Secure Digital: Difference between revisions

From Wikipedia, the free encyclopedia
Jump to: navigation, search
m (Reverted edits by 208.79.10.6 to last version by Neurolysis (HG))
(Replaced content with 'kimmy is single corbin loves brittany smith cole and alexa r daten madeline is single soo any hot guys 14-16 holla at er')
Line 1: Line 1:
{{Refimprove|date=July 2008}}
 
  +
kimmy is single
{{Cleanup|date=June 2008}}
 
  +
corbin loves brittany smith
{{Infobox media
 
  +
cole and alexa r daten
| name = Secure Digital
 
  +
madeline is single soo any hot guys 14-16 holla at er
| logo =
 
| image = [[Image:SD Cards.png|250px]]
 
| caption = Pair of SD cards
 
| type = [[Memory card]]
 
| encoding =
 
| capacity = Standard SD: 8&nbsp;MB to 4&nbsp;GB <br> SDHC: 1&nbsp;GB to 32&nbsp;GB <ref>pricerunner.com 2008-08-27</ref> (theoretical max for SDHC is 2&nbsp;TB.)<!-- Both standard-SD and SDHC can have 4 GB capacity! , and yes there are less than 4GB SDHC -->
 
| read =
 
| write =
 
| standard =
 
| owner = [[SD Card Association]]
 
| use = Portable devices, including digital cameras and handheld computers
 
| extended from = [[MultiMediaCard]] (MMC)
 
| extended to =
 
}}
 
 
'''Secure Digital''' ('''SD''') is a [[non-volatile memory|non-volatile]] [[memory card]] format developed by [[Matsushita Electric Industrial Co.|Matsushita]], [[SanDisk]], and [[Toshiba]] for use in portable devices. Today it is widely used in [[digital cameras]], [[mobile device|handheld computers]], [[Personal digital assistant|PDA]]s, [[mobile phone]]s, [[GPS]] receivers, and [[video game console]]s. Standard SD card capacities range from 8 [[megabyte|MB]] to 4 [[gigabyte|GB]] and for high capacity SDHC cards 4 GB to 32 GB as of 2008.<!-- Both standard-SD and SDHC can have 4 GB capacity!, however less than 4 GB SHDC cards are pointless -->
 
 
The format has proven to be very popular. However, a change in the format, while allowing capacities greater than 4 GB ([[Secure_Digital_card#SDHC|SDHC]]), has created compatibility issues with older devices which cannot read the new format. Since SDHC format cards have the same physical shape and form factor as the older format, this has caused considerable confusion for consumers.<ref>{{cite web|url=http://www.dramexchange.com/WeeklyResearch/Post/1/492.aspx dramexchange.com/WeeklyResearch/Post/1/492.aspx |title=A look into how SDHC will affect the future Nand Flash market|publisher=DRAMeXchange|date=2006-12-05|accessdate=2008-05-13}}</ref><ref>{{cite web|url=http://pocketpccentral.net/news/7-18-06_sdhc_ppcs.htm pocketpccentral.net |title=Pocket PC Users steer clear of SDHC... For Now|publisher=Pocket PC Central Press|date=2006-07-18|accessdate=2008-05-13}}</ref> SDHC cards require an SDHC capable device [[firmware]], generally not found with older devices.
 
 
== History ==
 
 
In August of 1999, [[Panasonic]], [[SanDisk]], and [[Toshiba]] first agreed to develop and market the SD (Secure Digital) Memory Card, which was a development of the [[Multi Media Card|MMC]]. With a physical profile of 24&nbsp;mm × 32&nbsp;mm × 2.1&nbsp;mm, the new card provided both [[Digital rights management|DRM]] up to the [[Secure Digital Music Initiative|SDMI]] standard, and a high memory density for the time.
 
 
The new format was designed to compete with [[Sony]]'s [[Memory Stick]] format that was released the previous year, which featured [[MagicGate]] DRM, and was physically larger. It was thought that DRM features [http://www.toshiba.co.jp/about/press/2003_07/pr1701.htm] would be widely used due to pressure from music and other media suppliers to prevent piracy. The features are largely unused.
 
 
At the 2000 [[Consumer Electronics Show|CES]] trade show Matsushita, SanDisk and Toshiba Corporation announced the creation of the [[SD Card Association]],to promote SD cards. It is headquartered in California and its executive membership includes some 30 world-leading high-tech companies and major content companies. Early samples of the SD Card were available in the first quarter of 2000, with production quantities of 32 and 64 [[megabyte]]s available 3 months later.
 
 
In April 2006, the SDA released a detailed specification for the non-security related portions of the SD Memory Card standard. In addition, they released specifications for the SDIO (Secure Digital Input Output) cards and the standard SD host controller. During the same year, specifications were finalised for the small form-factor [[microSD]] (formerly known as TransFlash) and SDHC, with capacities in excess of 2&nbsp;GB and a minimum sustained read/write speed of 2.2&nbsp;MB/s.
 
 
== Design and implementation ==
 
[[Image:SD Cards.svg|thumb|right|250px|An SD card, mini SD card, and micro SD card from top to bottom.]]
 
 
SD cards are based on the older [[MultiMediaCard]] (MMC) format, but have a number of differences:
 
 
* The SD card is asymmetrically shaped in order not to be inserted upside down, while an MMC would go in most of the way but not make contact if inverted.
 
