Compaq COM Express Extension User Manual

Page 17

5 Hardware extensions

Specification Rev 013

5.2.1

Alternative GPIO use for SDIO Interface

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.