Secure Digital

Secure Digital (SD) is a non-volatile anamnesis agenda architecture developed by the SD Agenda Association (SDA) for use in carriageable devices. The SD technology is acclimated by added than 400 brands beyond dozens of artefact categories and added than 8,000 models.1

SD comprises several families of cards:2 the original, Standard-Capacity (SDSC) card, a High-Capacity (SDHC) agenda family, an eXtended-Capacity (SDXC) agenda family,3 and the SDIO4 ancestors with input/output functions rather than just abstracts storage.

SD aswell comprises three altered anatomy factors: the aboriginal size, the "mini" size, and the "micro" admeasurement (see illustration). Electrically acquiescent adaptors acquiesce the use of a abate agenda in a host accessory congenital to authority a beyond card. There are abounding combinations of anatomy factors and accessory families.

Host accessories that accede with newer versions of the blueprint accommodate astern affinity and acquire earlier SD cards, but earlier host accessories do not admit newer cards. The SDA uses several trademarked logos to accomplish acquiescence with its blueprint and assure users of compatibility.5 This commodity explains several factors that can anticipate the use of a newer SD card:

A newer agenda may action greater accommodation than the host accessory can handle.

A newer agenda may use a book arrangement the host accessory cannot navigate.

Use of an SDIO agenda requires the host accessory be advised for the input/output functions the agenda provides.

The alignment of the agenda was afflicted starting with the SDHC family.

Some vendors produced SDSC cards aloft 1 GB afore the SDA had connected a adjustment of accomplishing so.

Types of cards

It authentic electrically identical cards in abate sizes: miniSD and microSD (originally called TransFlash). Abate cards are accessible in beyond slots through use of a acquiescent adapter. By comparison, Reduced Admeasurement MultiMediaCards (RS-MMCs) are artlessly beneath MMCs and can be acclimated in MMC slots by use of a concrete extender.

It authentic higher-capacity cards, some with faster speeds and added capabilities: SDHC (Secure Agenda High Capacity) and SDXC (Secure Agenda eXtended Capacity). These cards redefine the interface so that they cannot be acclimated in earlier host devices.

It authentic an SDIO agenda ancestors that provides input-output functions and may aswell accommodate anamnesis functions. These cards are alone absolutely anatomic in host accessories advised to abutment their input-output functions.

edit Concrete size

Size allegory of families: SD, miniSD, microSD

The SD agenda blueprint defines three concrete sizes. The SD and SDHC families are accessible in all three sizes, but the SDXC ancestors is not accessible in the mini size, and the SDIO ancestors is not accessible in the micro size.

Standard size

SD (SDSC), SDHC, SDXC, SDIO

32 mm × 24 mm × 2.1 mm

32 mm × 24 mm × 1.4 mm (as attenuate as MMC) for Attenuate SD (rare)

Mini size

miniSD, miniSDHC, miniSDIO

21.5 mm × 20 mm × 1.4 mm

Micro size

The microSD anatomy agency is the aboriginal anamnesis agenda architecture currently available.citation needed

microSD, microSDHC, microSDXC

15 mm × 11 mm × 1.0 mm

edit SDHC

16GB SDHC Class 6

The Secure Agenda High Accommodation (SDHC) format, authentic in Version 2.0 of the SD specification, supports cards with capacities up to 32 GB.1 The SDHC brand is accountant to ensure compatibility.6

SDHC cards are physically and electrically identical to standard-capacity SD cards (SDSC). The aloft affinity issues amid SDHC and SDSC cards are the redefinition of the Card-Specific Data (CSD) annals in Version 2.0 (see below), and the actuality that SDHC cards are alien preformatted with the FAT32 book system.

Host accessories that acquire SDHC cards are appropriate to acquire SDSC cards.1 However, host accessories advised for SDSC do not admit SDHC or SDXC anamnesis cards, although some accessories can do so through a firmware upgrade.7 Earlier operating systems crave patches to abutment SDHC. For instance, Microsoft Windows XP afore SP3 requires a application to abutment admission to SDHC cards.8 Windows Vista SP1 aswell requires a after account pack.910

edit SDXC

The Secure Agenda Extended Accommodation (SDXC) architecture supports cards up to 2 TB (2048 GB), compared to a absolute of 32 GB for SDHC cards in the SD 2.0 specification.

History

SDXC was appear at Customer Electronics Appearance (CES) 2009 (January 7–10, 2009). At the aforementioned show, SanDisk and Sony aswell appear a commensurable Anamnesis Stick XC another with the aforementioned 2 TB best as SDXC,11 and Panasonic appear affairs to aftermath 64 GB SDXC cards.12

On March 6, 2009, Pretec alien the aboriginal SDXC card,13 a 32 GB agenda with a read/write acceleration of 400 Mbit/s. But it was not until aboriginal 2010 that accordant host accessories came assimilate the market, including Sony's Handycam HDR-CX55V camcorder, Canon's EOS Rebel T2i Agenda SLR camera,14 a USB agenda clairvoyant from Panasonic, and an chip SDXC agenda clairvoyant from JMicron.15 The ancient laptops to accommodate SDXC agenda readers relied on a USB 2.0 bus, which does not acquire the bandwidth to abutment SDXC at abounding speed.16

Also in aboriginal 2010, bartering SDXC cards appeared from Toshiba (64 GB),1718 Panasonic (64 GB and 48 GB),19 and SanDisk (64 GB).20 In aboriginal 2011, Centon Electronics, Inc. (64 GB and 128 GB) and Lexar (128 GB)21 began shipment SDXC cards rated at Acceleration Class 10. Pretec offered cards from 8 GB to 128 GB rated at Acceleration Class 16.22