* Most SD cards are physically thicker than MMCs. SD cards generally measure 32&nbsp;mm × 24&nbsp;mm × 2.1&nbsp;mm, but can be as thin as 1.4&nbsp;mm, just like MMCs (see below).
 
* The contacts are recessed beneath the surface of the card, protecting the contacts from contact with the fingers.
 
* SD cards typically have transfer rates in the range of 10-20 MBytes/s, but this is always changing, particularly in light of recent improvements to the [[MMC]] standard.<ref>See [[Comparison of memory cards]].</ref>
 
 
Devices with '''SD''' slots can use the thinner MMCs, but the standard SD cards will not fit into the thinner MMC slots. [[MiniSD Card|miniSD]] and [[microSD]] cards can be used directly in SD slots with a simple passive adapter, since they differ in size and shape but not electrical interface. With an active electronic adapter, SD cards can be used in [[CompactFlash]] or [[PC card]] slots. Some SD cards include a USB connector for compatibility with desktop and laptop computers, and [[card reader]]s allow SD cards to be accessed via connectivity ports such as [[USB]], [[FireWire]], and the [[parallel port|parallel printer port]]. SD cards can also be accessed via a [[floppy disk]] drive with a [[FlashPath]] adapter.
 
 
=== Optional write-protect tab ===
 
 
When looking at the card from the top (see pictures) there is one required notch on the right side (the side with the diagonal notched corner).
 
 
On the left side there is usually a slidable tab. This is the [[write protection|write-protect tab]]. The MMC has neither notch. It is easy to mistake this tab as an electronic on/off switch built inside the card, but it is used simply as a tab/notch switch. The tab/notch works the same way as the notches on [[compact audio cassette]]s and [[videotape]] cassette [[magnetic tape|tape]]s or [[floppy disk]]s, where the device senses the tab/notch and determines if the card is write-protected or not.
 
 
When this write-protect tab is in the down position (away from the end that is inserted) then it is write protected and read-only. When the tab is in the up position it is write enabled. Since the tab is optional, the card can have no switch and no notch, which makes the card '''always''' writable, or it can have an empty notch and be a ROM card, which makes the card '''always''' write-protected and read-only. If the tab becomes broken or falls off then the card will become a write-protected [[read-only memory|ROM]] card and no longer be writable. A possible troubleshooting solution would be to apply tape over the notched area (avoiding the connectors and the other notch) to configure the card in a permanent writable state.
 
 
If the sensor inside the device is faulty and unable to detect the tab/notch, all SD cards will seem to be either write-protected or write-enabled, depending on the failure mode.
 
 
The write protect tab feature is optional within the Secure Digital Association guidelines. Some manufacturers claim that the write switch is easily broken, and do not include it on all their card models.<ref>[http://www.kingmaxdigi.com/support/faq.htm kingmaxdigi.com, Kingmax FAQ 2006]</ref> For writable cards, this is simply a matter of changing the molding of the outer shell so that the notch doesn't exist.
 
 
Some music and film media companies (e.g. [[Disney]]) have released limited catalogs of records and/or videos on SD. These usually contain [[Digital Rights Management|DRM]]-encoded [[Windows Media]] files, making use of the SD format's DRM capabilities. Such media is usually permanently marked read-only, by adding the notch with no tab. These cards could be further protected (and possibly produced more cheaply) by manufacturing the card with true [[Read-only memory|ROM]] rather than flash memory; it is not clear if any vendors have taken this approach.
 
 
=== File system ===
 
 
Like other flash card technologies, most SD cards ship preformatted with the [[File Allocation Table|FAT]] or [[File_Allocation_Table#FAT32|FAT 32]] [[file system]]. The ubiquity of this file system allows the card to be accessed on virtually any host device with an SD reader. Also, standard FAT maintenance utilities (e.g. [[ScanDisk]]) can be used to repair or retrieve corrupted data. However, because the card appears as a removable hard drive to the host system, the card can be reformatted to any file system supported by the operating system.
 
 
[[Defragmentation]] tools are used on hard disks to optimise the filesystem access speed. On an SD card, this is pointless, as any block can be accessed as fast as any other. Doing this will wear the card out slightly, as only so many writes can be made before failure.
 
 
However, note that any file recovery tool will struggle to recover files from highly fragmented data if the File Allocation Table becomes highly corrupted.
 
 
== Speeds ==
 
 
There are different speed grades available which are measured with the same system as [[CD-ROM]]s, in multiples of 150&nbsp;[[kilobyte|kB]]/s (1x = 150 kB/s). Basic cards transfer data up to six times (6x) the data rate of the standard CD-ROM speed (900 kB/s vs. 150 kB/s). High-speed cards are made with higher data transfer rates like 66x (10&nbsp;[[Megabyte|MB]]/s), and high-end cards have speeds of 200x or higher. Note that maximum ''read'' speed and maximum ''write'' speed may be different, with maximum write speed typically lower than maximum read speed. Some [[digital cameras]] require high-speed cards (write speed) to record video smoothly or capture multiple still photographs in rapid succession. The SD card specification 1.01 allows for a maximum speed of 66x. Higher speeds of up to 200x are defined by specification 2.0.
 
 
The following table lists some common ratings and their respective '''maximum''' transfer rates.
 
