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26 janvier 2011 3 26 /01 /janvier /2011 07:07

Secure Digital (SD) is a non-volatile memory card format developed by the SD Card Association for use in portable devices. It is widely used in digital cameras, cell phones, ebook readers, tablet computers, netbook computers, media players, GPS receivers, and video game consoles        (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

The format has proven very popular and considered the de-facto industry standard, SD technology is used by more than 400 brands across dozens of product categories and in more than 8,000 models         (Dell Studio XPS 1640 Battery)         .

SDSC (Standard-Capacity) cards, typically called SD, have an official maximum capacity of 2 GB, though commercially available up to 4 GB. SDHC(High-Capacity) cards have a maximum capacity of 32 GB, and SDXC (eXtended-Capacity) cards have a maximum capacity of 2 TB      (Dell Vostro 1710 Battery)     .

Changes to the interface of the established format have made some older host devices, that were designed for standard SD cards, unable to handle the newer SDHC and SDXC families. All SD card families have the same physical shape, which tends to cause confusion with consumers, thus the SD Card Association has been trying to educate the public Dell KM958 battery .


In 1999, SanDisk, Matsushita, and Toshiba first agreed to develop and market the SD (Secure Digital) Memory Card, which was a development of the MMC. With a physical profile of 24×32×2.1 mm3, the new card provided both DRM up to the SDMI standard, and a high memory density for the time   Dell Studio 1555 battery .

The new format was designed to compete with Sony's Memory Stick format, which was released the previous year, and featured MagicGate DRM. It was mistakenly predicted that DRM features would be widely used due to pressure from music and other media suppliers to prevent piracy     Sony VGP-BPS13 battery .

The signature SD logo was actually developed for another use entirely: it was originally used for the Super Density Disc, which was the unsuccessful Toshiba entry in the DVD format war. This is why the D resembles an optical disc  Sony VGP-BPS13/B battery .

At the 2000 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   Sony VGP-BPS13/S battery .

Early samples of the SD Card were available in the first quarter of 2000, with production quantities of 32 and 64 megabytes available 3 months later.

In April 2006, the SD Association released a detailed specification for the non-security related parts of the SD Memory Card standard  Sony VGP-BPS13A/B battery .

The organization also released specifications for the SDIO (Secure Digital Input Output) cards and the standard SD host controller. During the same year, specifications were finalized 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 17.6 Mb/s Sony VGP-BPS13B/B battery .

In January 2009, the SD Association announced the SDXC family that will support cards up to 2 TB memory size and speeds up to 300 MBytes/sec.

Design and implementation

SD cards are based on the older MultiMediaCard (MMC) format, but have a number of differences   Sony VGP-BPL9 battery :

  • 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.
  • SD cards are thicker than MMCs. SD cards generally measure 32 × 24 × 2.1 mm, but as with MMCs can be as slim as 1.4 mm if they lack a write-protect switch   Sony VGP-BPS13B/B battery ;
  • such cards, called Thin SD, are described in the SD specification, but they are non-existent or rare in the market as most devices requiring a slimmer card use the smaller versions of SD: miniSD or microSD.
  • The card's electrical contacts are recessed beneath the surface of the card, protecting them from contact with a user's fingers  Sony VGP-BPL15 battery .
  • SD cards typically have transfer rates in the range of 80–160 Mb/s, but this is subject to grow, due to recent improvements to the MMC standard.

Devices with SD slots can use the slimmer MMCs, but standard SD cards will not fit into the slimmer MMC slots   Dell Inspiron E1505 battery .

miniSD cards can be used directly in SD slots with a simple passive adapter, since the cards 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        Dell Latitude E6400 battery ,

and card readers allow SD cards to be accessed via connectivity ports such as USB, FireWire, and the parallel printer port. SD cards can also be accessed via a floppy disk drive with a FlashPath adapter.

Each SD card family are available in up to 3 physical sizes          HP Pavilion dv6000 Battery .

The SD and SDHC families are available in all 3 sizes, but the latest SDXC family is not available in the mini size.

Standard Size

  • 32 mm x 24 mm x 2.1 mm. The MMC and rare thin SD cards are 1.4mm thick       SONY VAIO VGN-FZ Battery .

