
SDIO Controller 0/1/2 Write Protect: These signals
denote the state of the write-protect tab on SD cards.
SD1_CD# I
CMOS3.3
SDIO Controller 0/1/2 Card Detect: Indicates when
a card is present in an external slot.