 
{| align=center class=wikitable
 
! Rating
 
! Speed (MB/s)
 
|-
 
| align="center" | &nbsp;&nbsp;6x
 
| align="center" | &nbsp;0.9
 
|-
 
| align="center" | &nbsp;32x
 
| align="center" | &nbsp;4.8
 
|-
 
| align="center" | &nbsp;40x
 
| align="center" | &nbsp;6.0
 
|-
 
| align="center" | &nbsp;66x
 
| align="center" | 10.0
 
|-
 
| align="center" | 100x
 
| align="center" | 15.0
 
|-
 
| align="center" | 133x
 
| align="center" | 20.0
 
|-
 
| align="center" | 150x
 
| align="center" | 22.5
 
|-
 
| align="center" | 200x
 
| align="center" | 30.0
 
|}
 
 
== Openness of standards ==
 
 
{{quote box2
 
|width = 0px
 
|border = 1px
 
|quote =[[Image:Sd insides.png|180px]] The inside of a Samsung 512 MB SD Card. The top chip is the SD [[controller (computing)|controller]] and the bottom one is the [[NAND flash]] chip that actually stores the data.}}
 
[[Image:SanDisk 128MB SD Card Insides.png|thumb|The internal components of a SanDisk 128 MB SD Card.]]
 
 
Like most memory card formats, SD is covered by numerous [[patent]]s (e.g. [http://findarticles.com/p/articles/mi_m0EKF/is_47_46/ai_69236951 US patent 5602987]) and [[trademark]]s.
 
 
There are <!-- at least --> three versions of the SD specification: 1.0, 1.1 and 2.0. These were originally only available after agreeing to a [[non-disclosure agreement]] (NDA) which prohibits the development of an [[open source]] driver, a fact that generates a fair amount of consternation in the open-source and [[free software]] communities. The system was eventually [[reverse-engineered]] though, and the non-DRMed sections of the memory cards could be accessed by free software drivers.
 
 
These days however, the [[SD Card Association]] (SDA) has made access to a simplified version of the specification available under a less-restrictive licence.<ref>[http://www.newsforge.com/article.pl?sid=01/12/20/2224254&mode=thread Sharp Linux PDA promotes use of proprietary SD card, but more open MMC works just fine]</ref> Although most open-source drivers were written before this, it has helped them to solve some compatibility issues.
 
 
In 2006, the SD Card Association also released a simplified version of their host controller interface specification (not to be confused with the physical specification, which covers the actual cards and their protocol).<ref>[http://www.sdcard.org/about/host_controller/simple_spec Simplified SD Host Controller Spec] from the SDA's website</ref> Like the physical specification, most of the information had already been discovered before the public release<ref>[http://mmc.drzeus.cx/wiki/Controllers/SDHCI Reverse-engineered register information for the standard host controller]</ref> and at least [[Linux]] had a fully free driver for it. Still, building a chip conforming to this specification caused the [[One Laptop Per Child]] project to claim "the first truly Open Source SD implementation, with no need to obtain an SDI license or sign NDAs to create SD drivers or applications."<ref>[http://mailman.laptop.org/pipermail/community-news/2006-September/000023.html OLPC mailing list archive]</ref>
 
 
For the most part, the lack of complete, open SD specifications mainly affects [[embedded system]]s, since desktop users generally read SD cards via [[USB]]-based [[card reader#Memory card readers|card reader]]s. These card readers present a standard [[USB mass storage]] interface to memory cards, thus separating the operating system from the details of the underlying SD interface. However, embedded systems (such as portable music players) usually access SD cards directly, and therefore complete programming information is necessary. Desktop card readers are themselves examples of such embedded systems; the manufacturers of these readers have usually paid the SDCA for complete access to the SD specifications. Many notebook computers now include SD card readers ''not'' based on USB; device drivers for these essentially access the SD card directly, as in embedded systems.
 
 
=== Technical explanation ===
 
 
SD supports at least three transfer modes:
 
 
* One-bit SD mode (separate command and data channels and a proprietary transfer format)
 
* Four-bit SD mode (uses extra pins plus some reassigned pins)
 
* SPI mode (basically, a simpler subset of the SD protocol for use with [[microcontrollers]])
 
 
All memory cards must support all three modes, except for microSD where SPI is optional. The cards must also support clock frequencies of up to 25&nbsp;MHz for regular cards, and 50&nbsp;MHz for high-speed cards.
 
 
Royalties for SD/SDIO licenses are imposed for manufacture and sale of memory cards and host adapters (1000 USD per year plus membership at 1500 USD/year) but [[Secure_digital_card#SDIO|SDIO]] cards can be made without royalties and MMC host adapters do not require a royalty. MMCs have a seven-pin interface; SD and SDIO have expanded this to nine pins and MMC Plus expands this even further with thirteen pins.
 
 
=== DRM features ===
 
 
The [[digital rights management]] scheme embedded in the SD cards is defined as the [[Content Protection for Recordable Media]] (CPRM) by the [[4C Entity]] and is centered around use of the [[Cryptomeria cipher]] (also known as ''C2''). The specification is kept secret and is only accessible to licensees. [[DVD-Audio]] uses a very similar scheme known as Content Protection for Prerecorded Media (CPPM). This type of DRM is associated with [[SDMI]], an organisation set up by the [[RIAA]] to promote such hardware-based copy protection schemes. Many SD cards are marked on the packaging as being 'SDMI Compliant' for this reason. This DRM has not been seen "in the wild" and few, if any, devices appear to provide support for it.
 
