|Secure Digital card|
Pair of SD cards
|Media type||Memory Card|
|Capacity||Standard SD: 8 MB to 4 GB|
SDHC: 4 GB to 32 GB (theoretical max for SDHC is 2 TB. A memory card or flash memory card is a solid-state electronic Flash memory Data storage device used with Digital )
|Developed by||SD Card Association|
|Usage||Portable devices, including digital cameras and handheld computers|
|Extended from||MultiMediaCard (MMC)|
Secure Digital (SD) is a flash (non-volatile) memory card format developed by Matsushita, SanDisk, and Toshiba for use in portable devices. The SD Card Association develops and publishes technical standards for SD Card technology and promotes the use of the technology The MultiMediaCard ( MMC) is a Flash memory Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, is Computer memory that can retain the stored information A memory card or flash memory card is a solid-state electronic Flash memory Data storage device used with Digital SanDisk Corporation ( is an American Multinational corporation which designs and markets Flash memory card products ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. Today it is widely used in digital cameras, handheld computers, PDAs, mobile phones, GPS receivers, and video game consoles. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. A mobile device (also known as cellphone device, handheld device, handheld computer, "Palmtop" or simply handheld) is a pocket-sized Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth SD card capacities range from 8 MB to 4 GB and from 4 GB to 32 GB for SDHC cards as of 2008. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on A gigabyte (derived from the SI prefix Giga-) is a unit of Information or Computer 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common
The format has proven to be very popular. However, a change in the format, while allowing capacities greater than 2 GB (SDHC), has created compatibility issues with older devices which cannot read the new format. Secure Digital ( SD) is a non-volatile Memory card format developed by Matsushita, SanDisk, and Toshiba for use in Since SDHC format cards have the same physical shape and form factor as the older format, this has caused considerable confusion for consumers.  SDHC cards require an SDHC capable device firmware, generally not found with older devices. In Computing, firmware is a computer program that is Embedded in a hardware device for example a Microcontroller.
In August of 1999, Matsushita (better known by its Panasonic brand name), SanDisk, and Toshiba first announced an agreement on a comprehensive collaboration to jointly develop, specify and widely promote a next generation secure memory card called the SD Memory Card. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) SanDisk Corporation ( is an American Multinational corporation which designs and markets Flash memory card products ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. With a physical profile of 24 mm × 32 mm × 2. 1 mm, the new card provided both an SDMI-compliant (Secure Digital Music Initiative), high-level of copyright protection and high-density memory capacity for the time. Secure Digital Music Initiative ( SDMI) was a forum formed in late 1998, composed of more than 200 IT consumer electronics security technology ISP and recording The new memory card format was designed to compete with Sony's Memory Stick format that was released in 1998. is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with Memory Stick is a removable flash Memory card format launched by Sony in October 1998, and is also used in general to describe the whole family Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar)
The “Secure” in Secure Digital comes from the card’s origin. To create the SD card, Toshiba added encryption hardware to the already-existent MMC, to calm music industry concerns that MMCs would allow for easy piracy of music. The MultiMediaCard ( MMC) is a Flash memory (A similar scheme is the MagicGate standard used in Memory Sticks. MagicGate is a copy-protection technology introduced by Sony in 1999 as part of the Secure Digital Music Initiative (SDMI Memory Stick is a removable flash Memory card format launched by Sony in October 1998, and is also used in general to describe the whole family ) In theory, the encryption would allow some enforcement of Digital rights management schemes on digital music, but the capability is rarely used. Digital rights management ( DRM) is a generic term that refers to Access control technologies used by hardware manufacturers publishers and Copyright holders
The signature “SD” logo was actually developed for another use entirely: it was originally used for “Super Density Disc”, a prototype format by Toshiba created during the development of DVD. ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is This is why the “D” looks similar to half of an optical disc, possibly reinforced by the SD card's music industry features and consumers' familiarity with music on optical discs. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA)
At the 2000 CES trade show Matsushita, SanDisk and Toshiba Corporation announced that a new industry-wide association would be created to set industry standards for their proprietary SD (Secure Digital) Memory Card and promote its wide acceptance in digital applications. The International Consumer Electronics Show (CES is a Trade show held each January in Las Vegas, Nevada, and is sponsored The new organization, named the SDAssociation (SDA), is headquartered in California and its executive membership includes some 30 world-leading high-tech companies and major content companies. The SD Card Association develops and publishes technical standards for SD Card technology and promotes the use of the technology Sampling of the SD Memory Card began in the first quarter of 2000, and production shipments commenced in the second quarter of 2000. The card was initially available in 32 and 64 megabyte capacities. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on
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 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 GB and a minimum sustained read/write speed of 2. microSD is a format for removable Flash memory cards It is derived from SanDisk TransFlash and is used mainly in mobile 2 MB/s.