In September 2011, SanDisk appear a 64 GB microSDXC card.23 Kingmax appear a commensurable artefact in 2011.24

Compatibility with SDHC

SDXC host accessories acquire all antecedent families of SD anamnesis cards.25 Conversely, SDHC host accessories will acquire SDXC cards that chase Version 3.0, back the interface is identical,3 but the afterward issues may affect usability:

SDXC cards are pre-formatted with Microsoft's proprietary and patented exFAT book system, which the host accent ability not support. Back Microsoft does not broadcast the blueprint of exFAT and its use requires a non-free license, abounding another or earlier operating systems do not abutment exFAT for abstruse or acknowledged reasons. The use of exFAT on some SDXC cards may cede SDXC clashing as a accepted barter medium, as an SDXC agenda that uses exFAT would not be accessible in all host devices. Back the FAT32 book arrangement supports volumes up to the SDXC's best abstract accommodation of 2 TB as well, a user could reformat an SDXC agenda to use FAT32 for greater portability amid computers (see below), but customer articles such as agenda cameras and camcorders do not commonly accommodate the best to architecture SDXC cards as FAT32 nor do they acquire FAT32-reformatted SDXC cards.

An SDHC host accent will not analysis the new adequacy $.25 authentic for SDXC cards. It will accordingly not be able to use the new appearance of SDXC, such as alteration speeds aloft UHS104.26

Host Operating Arrangement support

Microsoft Windows versions that abutment SDXC are: Windows 7, Windows Vista SP1+,3 Windows XP SP2 or SP3 with KB955704,27 Windows Server 2008 SP1+, Windows Server 2003 SP2 or SP3 with KB955704, and Windows CE 6.0 and higher.

Apple Mac OS X versions that abutment SDXC cards and exFAT are Mac OS X Snow Leopard 10.6.5 or after including OS X Lion 10.7.2829

BSD and Linux systems that abutment SDHC cards aswell abutment SDXC cards that accommodate a accordant book system, but they commonly do not abutment the proprietary exFAT book arrangement that is installed on SDXC cards, because of apparent issues. A bartering Linux disciplinarian is accessible for the exFAT book system.30 The user may reformat the agenda to accommodate a altered book arrangement (see below).

edit SDIO

Camera application the SDIO interface to affix to some HP iPAQ devices

A SDIO (Secure Agenda Input Output) agenda is an addendum of the SD blueprint to awning I/O functions. Host accessories that abutment SDIO (typically PDAs like the Palm Treo, but occasionally laptops or adaptable phones) can use the SD aperture to abutment GPS receivers, modems, barcode readers, FM radio tuners, TV tuners, RFID readers, agenda cameras, and interfaces to Wi-Fi, Bluetooth, Ethernet, and IrDA. Abounding added SDIO accessories acquire been proposed, but it is now added accepted for I/O accessories to affix application the USB interface.

SDIO cards abutment a lot of of the anamnesis commands of SD cards. SDIO cards can be structured as 8 analytic cards, although currently, the archetypal way that an SDIO agenda uses this adequacy is to anatomy itself as one I/O agenda and one anamnesis card.

Host abutment for SDIO

The SDIO and SD interfaces are mechanically and electrically identical. Host accessories congenital for SDIO cards about acquire SD anamnesis cards after I/O functions. However, the about-face is not true, because host accessories charge acceptable drivers and applications to abutment the card's I/O functions. For example, an HP SDIO camera usually does not plan with PDAs that do not account it as an accessory. Inserting an SDIO agenda into any SD aperture causes no concrete accident nor disruption to the host device, but users may be balked that the SDIO agenda does not action absolutely if amid into a acutely accordant slot. (Bluetooth accessories display commensurable affinity issues, although to a bottom admeasurement acknowledgment to connected Bluetooth profiles.)

Features

Card aegis (non-DRM)

Write protection

When searching at the agenda from the top, the appropriate ancillary (the ancillary with the askew corner) accept to be notched.

On the larboard side, there may be a write-protection notch. If the cleft is omitted, the agenda can be apprehend and written. If the agenda is notched, it is read-only, except that the cleft may be partly covered by a sliding tab. In this case, the user can accelerate the tab advancement (toward the contacts) to acknowledge the agenda read/write, or bottomward to acknowledge it read-only.

The attendance of a notch, and the attendance and position of a tab, accept no aftereffect on the SD card's operation. A host accessory that supports address aegis should debris to address to an SD agenda that is appointed read-only in this way. Some host accessories do not abutment address protection, which is an alternative affection of the SD specification. Host accessories that do obey a read-only adumbration may accord the user a way to override it. The miniSD and microSD formats do not abutment address aegis with the notch-and-tab method.

Typical cards awash as a average for adequate agreeable are assuredly apparent read-only by accepting a cleft and no sliding tab.

Card password

A host accessory can lock an SD agenda appliance a countersign of up to 16 bytes, about supplied by the user. A bound agenda interacts commonly with the host accessory except that it rejects commands to apprehend and address data. A bound agenda can be apart alone by accouterment the aforementioned password. The host accessory can, afterwards bartering the old password, specify a new countersign or attenuate locking. After the countersign (typically, in the case that the user forgets the password), the host accessory can command the agenda to abolish all the abstracts on the agenda for approaching re-use (except agenda abstracts beneath DRM), but there is no way to accretion admission to the absolute data.

edit DRM features

All SD cards absorb a agenda rights administration (DRM) scheme. Roughly 10% of the accumulator accommodation of an SD agenda is not attainable to the user, but is acclimated by the on-card processor to verify the character of an appliance affairs that it will afresh acquiesce to apprehend adequate content. The agenda prohibits added accesses, such as users aggravating to accomplish copies of adequate files.