Mini Size

  • miniSD, miniSDHC, miniSDIO
  • 21.5 mm x 20 mm x 1.4 mm.

Micro Size

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 without the diagonal notched corner)          SONY VAIO VGN-FZ21E Battery .

On the left side may be a write-protection notch. If this is present, the card cannot be written. If the notch is covered by a sliding write protection tab, or absent, then the card is writeable. Because the notch is detected only by the reader, the protection can be overridden if desired (and if supported by the reader)        SONY VAIO VGN-FW21E Battery .

Not all devices support write protection, which is an optional feature of the SD standard.

Some SD cards have no write-protection notch, and it is absent completely in the microSD and miniSD formats   SONY VAIO VGN-NR11S/S Battery .

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. Such media are usually permanently marked read-only by adding the notch with no tabs         SONY VAIO VGN-NR11M/S Battery .

File system

Like other flash card technologies, most SD cards ship preformatted with a file system on top of an MBR partition scheme. SD cards are typically formatted as FAT16, SDHC cards as FAT32, SDXC cards as exFAT         SONY VAIO VGN-NR11Z/S Battery .

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, and some utilities can recover deleted files, providing that they have not been overwritten         SONY VAIO VGN-NR11Z/T Battery .

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. Conversely, an SD card can contain an embedded operating system (such as a Live USB) to recover a corrupted host computer by natively booting from the flash media reader  Sony VAIO VGN-FZ21E Battery .

SD cards with 4 GB and smaller capacities can be used with many systems by being formatted with FAT16 (4 GB only possible by using 64kiB clusters, and not widely supported) or FAT32 file system (common for file systems 4GB and bigger). Cards 4GB and bigger can only be formatted with a file system that can handle these storage sizes, such as FAT32         Sony VAIO VGN-FW21E Battery .

SD cards are plain block devices and do not in any way imply any specific partition layout or file system thus partition schemes other than MBR partitioning and the FAT file systems can be used. Under Unix-like operating systems such as Linux or FreeBSD, SD cards can be formatted using, for example, the UFS, EXT3 or the ReiserFS file systems         Sony VAIO VGN-NR11S/S Battery ;

under Mac OS X, SD cards can be partitioned as GUID devices and formatted with the HFS+ file system. Under MS-Windows and some unix systems, SD cards can be formatted using the NTFS and on later versions exFAT file system. However most consumer products will expect MBR partitioning and FAT16/FAT32 filesystem      Sony VAIO VGN-NR11Z/S Battery .

Fragmentation may slow down the effective write speed but the effect is tiny compared with that of fragmentation on hard drives. Defragmentation tools may be used. However, it is unnecessary to use any disk optimization tool because on an SD card the time required to access any block is the same          Sony VAIO VGN-NR11M/S Battery .

Defragmenting an SD card will wear the card out and is not normally recommended, as the number of writes, before failure occurs, is limited (often as few as 100,000 times).

Transfer modes

At the electrical level, SD supports at least three transfer modes: one-bit SD, four-bit SD, SPI           Sony VAIO VGN-NR11Z/T Battery .

All cards must support all three modes, except for microSD where SPI is optional. The cards must also support clock frequencies of up to 25 MHz for regular cards, and 50 MHz for high-speed cards.

One-bit SD

Separate command and data channels and a proprietary transfer format        SONY VAIO VGN-FZ180E Battery .

Four-bit SD

Uses extra pins plus some reassigned pins.


Serial Peripheral Interface Bus, a simpler subset of the SD protocol for use with microcontrollers. This mode is optional on microSD cards         SONY VAIO VGN-FZ220E Battery .


The Ultra High Speed mode is found exclusively on SDXC and SDHC products. SDXC or SDHC products with the UHS-I symbol are capable of supporting data transfer speeds up to 104 MB/s. UHS-I quadruples the extant top speed of 25 MB/s   SONY VAIO VGN-FZ340E Battery .

UHS bus interfaces are backwards compatible. SDXC UHS-I and SDHC UHS-I memory cards can achieve best performance when paired with a UHS-I device and are designed to allow consumers to record HD resolution videos, plus perform other simultaneous recording functions   SONY VAIO VGN-FZ430E Battery .