SD cards are based on the older MultiMediaCard (MMC) format, but have a number of differences:
Devices with SD slots can use the thinner MMCs, but the standard SD cards will not fit into the thinner MMC slots. 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. The miniSD Card is a small Form factor removable and portable memory device intended for use in cell phones / mobile phones, digital cameras microSD is a format for removable Flash memory cards It is derived from SanDisk TransFlash and is used mainly in mobile With an active electronic adapter, SD cards can be used in CompactFlash or PC card slots. CompactFlash ( CF) is a Mass storage device format used in portable electronic devices In Computing, PC Card (originally '''PCMCIA''', or PCMCIA Card is the Form factor of a peripheral interface designed for Laptop computers Some SD cards include a USB connector for compatibility with desktop and laptop computers, and card readers allow SD cards to be accessed via connectivity ports such as USB, FireWire, and the parallel printer port. A memory card reader is a device used for communication with a Smart card or a flash Memory card. The IEEE 1394 interface is a serial bus Interface standard for high-speed communications and Isochronous real-time data transfer frequently A parallel port is a type of interface found on Computers ( personal and otherwise for connecting various peripherals SD cards can also be accessed via a floppy disk drive with a FlashPath adapter. A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased FlashPath (FlashPath Floppy Disk Adapter is a name for a series of devices produced by SmartDisk that allow a variety of Memory cards to be used in a 3
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-protect tab. Write protection is any physical mechanism that prevents modification or erasure of valuable Data on a device 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 cassettes and videotape cassette tapes or floppy disks, where the device senses the tab/notch and determines if the card is write-protected or not. The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a Magnetic tape sound Videotape is a means of recording images and sound onto Magnetic tape as opposed to movie film. Magnetic tape is a medium for Magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of Plastic. A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased
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 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.  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 DRM-encoded Windows Media files, making use of the SD format's DRM capabilities. Digital rights management ( DRM) is a generic term that refers to Access control technologies used by hardware manufacturers publishers and Copyright holders Windows Media is a Multimedia framework for media creation and distribution for Microsoft Windows. 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 ROM rather than flash memory; it is not clear if any vendors have taken this approach.
Like other flash card technologies, most SD cards ship preformatted with the FAT or FAT 32 file system. Templateinfobox filesystem whilst covering all 3 file systems please make any style changes to both at the same time Templateinfobox filesystem whilst covering all 3 file systems please make any style changes to both at the same time In Computing, a file system (often also written as filesystem) is a method for storing and organizing Computer files and the data they contain to make 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. SCANDISK or ScanDisk is a utility in MS-DOS and Microsoft Windows systems which checks and repairs File systems and bad clusters on 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.
It is worth noting that while defragmentation utilities can be run against an SD card, there is no performance advantage in doing so (but see below on data recovery). Defragmentation is a process intended to optimize access to data on a drive with spinning platters and moving heads; however, since flash memory is truly random-access (a read to an adjacent cell is no faster than a read from any other cell), there is no performance gain. Further, the flash controller abstracts the physical memory location used for a given "sector", so that the host machine doesn't really know the layout of the data. Finally, as the defragmentation process moves data around, attempting to optimize it, a small portion of the flash memory's wear life is consumed.
However, note that any file recovery tool will struggle to recover files from highly fragmented data if the File Allocation Table becomes highly corrupted.
There are different speed grades available which are measured with the same system as CD-ROMs, in multiples of 150 kB/s (1x = 150 kB/s). CD-ROM (an initialism of "Compact Disc Read-Only Memory " is a pre-pressed Compact Disc that contains data accessible to but not writable A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 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 MB/s), and high-end cards have speeds of 150x or higher. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on 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. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. The SD card specification 1. 01 allows for a maximum speed of 66x. Higher speeds of up to 150x are defined by specification 1. 1.