The DRM arrangement anchored in the SD cards is the Agreeable Aegis for Recordable Media (CPRM or CPPM) blueprint of the 4C Entity, which actualization the Cryptomeria blank (also termed C2). The blueprint is kept abstruse and is attainable alone to licensees. The arrangement has not been torn or hacked, but this affection of SD cards is rarely acclimated to assure content. DVD-Audio uses the aforementioned DRM scheme.

Windows Media files can be DRM-encoded so as to accomplish use of the SD card's DRM abilities.citation needed

Windows Buzz 7 accessories use SD cards advised to be accessed alone by the buzz architect or adaptable provider. An SD agenda amid into the buzz beneath the array alcove becomes bound "to the buzz with an automatically generated key" so that "the SD agenda cannot be apprehend by addition phone, device, or PC".31 Symbian devices, however, are some of the actual few which can accomplish the all-important low-level architecture operations on bound SD cards. It is accordingly accessible to use a accessory such as the Nokia N8 to reformat the agenda for consecutive use in added devices.32

The Super Agenda cards bogus by Super*Talent are the aforementioned in actualization and action as Secure Agenda cards, but they abridgement the CPRM affection of Secure Agenda cards.33

edit Vendor enhancements

SD cards with dual-interface SD and USB connections

SanDisk cards in assorted colors

Vendors accept approved to differentiate their articles in the bazaar through assorted vendor-specific features:

Integrated Wi-Fi — Eye-Fi produces several SD cards with congenital Wi-Fi transceivers accouterment changeless aegis (WEP 40; 104; and 128, WPA-PSK, and WPA2-PSK). The agenda lets any agenda camera with an SD aperture address captured images over a wireless network, or abundance the images on the card's anamnesis until it is in ambit of a wireless network.34 Some models geotag their pictures.

Pre-loaded agreeable — In 2006, SanDisk appear Gruvi, a microSD agenda with added Agenda Rights Administration (DRM) features, with which to use anamnesis cards as a average to advertise content. SanDisk afresh appear pre-loaded cards in 2008, beneath the slotMusic name, this time not appliance any of the DRM capabilities of the SD card.35 In 2011, SanDisk offered assorted collections of 1000 songs on a individual slotMusic agenda for about $40,36 now belted to accordant accessories and after the adeptness to archetype the files.

Integrated USB adapter — The SanDisk SD Plus artefact can be acquainted anon into a USB anchorage after defective a USB agenda reader.37 Added companies alien commensurable products, such as the Duo SD artefact of OCZ Technology and the 3 Way (microSDHC, SDHC, and USB) artefact of A-DATA, which was attainable in 2008 only.

Different colors — SanDisk has acclimated assorted colors of artificial or adhering label, including a "gaming" band in clear-cut artificial colors that adumbrated the card's capacity.

Integrated affectation — In 2006, A-DATA appear a Super Info SD agenda with a agenda affectation that provided a two-character characterization and showed the bulk of bare anamnesis on the card.38

Speeds

An SD card's acceleration is abstinent by how bound advice can be apprehend from, or accounting to, the card. In applications that crave abiding address throughput, such as video recording, the accessory ability not accomplish abundantly if the SD card's chic appraisement avalanche beneath a accurate speed. For example, a camcorder congenital for a Chic 6 agenda may ache dropouts or besmirched video if a slower agenda is used. Digital cameras may acquaintance a apparent lag amid shots, while the camera writes the account to a slower card.

A card's acceleration depends on abounding factors, such as the following:

The likelihood of bendable errors that the card's ambassador have to re-try

The actuality that, on a lot of cards, autograph abstracts requires the ambassador to apprehend and abolish a beyond region, again carbon that absolute arena with the adapted allotment changed

The achievability of fragmentation: that a physique of advice the host angle as a assemblage is, for actual reasons, accounting to non-contiguous regions of memory. (This achievability does not could cause rotational or head-movement delays as with alluring media, but it does alter the bulk of ciphering the card's ambassador have to do.)

In aboriginal SD cards, the acceleration was abstinent with the × rating, which compared the boilerplate acceleration of account abstracts to that of the aboriginal CD-ROM drive. Currently, the official assemblage of altitude is the Acceleration Chic Rating, which guarantees a minimum amount at which abstracts can be accounting to the card.

The newer families of SD agenda advance agenda acceleration by accretion the bus amount (the abundance of the alarm arresting that strobes advice into and out of the card). Whatever the bus rate, the agenda can arresting to the host that it is "busy" until a apprehend or a address operation is complete. Compliance with a college acceleration appraisement is a agreement that the agenda banned its use of the "busy" indication.

edit Acceleration Chic Rating

32GB SDHC card

The Acceleration Chic Appraisement is the official assemblage of acceleration altitude for SD cards. The chic amount guarantees a minimum address acceleration as a assorted of 8 Mbit/s (1 MB/s). The SDA defines several acceleration chic ratings, but manufacturers may affirmation acclimation to those ratings after absolute verification.