 
Super*Talent, a manufacturer of computer memory, has created the "Super Digital" card. They are the same in appearance and function to regular Secure Digital cards, but they lack the CPRM code commonly found in Secure Digital cards. <ref>[http://www.supertalent.com/products/sd.php Super Talent Technology - DDR and DDR2 Memory<!-- Bot generated title -->]</ref>
 
 
=== Compared to other flash memory formats ===
 
 
Overall, SD is less open than [[CompactFlash]] or [[USB flash drive|USB flash memory drives]], which can be implemented for free but require licensing fees for the associated logos and trademarks.
 
 
However, SD is much more open than [[Memory Stick]], for which no public documentation nor any documented legacy implementation is available. All SD cards can, at least, be accessed freely using the well-documented SPI/MMC mode.
 
 
[[xD-Picture Card|xD]] cards are simply 18-pin [[NAND flash]] chips in a special package, and support [[XD-Picture Card#Raw hardware|the standard command set]] for raw NAND flash access. Although the raw hardware interface to xD cards is well-understood, the layout of its memory contents--necessary for interoperability with xD card readers and digital cameras--is totally undocumented. The consortium that licenses xD cards has not released any publicly available technical information.
 
 
== Different types of MMC/SD cards ==
 
 
The SD card is not the only flash [[memory card]] standard ratified by the Secure Digital Card Association. Other SD Card Association formats include [[miniSD Card|miniSD]], [[microSD]] (formerly known as [[microSD|TransFlash]] before ratification by the SD Card Association), and SDHC (Secure Digital High Capacity, for capacities above 4 GB - although, there are cards some readers can't handle over 1 GB that are not SDHC). SDHC is not fully compatible with the format that it extends, in that SD devices that do not specifically support SDHC will not work with the newer cards.
 
 
These smaller miniSD and microSD cards are usable in full size MMC/SD/SDIO slots with an adapter (which must route the electrical connections as well as making physical contact). It should be noted, however, that it is already difficult to create I/O devices in the SD form factor and this will be even more difficult in the smaller sizes. However, a WiFi card for mini-SDIO is already available from Spectec.<ref>[http://www.spectec.com.tw/wlan.html Spectec's WiFi SDIO products]</ref>
 
 
As SD slots still support MMCs, the separately-evolved smaller MMC variants are also compatible with SD-supporting devices. Unlike [[miniSD Card|miniSD]] and [[microSD]] (which are sufficiently different from SD to make mechanical adapters necessary), RS-MMC slots maintain backward compatibility with full-sized MMCs, because the RS-MMCs are simply shorter MMCs. More information on these variants can be found in the article about the [[MultiMediaCard]] standard.
 
 
It is also important to note, that unlike for data storage (which typically works everywhere an SD slot is present), an SDIO device must be supported and equipped with drivers and applications for the host system and usually doesn't work outside of the manufacturer's scope (which means, for example, that an HP SDIO camera usually does not work with PDAs for which it is not listed as an accessory). This behavior is often not expected by end users who typically expect that only the SD slot is required. Similar compatibility are sometimes seen with [[Bluetooth]] devices, although to a much lesser extent thanks to standardized [[bluetooth profiles]].
 
 
Most, possibly all, current MMC flash memory cards support SPI mode even if not officially required as failure to do so would severely affect compatibility. All cards currently made by SanDisk, [[Ridata|Ritek/Ridata]], and Kingmax digital appear to support SPI. Also, MMCs may be electrically identical to SD cards but in a thinner package and with an electronic fuse blown to disable SD functionality (so no SD royalties need to be paid).
 
Some MicroSD cards do not support SPI mode.
 
 
MMC defined the SPI and one-bit MMC/SD protocols. The underlying SPI protocol has existed for years as a standard feature on many microcontrollers. From a societal perspective, the justification for a new incompatible SD/MMC protocol is questionable; the development of a new incompatible and unnecessary protocol may help trade associations collect licensing and membership fees but it raises the cost of hardware and software in many ways. The new protocol used [[open collector]] signaling to allow multiple cards on the same bus but this actually causes problems at higher clock rate. While SPI used three shared lines plus a separate chip select to each card, the new protocol allows up to 30 cards to be connected to the same three wires (with no chip select) at the expense of a much more complicated card initialization and the requirement that each card have a unique serial number for plug and play operation; this feature is rarely used and its use is actively discouraged in new standards (which recommend a completely separate channel to each card) because of speed and power consumption issues. The quasi-proprietary one-bit protocol was extended to support four bit wide (SD and MMC) and eight bit (MMC only) transfers for more speed while much of the rest of the computer industry is moving to higher speed narrower channels; standard SPI could simply have been clocked at higher data rates (such as 133&nbsp;MHz) for higher performance than offered by four-bit SD — embedded CPUs that did not already have higher clock rates available would not have been fast enough to handle the higher data rates anyway. The SD card association dropped support for some of the old one-bit MMC protocol commands and added support for additional commands related to copy protection.
 
 
=== Compatibility issues with 2 GB and larger cards ===
 
 
Devices that use SD cards identify the card by requesting a 128-bit identification string from the card. For standard-capacity SD cards, 12 of the bits are used to identify the number of memory clusters (ranging from 1 to 4096) and 3 of the bits are used to identify the number of blocks per cluster (which decode to 4, 8, 16, 32, 64, 128, 256 or 512 blocks per cluster).
 