The following table lists some common ratings and their respective maximum transfer rates.
Like most memory card formats, SD is covered by numerous patents (e. A patent is a set of Exclusive rights granted by a State to an inventor or his assignee for a fixed period of time in exchange for a disclosure of an g. US patent 5602987) and trademarks. A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual
There are 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. A non-disclosure agreement (NDA also known as a confidentiality agreement, confidential disclosure agreement (CDA proprietary information agreement Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified The system was eventually reverse-engineered though, and the non-DRMed sections of the memory cards could be accessed by free software drivers. Reverse engineering (RE is the process of discovering the technological principles of a device object or system through analysis of its structure function and operation
These days however, the SD Card Association (SDA) has made access to a simplified version of the specification under a less-restrictive licence. The SD Card Association develops and publishes technical standards for SD Card technology and promotes the use of the technology  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).  Like the physical specification, most of the information had already been discovered before the public release and at least Linux had a fully free driver for it. Linux (commonly pronounced ˈlɪnəks 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. "
For the most part, the lack of complete, open SD specifications mainly affects embedded systems, since desktop users generally read SD cards via USB-based card readers. An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints A memory card reader is a device used for communication with a Smart card or a flash Memory card. 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. The USB mass storage device class or USB MSC or UMS is a set of computing communications protocols defined by the USB Implementers Forum that 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.
SD supports at least three transfer modes:
All memory cards must support all three modes, except for microSD where SPI is optional. A microcontroller (also MCU or µC is a functional Computer system-on-a- chip. The cards must also support clock frequencies of up to 25 MHz for regular cards, and 50 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 SDIO cards can be made without royalties and MMC host adapters do not require a royalty. Secure Digital ( SD) is a non-volatile Memory card format developed by Matsushita, SanDisk, and Toshiba for use in 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.
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). Digital rights management ( DRM) is a generic term that refers to Access control technologies used by hardware manufacturers publishers and Copyright holders Content Protection for Recordable Media and Pre-Recorded Media ( CPRM/CPPM) is a mechanism for controlling the copying moving and deletion of digital media on a host device The 4C Entity (which should be read out as "the four company entity" is a Consortium formed by IBM, Intel, Matsushita and Toshiba The Cryptomeria cipher, commonly referred to as C2, is a Proprietary Block cipher defined and licensed by the 4C Entity. 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). DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering very High-fidelity audio content on a DVD. This type of DRM is associated with SDMI, an organisation set up by the RIAA to promote such hardware-based copy protection schemes. Secure Digital Music Initiative ( SDMI) was a forum formed in late 1998, composed of more than 200 IT consumer electronics security technology ISP and recording 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. 
Overall, SD is less open than CompactFlash or USB flash memory drives, which can be implemented for free but require licensing fees for the associated logos and trademarks. CompactFlash ( CF) is a Mass storage device format used in portable electronic devices
However, SD is much more open than Memory Stick, for which no public documentation nor any documented legacy implementation is available. Memory Stick is a removable flash Memory card format launched by Sony in October 1998, and is also used in general to describe the whole family All SD cards can, at least, be accessed freely using the well-documented SPI/MMC mode.
xD cards are simply 18-pin NAND flash chips in a special package, and support the standard command set for raw NAND flash access. The xD-Picture Card is a type of flash Memory card, used mainly in Digital cameras xD originally stood for e' x' treme D igital Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed The xD-Picture Card is a type of flash Memory card, used mainly in Digital cameras xD originally stood for e' x' treme D igital 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.
The SD card is not the only flash memory card standard ratified by the Secure Digital Card Association. A memory card or flash memory card is a solid-state electronic Flash memory Data storage device used with Digital Other SD Card Association formats include miniSD, microSD (formerly known as TransFlash before ratification by the SD Card Association), and SDHC (Secure Digital High Capacity, for capacities above 2 GB - although, there are non-standard cards over 2 GB that are not SDHC). The miniSD Card is a small Form factor removable and portable memory device intended for use in cell phones / mobile phones, digital cameras microSD is a format for removable Flash memory cards It is derived from SanDisk TransFlash and is used mainly in mobile microSD is a format for removable Flash memory cards It is derived from SanDisk TransFlash and is used mainly in mobile 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.