The host accessory can apprehend a card's acceleration class, clashing the beforehand "×" acceleration ratings. A accessory can acquaint the user if the agenda letters a acceleration chic that avalanche beneath an application's minimum need.39

These are the ratings of all currently accessible cards:4041

Chic Speed

SDHC Acceleration Chic 2.svg Chic 2 2 MB/s

SDHC Acceleration Chic 4.svg Chic 4 4 MB/s

SDHC Acceleration Chic 6.svg Chic 6 6 MB/s

SDHC Acceleration Chic 10.svg Chic 10 10 MB/s

Speed Classes 2, 4, and 6 advance that the agenda supports the agnate amount of MB/s as a minimum abiding address acceleration for a agenda in a burst state. Chic 10 asserts that the agenda supports 10 MB/s as a minimum non-fragmented consecutive address speed.39 By comparison, the earlier "×" appraisement abstinent best acceleration beneath ideal conditions, and was ambiguous as to whether this was apprehend acceleration or address speed.

edit × rating

The × appraisement is a assorted of the accepted CD-ROM drive acceleration of 1.2 Mbit/s (approximately 150 kB/s). Basic cards alteration abstracts up to six times (6×) the CD-ROM speed; that is, 7.2 Mbit/s. The 2.0 blueprint defines speeds up to 200×, but is not as specific as Acceleration Classes are on how to admeasurement speed. Manufacturers may address best-case speeds and may address the card's fastest apprehend speed, which is about faster than the address speed. Vendors including Transcend and Kingston address their cards' address speed.42

This table lists accepted ratings, the minimum alteration rates, and the agnate Acceleration Chic (though the allegory is not consistently exact).

Appraisement Read Speed

(MB/s) Write Speed

(MB/s) Speed

Class

6× 0.9

10× 1.5

13× 2.0 2.0 2

26× 4.0 4.0 4

32× 4.8 5.0

40× 6.0 6.0 6

66× 10.0 10.0 10

100× 15.0 15.0

133× 20.0 20.0

150× 22.5 22.5

200× 30.0 30.0

266× 40.0 40.0

300× 45.0 45.0

400× 60.0 60.0

600× 90.0 90.0

edit UHS Acceleration Class

The Ultra-High Acceleration (UHS) interface is accessible on some SDHC and SDXC cards.43 The afterward ultra-high speeds are specified:

UHS-I cards, authentic in SD Version 3.01,39 abutment a alarm abundance of 100 MHz (a quadrupling of the aboriginal Default Speed), which in four-bit alteration approach could alteration 50 MB/s. UHS-I cards declared as UHS104 aswell abutment a alarm abundance of 208 MHz, which could alteration 104 MB/s. UHS-I is the alone chic for which articles are currently available.41

Double abstracts amount operation at 50 MHz (DDR50) is aswell authentic in Version 3.01, and is binding for microSDHC and microSDXC cards labeled as UHS-I. In this mode, four $.25 are transferred if the alarm arresting rises and addition four $.25 if it falls, appointment an absolute byte on anniversary abounding alarm cycle.

UHS-II cards, to be authentic in Version 4.0, added accession the abstracts alteration amount to a abstract best of 312 MB/s.2644

UHS anamnesis cards plan best with UHS host devices. The aggregate lets the user almanac HD resolution videos to tapeless camcorders while assuming added functions. It is aswell acceptable for real-time broadcasts and capturing ample HD videos.

Cards that accede with UHS appearance UHS-I or UHS-II on the label, and address this adequacy to the host device. Use of UHS requires th

Market penetration

Secure Agenda cards are acclimated in abounding customer cyberbanking devices, and accept become a boundless agency of autumn several gigabytes of abstracts in a baby size. Accessories area the user may abolish and alter cards often, such as agenda cameras, camcorders, and video bold consoles, tend to use full-sized cards. Accessories area baby admeasurement is paramount, such as adaptable phones, tend to use microSD cards. SD cards are not the a lot of economical band-aid in accessories that charge alone a baby bulk of non-volatile memory, such as base presets in baby radios. They may aswell not present the best best for applications area college accumulator capacities or speeds are a claim as provided by added beam agenda standards such as Compact Flash.

Many claimed computers of all types and claimed agenda administration (PDAs) use SD cards, either through congenital slots or through an alive cyberbanking adaptor. Adaptors abide for the PC card, ExpressBus, USB, FireWire, and the alongside printer port. Alive adaptors aswell let SD cards be acclimated in accessories advised for added formats. such as CompactFlash. The FlashPath adaptor lets SD cards be acclimated in a billowing deejay drive.

edit Agenda cameras

A camcorder with a 4 GB SDHC card

SD/MMC cards replaced Toshiba's SmartMedia as the ascendant anamnesis agenda architecture acclimated in agenda cameras. In 2001, SmartMedia had accomplished about 50% use, but by 2005 SD/MMC had accomplished over 40% of the agenda camera bazaar and SmartMedia's allotment had plummeted, with cards not getting calmly accessible in 2007.

At this time all the arch agenda camera manufacturers use SD in their customer artefact lines, including Canon, Casio, Fujifilm, Kodak, Leica, Nikon, Olympus, Panasonic, Pentax, Ricoh, Samsung, and Sony. Formerly, Olympus and Fujifilm acclimated XD-Picture Cards (xD cards) exclusively, while Sony alone acclimated Anamnesis Stick; about as of January 2010, all three abutment SD.

Some prosumer and able agenda camera models abide to action CompactFlash, either on a additional agenda aperture or as the alone storage, as they action abundant college capacities and faster alteration speeds and historically offered a bigger price/capacity arrangement as well.

Secure Agenda anamnesis cards can be acclimated in Sony XDCAM EX camcorders via the MEAD-SD01 adapter.45

edit Claimed computers

USB-based accepted Anamnesis agenda reader

Although abounding claimed computers board SD cards as an abetting accumulator accessory through a congenital aperture or a USB adaptor, SD cards cannot be acclimated as the primary harder deejay through the onboard ATA ambassador because none of the SD agenda variants supports ATA signalling. This use requires a abstracted SD ambassador chip46 or a SD-to-CompactFlash converter. However, on computers that abutment bootstrapping from a USB interface, an SD agenda in a USB adaptor can be the primary harder disk, provided it contains an operating arrangement that supports USB admission already the bootstrap is complete.

edit Embedded systems

This absorber (daughterboard) gives Arduino prototyping microprocessors admission to SD cards acquainted into the socket.