 
In older 1.x implementations the standard capacity block was exactly 512 bytes. This gives 4096 x 512 x 512 = 1 gigabyte of storage memory. A later revision of the 1.x standard allowed a 4-bit field to indicate 1024 or 2048 bytes per block instead, yielding more than 1 gigabyte of memory storage.
 
Devices designed before this change may incorrectly identify such cards, usually by misidentifying a card with lower capacity than is the case by assuming 512 bytes per block rather than 1024 or 2048. <!-- In case of dispute, provide working link to the 1.x standard from sd card assoc -->
 
 
For the new SDHC high capacity card (2.0) implementation, 22 bits of the identification string are used to indicate the memory size in increments of 512 KBytes. Currently 16 of the 22 bits are allowed to be used<!-- why did sd-assoc borked this feature?? -->, giving a maximum size of 32 GB. All SDHC 4-GB and larger cards must be 2.0 implementations. Two bits that were previously reserved and fixed at 0 are now used for identifying the type of card, 0=standard, 1=HC, 2=reserved, 3=reserved<!-- check type -->. Non-HC devices are not programmed to read this code and therefore cannot correctly read the identification of the card.
 
 
All SDHC readers work with standard SD cards.<ref>[http://www.hjreggel.net/cardspeed/special-sd.html SD Compatibility], CARDSPEED - Card Readers and Memory Cards, December 1, 2006</ref>
 
 
Many older devices will not accept the 2 or 4 GB size even though it is in the revised standard. The following statement is from the SD association specification:
 
:"To make 2 GByte card, the Maximum Block Length (READ_BL_LEN=WRITE_BL_LEN) shall be set to 1024 bytes. However, the Block Length, set by CMD16, shall be up to 512 bytes to keep consistency with 512 bytes Maximum Block Length cards (Less than and equal 2 Gbyte cards)."<ref name="sdca-2gb">{{cite book
 
| last = SD Group Technical Committee
 
| title = SD Specifications, Part 1: Physical Layer Simplified Specification
 
| url = http://www.sdcard.org/sd_memorycard/Simplified%20Physical%20Layer%20Specification.PDF
 
| format = [[PDF]], [http://72.14.209.104/search?q=cache:lVMIQpGALuUJ:www.sdcard.org/sd_memorycard/Simplified%2520Physical%2520Layer%2520Specification.PDF+%22Physical+Layer+Simplified+Specification%22&hl=en&ct=clnk&cd=1&gl=us&client=firefox-a HTML]
 
| accessdate = 2007-02-23
 
| edition = Version 2.00
 
| date = September 25, 2006
 
| publisher = SD Card Association
 
| pages = p. 19
 
| chapter = Section 4: SD Memory Card Functional Description; 4.3.2: 2 Gbyte Card
 
}}</ref>
 
 
=== SD (non-SDHC) cards with greater than 1 GB capacity ===
 
 
The [[SD Card Association]]'s current specifications defines how a standard SD card (non-SDHC) card with more than 1 GB and up to 4 GB capacity should be designed. These cards should be readable in any SD 1.01 devices that takes the block length data into account. Any 1 GB or lesser card should always work. (So the key question is how one's reader handles block length).
 
 
According to the specification,<ref>{{cite web|url=http://www.sdcard.org/about/memory_card/pls/ |title=Simplified Physical Layer Specification v2.00|publisher=SD Card Association Website|date=2006-09-26|accessdate=2008-07-01|page=92}}</ref> the maximum capacity of a standard SD card is defined by (BLOCKNR x BLOCK_LEN), where BLOCKNR may be (4096 x 512) and BLOCK_LEN may be up to 2048. This allows a capacity of 4 GB. The main problem is that some of the card readers only support block (aka. sector) size of 512 bytes, so >1GB non SDHC cards may cause compatibility difficulties for some users.
 
 
=== SDHC cards with greater than 32 GB capacity ===
 
 
Similarly to the above, as of version 2.00 of the specification,<ref>{{cite web|url=http://www.sdcard.org/about/memory_card/pls/ |title=Simplified Physical Layer Specification v2.00|publisher=SD Card Association Website|date=2006-09-26|accessdate=2008-07-01}}</ref> the capacity of an SDHC card is limited to 32 GB. However, while not strictly adhering to that standard, it is possible to create SDHC cards of up to 2048 GB capacity. SDHC cards have fixed sector size of 512 bytes.
 
 
== SDHC ==
 
 
[[Image:SDHC memory card - 8GB.jpeg|thumb|200px|right|8GB SDHC cards]]
 
SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard that appeared in June 2006.<ref> [http://www.dramexchange.com/WeeklyResearch/Post/1/492.aspx A look into how SDHC will affect the future Nand Flash market]. DRAMeXchange, December 2006</ref> SDHC allows standard-compliant capacities in excess of 2 GB. SDHC cards are often formatted with the [[File Allocation Table#FAT32|FAT32]] [[file system]].<ref>[http://www.sdcard.org/about/sdhc/ SDHC file system]</ref> It uses the same form factor as SD, but the SD 2.0 standard in SDHC uses a different memory addressing method (sector addressing vs byte addressing), thus theoretically reaching a maximum capacity of up to 2 TB (2048 GB<!-- 2^32 * 512 = 2048 GB plain math.. -->). However the SD Card association have artificially defined the maximum limit of SDHC capacity to 32 GB. SDHC cards only work in SDHC compatible devices, but standard SD cards work in both SD and SDHC devices. The SDHC trademark is licensed to ensure compatibility.<ref>[http://www.sandisk.com/Assets/File/pdf/retail/SDHC1.pdf What are SDHC, miniSDHC, and microSDHC?] SanDisk.com</ref>
 