As SD slots still support MMCs, the separately-evolved smaller MMC variants are also compatible with SD-supporting devices. Unlike 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. The miniSD Card is a small Form factor removable and portable memory device intended for use in cell phones / mobile phones, digital cameras microSD is a format for removable Flash memory cards It is derived from SanDisk TransFlash and is used mainly in mobile More information on these variants can be found in the article about the MultiMediaCard standard. The MultiMediaCard ( MMC) is a Flash memory
It is also important to note, that unlike for data storage (which typically works everywhere where 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 expect that only the SD slot is required) and is similar to compatibility problems among Bluetooth devices. Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless
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, Ritek/Ridata, and Kingmax digital appear to support SPI. Ritek Corporation is a Taiwanese consumer electronics group specializing in optical media products flash memory MP3 players OLED displays and plastics Also, MMCs may be electrically identical to SD cards but in a thinner package and with a 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 signalling to allow multiple cards on the same bus but this actually causes problems at higher clock rate. Open collector is a type of output on many integrated circuits (IC. 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 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.
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).
For the older 1. x implementations for standard capacity, a block was exactly 512 bytes. This gives 4096 x 512 x 512 = 1 gigabyte of memory. A later revision of the 1. x standard allowed a 4-bit field to indicate blocks of 1024 bytes instead, yielding 2-gigabyte memory cards. Devices designed before this change will incorrectly identify a 2-GB card as 1 GB. Some set the block size to 2048 to create an apparent 4-GB card. Others will either fail or incorrectly identify the card as a 1-GB card.
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, 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. 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. 
Many older devices will not accept the 2 GB size even though it is in the revised standard. The following statement is from the SD association specification:
In the SD Card Associations "Simplified Physical Layer Specification v2. The SD Card Association develops and publishes technical standards for SD Card technology and promotes the use of the technology 00" it is specified in:
|9||29 = 512 Bytes|
|10||210 = 1024 Bytes|
|11||211 = 2048 Bytes|
In the SD Card Associations "Simplified Physical Layer Specification v2. The SD Card Association develops and publishes technical standards for SD Card technology and promotes the use of the technology 00":
Memory capacity = (C_SIZE+1) * 512 K = (222-1+1) * 512 K = (4194304-1+1) * 512K = 2147483648 K = 2048 GB
Although the SD Card association have placed a limit in the 2. 0 standard to a maximum of 32 GByte, the card data structures have bit fields to represent up to, and including, 2 TByte. Thus, the possibility exists for a manufacturer to violate the formal standard and produce larger SDHC cards, even though such cards would not have guaranteed compatibility with all SDHC readers.
SDHC (Secure Digital High Capacity, SD 2. 0) is an extension of the SD standard that appeared in June 2006.  SDHC allows standard-compliant capacities in excess of 2 GB. SDHC cards are often formatted with the FAT32 file system, which supports partition sizes greater than 4 GB. Templateinfobox filesystem whilst covering all 3 file systems please make any style changes to both at the same time In Computing, a file system (often also written as filesystem) is a method for storing and organizing Computer files and the data they contain to make  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 2048 GB. 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. 
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":
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 above for a further explanation. One critical difference between the Speed Class 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 unofficial and have no formal evaluation process.
As of early 2007, the simultaneous availability of non-standard 4 GB SD and of standards-compliant 4 GB SDHC cards, and incompatibilities between SD and SDHC have caused confusion among consumers buying memory devices.
SD and SDHC cards and devices have these compatibility issues :
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, modems, Ethernet adapters, barcode readers, IrDA adapters, FM radio tuners, TV tuners, RFID readers, digital cameras, or other mass storage media such as hard drives. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs A barcode reader (or barcode scanner) is an electronic device for reading printed Barcodes Like a Flatbed scanner, it consists of a light source a lens The Infrared Data Association ( IrDA) defines physical specifications Communications protocol standards for the short-range exchange of Data See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that Radio-frequency identification ( RFID) is an automatic identification method relying on storing and remotely retrieving data using devices called RFID tags or Many compact digital still cameras can record Sound and moving Video as well as still Photograph.