In 2008, the SDA defined Embedded SD, "leveraging acclaimed SD standards" to accredit non-removable SD-style accessories on printed ambit boards.47 SanDisk provides such anamnesis apparatus beneath the iNAND brand.48

Most avant-garde microcontrollers accept congenital SPI argumentation that can interface to a SD agenda operating in its SPI mode, accouterment non-volatile storage. Even if a microcontroller lacks the SPI feature, the affection can be emulated by bit banging. For example, a home-brew drudge combines additional General Purpose Input/Output (GPIO) pins of the processor of the Linksys WRT54G router with MMC abutment cipher from the Linux kernel.49 This address can accomplish throughput of up to 1.6 Mbit/s.

History

In 1999, SanDisk, Matsushita, and Toshiba agreed to advance and bazaar the Secure Agenda (SD) Anamnesis Card, which was a development of the MultiMediaCard (MMC). The new agenda provided both agenda rights administration (DRM) up to the Secure Agenda Music Initiative (SDMI) standard, and a top anamnesis body for the time.

The new architecture was advised to attempt with the Anamnesis Stick, a DRM artefact that Sony appear the above-mentioned year. It was afield predicted that DRM features50 would be broadly acclimated due to burden from music and added media suppliers to anticipate piracy.

The trademarked SD logo was originally developed for the Super Body Disc, which was the bootless Toshiba admission in the DVD architecture war. This is why the D resembles an optical disc.

At the 2000 Consumer Electronics Appearance (CES) barter show, the three companies appear the conception of the SD Agenda Association (SDA) to advance SD cards. The association's address are in California and it comprises some 30 companies that aftermath accessories and content. Early samples of the SD Agenda were accessible in the aboriginal division of 2000, with assembly quantities of 32 and 64 MB cards accessible 3 months later.

edit Relation to MMC

Size allegory of assorted beam cards: SD, CompactFlash, MMC, xD

The SD cards afflicted the MMC architecture in several ways:

Asymmetrical slots in the abandon of the SD agenda anticipate inserting it upside down, while an MMC will go in a lot of of the way but accomplish no acquaintance if inverted.

A lot of SD cards are 2.1 mm thick, compared to 1.4 mm for MMCs. The SD blueprint defines a agenda alleged Thin SD with a array of 1.4 mm, but they are rare, as the SDA went on to ascertain even abate anatomy factors.

The card's electrical contacts are recessed beneath the apparent of the card, attention them from acquaintance with a user's fingers.

The SD blueprint envisaged capacities and alteration ante beyond those of MMC, and these accept both developed over time. For a allegory table, see below.

Full-sized SD cards will not fit into the slimmer MMC slots, and there are added issues that affect the adeptness to use one architecture in a host accessory advised for the other.

edit Follow-on products

In March 2003, SanDisk Corporation appear the addition of the miniSD and accustomed it at CeBIT 2003.51 The SDA adopted the miniSD agenda in 2003 as a baby anatomy agency addendum to the SD agenda standard. While the new cards were advised abnormally for use in adaptable phones, they are usually packaged with a miniSD adapter which enables affinity with all accessories able with a accepted SD anamnesis agenda slot.

At CTIA Wireless 2005, the SDA appear the baby microSD anatomy agency (and SDHC, with capacities in balance of 2 GB and a minimum abiding apprehend and address acceleration of 17.6 Mbit/s). SanDisk had conceived microSD if its CTO and the CTO of Motorola assured that accepted anamnesis cards were too ample for adaptable phones. The agenda was originally alleged T-Flash, but just afore artefact launch, T-Mobile beatific a cease and abandon adjustment to SanDisk claiming that T-Mobile endemic the brand on T-(anything), and the name was afflicted to TransFlash. TransFlash and microSD cards are the same; anniversary can be acclimated in accessories fabricated for the other.52 SanDisk induced the SDA to administrate the microSD standard. The SDA accustomed the final microSD blueprint on July 13, 2005. Initially, microSD cards were accessible in capacities of 32, 64, and 128 MB.

In April 2006, the SDA appear a abundant blueprint for the non-security accompanying locations of the SD anamnesis agenda accepted and for the Secure Agenda Input Output (SDIO) cards and the accepted SD host controller.

In September, 2006, SanDisk appear the 4 GB miniSDHC.53 Like the SD and SDHC, the miniSDHC agenda has the aforementioned anatomy agency as the earlier miniSD agenda but the HC agenda requires HC abutment congenital into the host device. Accessories that abutment miniSDHC will plan with miniSD and miniSDHC, but accessories afterwards specific abutment for miniSDHC will plan alone with the earlier miniSD card.

In January 2009, the SDA appear the SDXC family, which supports cards up to 2 TB and speeds up to 300 Mbyte/s.

edit Openness of the standard

Dismantled microSD to SD adapter assuming the acquiescent affiliation from the microSD agenda aperture on the basal to the SD pins on the top

Like a lot of anamnesis agenda formats, SD is covered by abundant patents and trademarks. Royalties for SD agenda licences are imposed for accomplish and auction of anamnesis cards and host adapters (1000 USD/year additional associates at 1500 USD/year), but SDIO cards can be fabricated afterwards royalties.

Early versions of the SD blueprint were accessible alone afterwards accordant to a non-disclosure acceding (NDA) that banned development of an accessible antecedent driver. However, the arrangement was eventually reverse-engineered, and chargeless software drivers provided admission to SD cards that did not use DRM. Back then, the (SDA) has provided a simplified adaptation of the blueprint beneath a beneath akin license.54 Although a lot of open-source drivers were accounting afore this, it has helped them break affinity issues.

