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4.17
SDIO
The SD card standard is a standard for removable memory storages designed and licensed by the SD Card Association
(http://sdcard.org). The card form factor, electrical interface, and protocol are all part of the SD Card specification. The
Intel® System Controller Hub US15W supports up to 3 SDIO interfaces. On nanoETXexpress-SP the first interface SDIO#0
(4-bit wide) is shared with the module GPIO signals. The integrated SDIO 1.1/MMC 4.1 controller in US15W only supports
byte-address mode for SDIO storage cards up to 2GB. Sector-addressing and SDHC is not supported.
» MMC 4.1 transfer rates can be up to 48MHz and bus widths of 1, 4 or 8 bits
» SDIO 1.1 supports transfer rates up to 24MHz and bus widths of 1 or 4 bits
The following table shows which GPIO-ports can be used for the SD-card interface:
General purpose Input/output
GPI0
GPI1
GPI2
GPI3
GPO0
GPO1
GPO2
GPO3
The SD_CMD line needs a pull-up resistor that can vary depending on the length of the
electrical paths (typical from 10kOhm to 100kOhm).
The maximum length for SDIO signals on the baseboard should be 80mm.
44
COMe-mSP1 / Features and Interfaces
SD card interface signals
SLOT0_DATA0
SLOT0_DATA1
SLOT0_DATA2
SLOT0_DATA3
SLOT0_CLK
SLOT0_CMD
SLOT0_WP
SLOT0_CD#
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