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 (PCS, CDPD, GSM, etc. In Telecommunications, RS-232 (Recommended Standard 232 is a standard for serial binary data signals connecting between a DTE ( Data Terminal Equipment Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices creating wireless Wi-Fi (ˈwaɪfaɪ is the trade name for the popular wireless technology used Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth Personal Communications Service or PCS is the name for the 1900  MHz radio band used for Digital Mobile phone services in Cellular Digital Packet Data ( CDPD) uses unused bandwidth normally used by AMPS Mobile phones between 800 and 900 MHz to transfer data GSM ( Global System for Mobile communications: originally from Groupe Spécial Mobile) is the most popular standard for Mobile phones in the ), and 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. SPI bus topology is mandatory for SDIO, unlike SD Memory. Interface The SPI bus specifies four logic signals SCLK &mdash Serial Clock (output from master MOSI/SIMO &mdash Master Output Slave Input (output 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.
Various manufacturers have tried to make their SD cards stand out from the crowd in different ways
Secure Digital cards are used as storage media in these devices:
SD/MMC cards have replaced Toshiba's SmartMedia as the dominant memory card format used in compact digital cameras. Pleo is a robotic dinosaur designed to emulate the appearance and behavior of a week-old baby Camarasaurus. ( is a multinational conglomerate manufacturing company headquartered in Tokyo, Japan. SmartMedia is a flash Memory card standard owned by Toshiba, with capacities ranging from 0 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, Nikon, Pentax, Kodak, Panasonic and Konica Minolta. ( is a Japanese electronic devices manufacturing company founded in 1946 with its Headquarters in Tokyo. is a Japanese Multinational corporation that specializes in imaging and optical products including Cameras photocopiers and Computer printers ( also known as Nikon or Nikon Corp, is a Multinational corporation headquartered in Tokyo Japan specializing in Optics is a wholly owned division and brand name of Hoya Corporation. Eastman Kodak Company ( is an American multinational Public company which produces imaging and photographic materials and equipment is a Japanese manufacturer of office equipment Medical imaging, Graphic imaging, Optical devices and Measuring instruments The company Two major brands, however, have stuck to their own proprietary formats in their cameras: Olympus using xD cards, and Sony using Memory Stick. The xD-Picture Card is a type of flash Memory card, used mainly in Digital cameras xD originally stood for e' x' treme D igital is a multinational conglomerate corporation headquartered in Minato Tokyo, Japan, and one of the world's largest Media conglomerates with Memory Stick is a removable flash Memory card format launched by Sony in October 1998, and is also used in general to describe the whole family Fuji prior to 2007 also used xD cards exclusively, but has added SD functionality to all of their models since then. is a Japanese company known for its Photographic film and Cameras Fujifilm is the world’s largest photographic and imaging company. The xD-Picture Card is a type of flash Memory card, used mainly in Digital cameras xD originally stood for e' x' treme D igital
SD has not conquered the market for Digital SLR cameras. A digital single-lens reflex camera ( digital SLR or DSLR) is a Digital camera that uses an automatic mirror system and Pentaprism 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. CompactFlash ( CF) is a Mass storage device format used in portable electronic devices
As of 2007, however, an increasing number of models use SD/MMC/SDHC cards exclusively: Pentax's complete line since the 2004 *istDS; Nikon's 2005 D50, 2006 D40, 2006 D80, 2007 D40X, and 2008 Nikon D60; and most recently Canon's 2008 EOS 450D/Rebel XSi. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. PENTAX *ist DS is a digital SLR Camera produced by Pentax. The *ist DS produces a 6 The D50 is a now-discontinued 61 megapixel entry-level Digital single-lens reflex camera from Nikon. The D40 and the D40x are the most compact members of Nikon 's entry-level digital SLR range announced November 16, 2006. The D80 is a Digital single-lens reflex camera model announced by Nikon on August 9th 2006 The Nikon D60 is a 102 Megapixel Digital single-lens reflex camera announced in January 2008. The EOS 450D (called EOS Rebel XSi in North America and EOS Kiss X2 in Japan) is a 12
Several high-end professional DSLRs — notably Canon's EOS-1Ds Mark III and EOS-1D Mark III — support both CompactFlash and SD for greater flexibility and storage capacity. The EOS-1Ds Mark III is a digital SLR camera body by Canon Inc The EOS 1D Mark III is a professional 101 Megapixel Digital single lens reflex camera (DSLR camera body produced by Canon.