In 2006, the SDA aswell appear a simplified adaptation of the blueprint of the host ambassador interface (as against to the blueprint of SD cards) and afterwards aswell for the concrete layer, ASSD extensions, SDIO, and SDIO Bluetooth Type-A, beneath a disclaimers agreement.55 Again, a lot of of the advice had already been apparent and Linux had a absolutely chargeless disciplinarian for it. Still, architecture a dent befitting to this blueprint acquired the One Laptop per Child activity to affirmation "the aboriginal absolutely Accessible Antecedent SD implementation, with no charge to admission an SDI authorization or assurance NDAs to actualize SD drivers or applications."56

The actuality that the complete SD blueprint is proprietary mainly affects anchored systems and laptops, back users of desktop PCs about apprehend SD cards via USB-based agenda readers. These agenda readers present a accepted USB accumulation accumulator interface to anamnesis cards, appropriately amid the operating arrangement from the data of the basal SD interface. However, anchored systems (such as carriageable music players) usually accretion absolute admission to SD cards and appropriately charge complete programming information. Desktop agenda readers are themselves anchored systems; their manufacturers accept usually paid the SDA for complete admission to the SD specifications. Many anthology computers now cover SD agenda readers not based on USB; accessory drivers for these about accretion absolute admission to the SD card, as do anchored systems.

Technical details

Transfer modes

The concrete interface comprises 9 pins, except that the miniSD agenda adds two alone pins in the centermost and the microSD agenda omits one of the two VSS (Ground) pins.

SD agenda pin appointment miniSD agenda pin appointment microSD agenda pin assignment

SD agenda pinning.jpg Mini SD agenda pinning.jpg Micro SD agenda pinning.jpg

Various SD cards may abutment assorted combinations of the afterward bus types and alteration modes. The SPI bus and one-bit SD bus are binding for all SD families, as explained in the next section.

SPI: Consecutive Peripheral Interface Bus is primarily acclimated by anchored microcontrollers. This bus blazon supports alone a 3.3-volt interface.

One-bit SD: Abstracted command and abstracts channels and a proprietary alteration format.

Four-bit SD: Uses added pins additional some reassigned pins. UHS-I and UHS-II requires this bus type.

Once the host accessory and the SD agenda board a bus interface, the acceptance of the numbered pins is the aforementioned for all three agenda sizes:

SPI Bus Pin Name I/O Logic Description

1 nCS I PP Card Baddest (Neg True)

2 DI I PP Data In MOSI

3 VSS S S Ground

4 VDD S S Power

5 CLK I PP Clock SCLK

6 VSS S S Ground

7 DO O PP Data Out MISO

8 NC

nIRQ .

O .

OD NC (Memory Cards)

Interrupt (SDIO Cards)

9 NC . . NC

One-Bit SD Bus Pin Name I/O Logic Description

1 NC . . NC

2 CMD I/O PP,OD Command, Response

3 VSS S S Ground

4 VDD S S Power

5 CLK I PP Clock

6 VSS S S Ground

7 DAT0 I/O PP Data 0

8 NC

nIRQ .

O .

OD NC (Memory Cards)

Interrupt (SDIO Cards)

9 NC . . NC

Four-Bit SD Bus Pin Name I/O Logic Description

1 DAT3 I/O PP Data 3

2 CMD I/O PP,OD Command, Response

3 VSS S S Ground

4 VDD S S Power

5 CLK I PP Clock

6 VSS S S Ground

7 DAT0 I/O PP Data 0

8 DAT1

nIRQ I/O

O PP

OD Data 1. SDIO Cards share

with Interrupt Period

9 DAT2 I/O PP Data 2

Notes:

Direction is about to card. I = Input, O = Output.

PP = Push-Pull logic, OD = Open-Drain logic.

S = Adeptness Supply, NC = Not Connected (or analytic high).

edit Interface

Inside a 512 MB SD card: NAND beam dent that holds the abstracts (bottom) and SD ambassador (top)

Inside a 2 GB SD card: two NAND beam chips (top and middle), SD ambassador dent (bottom)

Inside a SDHC card

Command interface

SD cards and host accessories initially acquaint through a ancillary one-bit interface, area the host accessory provides a alarm arresting that strobes individual $.25 into and out of the SD card. The host accessory thereby sends 48-bit commands and receives responses. The agenda can arresting that a acknowledgment will be delayed, but the host accessory can arrest the dialogue.

Through arising assorted commands, the host accessory can:

Determine the type, anamnesis capacity, and capabilities of the SD card

Command the agenda to use a altered voltage, altered alarm speed, or avant-garde electrical interface

Prepare the agenda to accept a block to address to the beam memory, or apprehend and acknowledgment with the accommodation of a defined block.

The command interface is an addendum of the MultiMediaCard (MMC) interface. SD cards alone abutment for some of the commands in the MMC protocol, but added commands accompanying to archetype protection. By application alone commands accurate by both standards until free the blazon of agenda inserted, a host accessory can board both SD and MMC cards.

Electrical interface

All SD agenda families initially use a 3.3-volt electrical interface. On command, SDHC and SDXC cards about-face to 1.8-volt operation.39

At antecedent power-up or agenda insertion, the host accessory selects either the Consecutive Peripheral Interface (SPI) bus or the one-bit SD bus by the voltage akin present on Pin 1. Thereafter, the host accessory may affair a command to about-face to the four-bit SD bus interface, if the SD agenda supports it. For assorted agenda types, abutment for the four-bit SD bus is either alternative or mandatory.39

After free that the SD agenda supports it, the host accessory can aswell command the SD agenda to about-face to a college alteration speed. Until free the card's capabilities, the host accessory should not use a alarm acceleration faster than 400 kHz. SD cards added than SDIO (see below) accept a Default Acceleration alarm amount of 25 MHz. The host accessory is not appropriate to use the best alarm acceleration that the agenda supports. It may accomplish at beneath than the best alarm acceleration to conserve power.39 Amid commands, the host accessory can stop the alarm entirely.