 
SDHC cards have '''SD Speed Class Ratings''' defined by the SD Association. The SD Speed Class Ratings specify the following '''minimum''' write speeds based on "''the best fragmented state where no memory unit is occupied''":<ref name="SDHC_speedclass">[http://www.sdcard.org/developers/tech/speed_class/ About SD speed class] SDCard.org</ref>
 
 
* Class 2: 2 MB/s
 
* Class 4: 4 MB/s
 
* Class 6: 6 MB/s
 
 
SDHC cards will often also advertise a maximum speed (such as 133x or 150x) in addition to this minimum Speed Class Rating. See section [[#Speeds|Speeds]] above for a further explanation. One critical difference between the Speed Class and the maximum speed ratings is the ability of the host device to query the SD card for the speed class and determine the best location to store data that meets the performance required. "Maximum speed" ratings are quoted by the manufacturers but unverified by any independent evaluation process.
 
 
=== SD and SDHC compatibility issues ===
 
 
During early 2007, the simultaneous availability of 4 GB SD cards compliant with later revisions of version 1.x of the SD specification but incompatible with readers based on earlier revisions of the specification, and of 4 GB SDHC cards, and incompatibilities between SD and SDHC caused confusion among consumers buying memory devices.
 
 
SD and SDHC cards and devices have these compatibility issues :
 
 
* Devices that do not specifically support SDHC do not recognize SDHC memory cards.
 
* Some manufacturers have produced 4 GB SD cards that conform to neither the SD2.0/SDHC spec nor existing SD devices.<ref>[http://techgage.com/article/sd_card_roundup Techgage review], including an OCZ 4 GBan OCZ 4 GB SD (non-SDHC) card</ref>
 
* File System: SD cards are typically formatted with the FAT16 file system, while SDHC cards are typically formatted as FAT32.<ref>http://www.sandisk.com/Assets/File/pdf/retail/SDHC1.pdf</ref> However, both types of cards can support other general-purpose filesystems, such as [[Unix File System|UFS2]]/[[ext2]] or the [[Proprietary format|proprietary]] [[exFAT]] for example.
 
 
As of mid 2008, most sold SD cards are of the SDHC variant with a capacity of 4GB, although you can find 8GB or 16GB or bigger on the market.
 
 
== SDIO ==
 
 
[[Image:HP PhotoSmart SDIO Kamera.jpg|thumb|A camera that uses the SDIO interface to connect to some HP iPAQ devices.
 
]]
 
 
SDIO stands for Secure Digital Input Output.
 
 
SD slots can actually be used for more than flash memory cards. Devices that support '''SDIO''' (typically PDAs like the [[Palm Treo]], but occasionally laptops or cell phones) can use small devices designed for the SD form factor, like [[GPS]] receivers, [[Wi-Fi]] or [[Bluetooth]] adapters, [[modem]]s, [[Ethernet]] adapters, [[barcode reader]]s, [[Infrared Data Association|IrDA]] adapters, [[FM radio]] tuners, TV tuners, [[RFID]] readers, [[digital camera]]s, or other mass storage media such as hard drives.
 
 
A number of other devices have been proposed but not yet implemented, including [[RS-232]] serial adapters, fingerprint scanners, SDIO to USB host/slave adapters (which would allow an SDIO-equipped handheld device to use USB peripherals and/or interface to PCs), magnetic strip readers, combination [[Bluetooth]]/[[Wi-Fi]]/[[GPS]] transceivers, cellular modems ([[Personal Communications Service|PCS]], [[Cellular digital packet data|CDPD]], [[Global System for Mobile Communications|GSM]], etc.), and [[Automatic Position Reporting System|APRS]]/[[TNC]] adapters.
 
 
SDIO cards are fully compatible with SD Memory Card host controller (including mechanical, electrical, power, signaling and software). When an SDIO card is inserted into a non SDIO-aware host, it will cause no physical damage or disruption to device or host controller. [[Serial Peripheral Interface Bus|SPI]] bus topology is mandatory for SDIO, unlike SD Memory. Most of the SD Memory commands are not supported in SDIO. SDIO cards can contain 8 separate logical cards, though at the moment this is at most a memory and IO function. SD slots will only take SD cards. SDIO slots will take SD cards and SDIO cards.
 
 
== SD cards with extra features ==
 
 
Various manufacturers have tried to make their SD cards stand out from the crowd in different ways
 
 
* '''SD Plus''' is a type of SD card made by Sandisk that has an integrated USB connector so it can be plugged directly into a USB port without needing any special card reader.<ref>http://www.theregister.co.uk/2005/07/25/review_sandisk_ultra_ii_sd_plus/</ref> This concept has proven successful and other companies started introducing similar designs branded as ''duo SD''.
 
