Editing SD card (section)

===SDIO cards===
{{more citations needed|section=yes|date=September 2023}}
[[File:SDIO Vector.svg|thumb|upright=0.65|Secure Digital Input Output (SDIO) mark]]
[[File:HP PhotoSmart SDIO Kamera (cropped).jpg|thumb|upright|Camera using the SDIO interface to connect to some HP [[iPAQ]] devices]]

A SDIO (Secure Digital Input Output) card is an extension of the SD specification to cover I/O functions. SDIO cards are only fully functional in host devices designed to support their input-output functions (typically PDAs like the [[Palm Treo]], but occasionally laptops or mobile phones).{{citation needed|date=September 2023}} These devices can use the SD slot to support [[GPS]] receivers, [[modem]]s, [[barcode reader]]s, [[FM radio]] tuners, TV tuners, [[RFID]] readers, [[digital camera]]s and interfaces to [[Wi-Fi]], [[Bluetooth]], [[Ethernet]] and [[IrDA]]. Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface.{{citation needed|date=September 2023}}

SDIO cards support most of the memory commands of SD cards. SDIO cards can be structured as eight logical cards, although currently, the typical way that an SDIO card uses this capability is to structure itself as one I/O card and one memory card.{{citation needed|date=September 2023}}

The SDIO and SD interfaces are mechanically and electrically identical. Host devices built for SDIO cards generally accept SD memory cards without I/O functions. However, the reverse is not true, because host devices need suitable drivers and applications to support the card's I/O functions. For example, an HP SDIO camera usually does not work with PDAs that do not list it as an accessory. Inserting an SDIO card into any SD slot causes no physical damage nor disruption to the host device, but users may be frustrated that the SDIO card does not function fully when inserted into a seemingly compatible slot. (USB and Bluetooth devices exhibit comparable compatibility issues, although to a lesser extent thanks to standardized [[Class driver|USB device classes]] and [[Bluetooth profiles]].){{citation needed|date=September 2023}}

The [[#SDIO|SDIO]] family comprises Low-Speed and Full-Speed cards. Both types of SDIO cards support [[Serial Peripheral Interface]] (SPI) and one-bit SD bus types. Low-Speed SDIO cards are allowed to also support the four-bit SD bus; Full-Speed SDIO cards are required to support the four-bit SD bus. To use an SDIO card as a "combo card" (for both memory and I/O), the host device must first select four-bit SD bus operation. Two other unique features of Low-Speed SDIO are a maximum clock rate of 400&nbsp;kHz for all communications, and the use of Pin 8 as "interrupt" to try to initiate dialogue with the host device.<ref name="SDIOspec">{{cite web |url=https://www.sdcard.org/developers/overview/sdio/sdio_spec/ |title=Simplified Version of SDIO CARD SPEC |publisher=SD Association |access-date=2011-12-09 |archive-date=2015-04-15 |archive-url=https://web.archive.org/web/20150415230526/https://www.sdcard.org/developers/overview/sdio/sdio_spec/ |url-status=dead}}</ref>