SDIO cards

The SDIO ancestors comprises Low-Speed and Full-Speed cards. Both types of SDIO cards abutment SPI and one-bit SD bus types. Low-Speed SDIO cards are accustomed to aswell abutment the four-bit SD bus; Full-Speed SDIO cards are appropriate to abutment the four-bit SD bus. To use a SDIO agenda as a "combo card" (for both anamnesis and I/O), the host accessory accept to aboriginal baddest four-bit SD bus operation. Two added altered appearance of Low-Speed SDIO are a best alarm amount of 400 kHz for all communications, and the use of Pin 8 as "interrupt" to try to admit chat with the host device.57

Ganging cards together

The one-bit SD agreement was acquired from the MMC protocol, which envisaged the adeptness to put up to 3 cards on a bus of accepted arresting lines. The cards use accessible beneficiary interfaces, area a agenda may cull a band to the low voltage level; the band is at the top voltage akin (because of a pull-up resistor) if no agenda pulls it low. Though the cards aggregate alarm and arresting lines, anniversary agenda had its own dent baddest band to faculty that the host accessory had alleged it.

The SD agreement envisaged the adeptness to assemblage 30 cards calm after abstracted dent baddest lines. The host accessory would advertisement commands to all cards and analyze the agenda to acknowledge to the command application its altered consecutive number.

In practice, cards are rarely ganged calm because open-collector operation has problems at top speeds and increases adeptness consumption. Newer versions of the SD blueprint acclaim abstracted curve to anniversary card.

Achieving college agenda speeds

The SD blueprint defines four-bit-wide transfers. (The MMC blueprint supports this and aswell defines an eight-bit-wide mode.) Transferring several $.25 on anniversary alarm beating improves the agenda speed. Avant-garde SD families accept aswell bigger acceleration by alms faster alarm frequencies and bifold abstracts amount (explained here).

edit Book system

Like added types of beam anamnesis card, an SD agenda of any SD ancestors is a block-addressable accumulator device, in which the host accessory can apprehend or address fixed-size blocks by allegorical their block number.

MBR and FAT

Most SD cards address preformatted with one or added MBR partitions, area the aboriginal or alone allotment contains a book system. This lets them accomplish like the harder deejay of a claimed computer. Per the SD agenda specification, an SD agenda is formatted with MBR and the afterward book system:

For SDSC cards: FAT16

For SDHC cards: FAT32

For SDXC cards: exFAT

Most customer articles that yield an SD agenda will apprehend it to be abstracted and formatted in this way. The accepted abutment for FAT16 and FAT32 acquiesce the acceptance of SDSC and SDHC cards on a lot of host computers with a accordant SD reader, to present the user with the accustomed adjustment of alleged files in a hierarchical agenda tree.

On such SD cards, accepted account programs such as Mac OS X's "Disk Utility" or Windows' SCANDISK can be acclimated to adjustment or retrieve besmirched data, and sometimes balance deleted files. Defragmentation accoutrement for FAT book systems may be acclimated on such cards. The consistent alliance of files may accommodate a bordering advance in the time appropriate to apprehend or address the file,40 but not an advance commensurable to defragmentation of harder drives, area autumn a book in assorted bits may absorb a time amends to move amid concrete areas of the drive. Moreover, defragmentation performs writes to the SD agenda that calculation adjoin the card's rated lifespan. The address ability of the concrete anamnesis is discussed in the commodity on beam memory; newer technology to admission the accumulator accommodation of a agenda currently provides worse address endurance.

When reformatting an SD agenda abate than 4 GB, FAT16 should be used. (This is aswell an advantage for 4 GB cards, but it requires the use of 64 kiB clusters, which are not broadly supported.) FAT16 does not abutment cards aloft 4 GB.

The SDXC blueprint makes Microsoft's proprietary exFAT book arrangement mandatory,58 which is accurate alone by some proprietary operating systems.

Other book systems

Because the host angle the SD agenda as a block accumulator device, the agenda does not crave MBR partitions or any specific book system. The agenda can be reformatted to use any book arrangement the operating arrangement supports. For example:

Under Unix-like operating systems such as Linux or FreeBSD, SD cards can be formatted application the UFS, EXT3, ext4, btrFS, HFS Plus, or the ReiserFS book systems.

Under Mac OS X, SD cards can be abstracted as GUID accessories and formatted with the HFS Additional book system.

Under Windows and some Unix systems, SD cards can be formatted application NTFS and, on after versions, exFAT.

Additionally, an SD agenda alleged Live SD can accommodate an anchored operating arrangement (such as Live USB). Computers that can bootstrap from an SD agenda (either application a USB adapter or amid into the computer's beam media reader) instead of the harder deejay drive may thereby be able to balance from a besmirched harder deejay drive. A Live SD can be write-locked to bottle the system's integrity.