 
* '''Capacity Display''' in 2006 [[A-DATA]] announced an SD card with its own digital display that would show how much free space is left on the card. <ref>[http://www.i4u.com/article7106.html I4U News - A DATA Announces SD Card w/ Bi-stable Capacity Display<!-- Bot generated title -->]</ref>
 
 
* '''[[Eye-Fi]]''', Inc. produces an SD card with [[Wi-Fi]] capability built in for 802.11g, 802.11b and backwards-compatible 802.11n wireless networks and supporting static WEP 40/104/128, WPA-PSK, WPA2-PSK security standards. The card works with any digital camera with an SD slot and can send captured images directly to a Windows PC or Apple computer wirelessly, where they can be automatically uploaded to web sites such as Flickr.com. When not in range of a wireless network connection, the card makes use of its 2GB capacity (EYE-FI-2GB model) until the images can be transferred. <ref>[http://www.eye.fi Eye-Fi » Home<!-- Bot generated title -->]</ref>
 
 
* [[Gruvi]] - A rare type of [[microSD]] card with extra DRM features
 
 
== Market penetration ==
 
 
[[Image:Canon hf100 with memory card.jpg|thumb|right|250px|A camcorder with a 4GB SDHC card]]
 
 
Secure Digital cards are used as storage media in these devices:
 
* Some [[Netbooks]], such as the [[Asus]] [[Eee PC]], ship with SDHC cards as a supplement to the primary storage
 
* [[Digital camera]]s for storing pictures and digital video
 
* [[Camcorder]]s for storing still images and video clips
 
* [[Personal digital assistant|PDAs]] for storing all kinds of data
 
* [[Mobile phone]]s for storing images, sound clips and other media files - These devices tend to use smaller variants such as [[MicroSD]] and [[MiniSD]]
 
* [[Digital audio player]]s
 
* Several [[game console]]s:
 
** [[Nintendo]] [[Wii]] console for storing multimedia and game save files.
 
*** [[Nintendo DSi]] console, presumably for similar purposes.
 
**** Third-party [[Nintendo DS homebrew|homebrew]] devices for [[Nintendo DS]] for storing games, multimedia, and game save files.
 
** Higher-end models of the [[Sony]] [[PlayStation 3]] for storing multimedia and game save files.
 
** [[GP2X]] GNU/Linux based portable games console.
 
** [[Pandora (console)]] Upcoming Linux based portable games console using the [[OMAP]] platform.
 
* [[Digital audio broadcasting]] radios
 
* [[Global Positioning System]] receivers, for storing map and waypoint data, as well as digital photos and audio.
 
* Numerous [[digital picture frame]]s
 
* [[Personal computer|PCs]] with built-in memory card readers. Such readers are usually connected internally via the [[Universal Serial Bus]] (USB).
 
* Many [[Laptop| laptop computer]]s come with an integrated SD card reader while some also read other types of cards.
 
* [[Amazon.com]]'s [[Amazon Kindle|Kindle]] handheld eBook reader to store additional files for reading.
 
* [[Panasonic]] [[plasma TV]]s have a built-in SD card reader to display images
 
* Many [[Car audio|car stereo head units]] now include an SD slot for playing [[MP3]], [[Windows Media Audio|WMA]], and other digital audio formats.
 
* Keychain-sized [[USB]]-based SD readers are available, allowing an SD (or in some cases miniSD or microSD) card to be used in the same manner as a [[USB flash drive]].
 
* [[Pleo|Pleo Robot]]s for upgrading the robot
 
* [[Ricoh Multifunctional Devices]] use DRM protected cards for postscript printing and unprotected cards for printing and scanning functionality.Also system firmware uprgrades are applied using SD cards
 
 
=== Compact digital cameras ===
 
 
SD/MMC cards have replaced [[Toshiba]]'s [[SmartMedia]] as the dominant memory card format used in ''compact'' digital cameras. In 2001 SmartMedia had achieved nearly 50% use, but by 2005 SD/MMC had achieved over 40% of the digital camera market and SmartMedia’s share had plummeted, with cards not being easily available in 2007.
 
 
A majority of the world’s leading digital camera manufacturers use SD in their product lines, including [[Casio]], [[Canon Inc.|Canon]], [[Nikon]], [[Pentax]], [[Kodak]], [[Panasonic]] and [[Konica Minolta]]. Two major brands, however, have stuck to their own proprietary formats in their cameras: [[Olympus Corporation|Olympus]] using [[XD-Picture Card|xD cards]], and [[Sony]] using [[Memory Stick]]. [[Fujifilm|Fuji]] prior to 2007 also used [[XD-Picture Card|xD cards]] exclusively, but has added SD functionality to all of their models since then.
 
 
=== Digital SLR cameras ===
 
 
SD has not conquered the market for [[DSLR|Digital SLR]] cameras. In this market [[CompactFlash]] remains the most popular format due to its historically lower price/capacity ratio, better read/write performance, and the availability of larger capacities. The larger physical size of the CompactFlash is also not an issue in the generally large SLR cameras as it may be in compact cameras.
 
 
As of 2007, however, an increasing number of models use SD/MMC/SDHC cards exclusively:
 
* Pentax
 
** [[Pentax *ist DS|*istDS]]
 
** [[Pentax K10D|K10D]] (and the Samsung GX-10)
 
** [[Pentax K100D|K100D]]
 
** [[Pentax K110D|K110D]]
 
** [[Pentax K20D|K20D]] (and the Samsung GX-20)
 
** [[Pentax K200D|K200D]]
 
* Nikon
 
** [[Nikon D50|D50]]
 
** [[Nikon D80|D80]]
 
** [[Nikon D40|D40]]
 
** [[Nikon D40x|D40X]]
 
** [[Nikon D60|D60]]
 
** [[Nikon D90|D90]]
 
* Canon
 
** [[Canon EOS 1000D|EOS 1000D]]/Rebel XS
 
** [[Canon EOS 450D|EOS 450D]]/Rebel XSi
 
 
Several high-end professional DSLRs—notably Canon's [[Canon EOS-1Ds Mark III|EOS-1Ds Mark III]] and [[Canon EOS-1D Mark III|EOS-1D Mark III]]—have two memory card slots: one CompactFlash and one SD.
 