Risks of reformatting

Reformatting an SD agenda with a altered book system, or even with the aforementioned one, may accomplish the agenda slower, or abbreviate its lifespan. Some cards use abrasion leveling, in which frequently adapted blocks are mapped to altered portions of anamnesis at altered times, and some wear-leveling algorithms are advised for the admission patterns archetypal of the book allocation table on a FAT16 or FAT32 device.59 In addition, the preformatted book arrangement may use a array admeasurement that matches the abolish arena of the concrete anamnesis on the card; reformatting may change the array admeasurement and accomplish writes beneath efficient.

edit Adeptness use

The adeptness burning of microSD cards varies by manufacturer, but appears to be in the ambit of 66-330 mW (20-100 mA at a accumulation voltage of 3.3 V). Specifications from TwinMos technologies account a best of 149 mW (45 mA) during transfer. Toshiba, on the added hand, lists 264-330 mW (80-100 mA).60

Storage capacity and incompatibilities

All SD cards let the host accessory actuate how abundant advice the agenda can hold, and the blueprint of anniversary SD ancestors gives the host accessory a agreement of the best accommodation a adjustable agenda will report.

By the time the Adaptation 2.0 (SDHC) blueprint was completed in June 2006,61 vendors had already devised 2 GB and 4 GB SD cards, either as defined in Adaptation 1.01, or by creatively account Adaptation 1.00. The consistent cards do not plan accurately in some host devices.6263

edit SDSC cards aloft 1 GB

4 GB SDSC card

A host accessory can ask any amid SD agenda for its 128-bit identification cord (the Card-Specific Abstracts or CSD). In standard-capacity cards (SDSC), 12 $.25 analyze the amount of anamnesis clusters (ranging from 1 to 4,096) and 3 $.25 analyze the amount of blocks per array (which break to 4, 8, 16, 32, 64, 128, 256, or 512 blocks per cluster). The host accessory multiplies these abstracts (as apparent in the afterward section) with the amount of bytes per block to actuate the card's accommodation in bytes.

In SD adaptation 1.00, the amount of bytes per block was affected to be 512. This acceptable SDSC cards up to 4,096 × 512 × 512 = 1 GB, for which there are no accepted incompatibilities.

Version 1.01 let an SDSC agenda use a 4-bit acreage to announce 1,024 or 2,048 bytes per block instead.39 Doing so enabled cards with 2 GB and 4 GB capacity.

Early SDSC host accessories that accept 512-byte blocks accordingly will not absolutely abutment the admittance of 2 GB or 4 GB cards. In some cases, the host accessory can apprehend abstracts that happens to abide in the aboriginal 1 GB of the card. If the acceptance is fabricated in the disciplinarian software, success may alter from one adaptation of Windows to another. In addition, any host accessory ability not abutment a 4 GB SDSC card, back the blueprint lets it accept that 2 GB is the best for these cards.

edit Storage accommodation calculations

The architecture of the Card-Specific Abstracts (CSD) annals afflicted amid adaptation 1 (SDSC) and adaptation 2.0 (which defines SDHC and SDXC).

Version 1

In Adaptation 1 of the SD specification, accommodation is affected by accumulation fields of the CSD as follows:

Capacity=(C_SIZE+1)<<(C_SIZE_MULT+2)<<="" p="">

Where 0<=C_SIZE<=4095, 0<=C_SIZE_MULT<=7, READ_BL_LEN==9 || READ_BL_LEN==10

Later versions accompaniment (at Area 4.3.2) that a 2 GB SDSC agenda shall set its READ_BL_LEN (and WRITE_BL_LEN) to announce 1024 bytes, so that the aloft ciphering accurately letters the card's capacity; but that, for consistency, the host accessory shall not appeal (by CMD16) block lengths over 512 bytes.39

Versions 2 and 3

In the analogue of SDHC cards in Adaptation 2.0, the C_SIZE allocation of the CSD is 22 $.25 and it indicates the anamnesis admeasurement in multiples of 512 KB. (The C_SIZE_MULT acreage is removed and READ_BL_LEN is no best acclimated to compute capacity.) Two $.25 that were aforetime aloof now analyze the agenda family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved.39 Because of these redefinitions, earlier host accessories do not accurately analyze SDHC or SDXC cards nor their actual capacity.

SDHC cards are belted to advertisement a accommodation not over 32 GiB.

SDXC cards are accustomed to use all 22 $.25 of the C_SIZE field. An SDHC agenda that did so (reported C_SIZE > 65375 to announce a accommodation of over 32 GiB) would breach the specification. A host accessory that relied on C_SIZE rather than the blueprint to actuate the card's best accommodation ability abutment such a card, but the agenda ability abort in added SDHC-compatible host devices.

Capacity is affected thus:

Capacity=(C_SIZE+1)*524288

where for SDHC 4112<=C_SIZE<=65375 (approx. 2 GB) < accommodation < 32 GiB

for SDXC 65535<=C_SIZE 32 GiB <= accommodation <= 2 TiB max.

Capacities aloft 4 GB can alone be accomplished by afterward Adaptation 2.0 or after versions. In addition, capacities according to 4 GB have to aswell do so to agreement compatibility.

Comparison to other flash memory formats

Overall, SD is beneath accessible than CompactFlash or USB beam anamnesis drives; these are accessible standards which can be implemented chargeless of transaction for licensing, royalties, or documentation. (CompactFlash and USB beam drives may, however, crave licensing fees for the use of the SDA's trademarked logos.)

However, SD is abundant added accessible than Anamnesis Stick, for which no accessible affidavit nor any accurate bequest accomplishing is available. All SD cards can be accessed advisedly application the well-documented SPI bus.

xD cards are artlessly 18-pin NAND beam chips in a appropriate amalgamation and abutment the accepted command set for raw NAND beam access. Although the raw accouterments interface to xD cards is able-bodied understood, the blueprint of its anamnesis contents—necessary for interoperability with xD agenda readers and agenda cameras—is absolutely undocumented. The bunch that licenses xD cards has not appear any abstruse advice to the public.