 
=== Embedded systems ===
 
Neither SD card variant supports [[Advanced technology attachment|ATA]], limiting their use as [[solid state disk]]s unless a separate converter chip is used. Although embedded systems exist that use SD cards as their main storage mechanism, a special SD controller chip is often used.<ref>[http://www.embeddedarm.com/products/board-detail.php?product=TS-7800 TS-7800 Embedded]</ref> In September 2008, the SD Card Association announced the Embedded SD standard to be released in November.<ref>http://www.sdcard.org/press/2008_09_11_embedded_sd.pdf</ref>
 
 
A homebrew hardware [[hack]] has brought SD card support to the popular [[WRT54G]] router by utilising spare [[GPIO]] pins on the router's processor and the [[Linux kernel]]'s MMC module. Transfer speeds of 200[[KiB]]/s can be achieved with this setup.<ref>[http://against.org/mirror/kiel.kool.dk_27/ Mirror of kiel.kool.dk]</ref>
 
 
== See also ==
 
 
* [[SD Card Association]]
 
* [[P2 (storage media)|P2 card]]
 
* [[Memory Stick]]
 
 
== References ==
 
 
{{reflist|2}}
 
 
== External links ==
 
* [http://www.sdcard.org/ SD Association]
 
* [http://www.maxim-ic.com/appnotes.cfm/an_pk/3969 maxim-ic.com, Maxim Semiconductor app note describing SD with source code]
 
* [http://www.mmca.org/ mmca.org, MultiMedia Card Association]
 
* [http://www.sandisk.com/pdf/oem/ProdManualSDCardv1.9.pdf sandisk.com, SanDisk SD Card Product Manual 1.9] This is no longer available, but you can get it from [http://www.cs.ucr.edu/~amitra/sdcard/ProdManualSDCardv1.9.pdf cs.ucr.edu] (v1.9)
 
* [http://www.sandisk.com/Compatibility/ sandisk.com, SanDisk memory card device compatibility lookup]
 
* [http://www.sdcard.org/sdio/Simplified%20Physical%20Layer%20Specification.PDF sdcard.org, SD Memory Card Physical Layer Specification, version 1.01 (pdf)]
 
* [http://www.sdcard.org/about/sdio/sdio_spec sdcard.org, Simplified SDIO Card Specification]
 
* [http://www.sdcard.org/about/memory_card/pls sdcard.org, Simplified Physical Layer Specification] Useful info on the differences of SD vs. SDHC
 
* [http://www.gadgetspage.com/cameras/understanding-sd-flash-memory-card-speeds.html gadgetspage.com, Understanding SD Card Speeds]
 
* [http://www.k9spud.com/sdcard/ k9spud.com, Interfacing dsPIC30F4013 to SD Cards]
 
* [http://pinouts.ru/Memory/sdcard_pinout.shtml pinouts.ru, Secure Digital connector pinout and signals]
 
* [http://www.sdcard.org/ sdcard.org, SD Card Association]
 
* [http://www.hot-screensaver.com/2008/08/12/sandisk-extreme-iii-8gb-sdhc/ Sandisk Extreme III 8GB SDHC]
 
* [http://www.embwise.com/Sdiow.htm embwise.com, SD/SDIO Operating System independent Bus Driver]
 
* [http://www.hjreggel.net/cardspeed/index.html#special-sd.html hjreggel.net, Comparison of practically all Memory CARDS]
 
* [http://elm-chan.org/docs/mmc/mmc_e.html elm-chan.org, How to Use an MMC]
 
* [http://www.eeproductcenter.com/showArticle.jhtml?articleID=196513572 eeproductcenter.com, SD/SDHC controller for mobile devices from Cypress Semiconductor Corp]
 
 
{{Memory Cards}}
 
 
[[Category:Solid-state computer storage media]]
 
[[Category:Computer storage devices]]
 
 
[[ca:Targeta Secure Digital]]
 
[[cs:Secure Digital]]
 
[[da:Secure Digital]]
 
[[de:SD Memory Card]]
 
[[es:Secure Digital]]
 
[[fr:Carte SD]]
 
[[ko:SD 카드]]
 
[[id:Kartu Secure Digital]]
 
[[it:Secure Digital]]
 
[[he:Secure Digital]]
 
[[nl:SD-kaart]]
 
[[ja:SDメモリーカード]]
 
[[pl:Secure Digital]]
 
[[pt:Secure Digital Card]]
 
[[ru:Secure Digital]]
 
[[sk:Secure Digital]]
 
[[fi:Secure Digital]]
 
[[sv:Secure Digital]]
 
[[th:เอสดีการ์ด]]
 
[[tr:SD kart]]
 
[[uk:Secure Digital]]
 
[[zh:Secure Digital]]
 

Revision as of 18:42, 9 October 2008

kimmy is single corbin loves brittany smith cole and alexa r daten madeline is single soo any hot guys 14-16 holla at er