Available exclusively on SDXC and SDHC products. The standard raises the data transfer speed to a theoretical maximum of 312 MB/s.

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)   SONY VAIO VGN-FZ460E Battery .

The specification is kept secret and is accessible only to licensees. This DRM has not been seen "in the wild" and few, if any, devices appear to provide support for it. DVD-Audio uses a very similar scheme known as Content Protection for Prerecorded Media (CPPM)  SONY VAIO VGN-FZ480E Battery .

If an SD card is inserted into a Windows Phone 7, it "locks the card to the phone with an automatically generated key" so that "the SD card cannot be read by another phone, device, or PC".Symbian devices, however, are some of the very few which can perform the necessary low-level format operations on locked SD cards    SONY VAIO VGN-FZ4000 Battery .

It is therefore possible to use a device such as the Nokia N8 to reformat the card for subsequent use in other devices.

Super*Talent, a manufacturer of computer memory, has created the Super Digital card. They are the same in appearance and function as regular Secure Digital cards, but they lack the CPRM code commonly found in Secure Digital cards  SONY VAIO VGN-FZ31E Battery .

Compared to other flash memory formats

Overall, SD is less open than CompactFlash or USB flash memory drives; these are open standards which can be implemented free of payment for licensing, royalties, or documentation  SONY VAIO VGN-FZ31B Battery .

(CompactFlash and USB flash drives may, however, require licensing fees for the use of 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   SONY VAIO VGN-FZ31J Battery .

All SD cards (other than microSD) 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  SONY VAIO VGN-FZ31M Battery .

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 technical information to the public        SONY VAIO VGN-FZ31Z Battery .


There are different speeds of SD card available. The official unit of measurement is the Speed Class Rating; an older unit of measurement is the × rating.

Speed Class Rating

The Speed Class Rating is the official unit of speed measurement for SD Cards, defined by the SD Association  SONY VAIO VGN-FZ38M Battery .

The Class number represents a multiple of 8 Mb/s (1 MB/s), and meets the least sustained write speeds for a card in a fragmented state. These are the ratings of some currently available cards:

  • Class 0 cards do not specify performance, which includes all legacy cards prior to class specifications SONY VGP-BPS8 Battery.
  • Class 2, 2 MB/s, slowest for SDHC cards.
  • Class 4, 4 MB/s.
  • Class 6, 6 MB/s.
  • Class 10, 10 MB/s       SONY VGP-BPS13 Battery .

Even though the class ratings are defined by a governing body, like × speed ratings, class speed ratings are quoted by the manufacturers and not verified by any independent evaluation process. In applications that require sustained write throughput, such as video recording, the device may not perform satisfactorily if the SD card's class rating falls below a particular speed  SONY VGP-BPS13/S Battery .

For example, acamcorder that is designed to record to class 6 media may suffer dropouts or corrupted video on slower media. On slower class cards, digital cameras may experience a lag of several seconds between photo-taking, whilst the camera writes the picture to the card   SONY VGP-BPS13A/B Battery .

Important differences between the Speed Class and the traditional CD-ROM drive speed measurement ("×" speed ratings) are that speed class:

  1. may be queried by the host device;
  2. defines the minimum transfer speed   SONY VGP-BPS13B/B Battery .

Since the class rating is readable by devices, they can issue a warning to the user if the inserted card's reported rating falls below the application's minimum requirement.

On 21 May 2009, Panasonic announced new class 10 SDHC cards, claiming that this new class is "part of SD Card Specification Ver.3.0"       SONY VGP-BPS13A/S Battery .

Toshiba also announced cards based on the new 3.0 spec.

On 1 June 2010, Pretec announced the new Class-16 HD-video grade SDXC 64GB card at Computex Taipei 2010   SONY VGP-BPS13AS Battery .

× rating

The × rating is equal to 1.2 Mb/s. It is derived from the standard CD-ROM drive speed of 1.2 Mb/s (approximately 150 kB/s). Basic cards transfer data up to six times (6×) the data rate of the standard CD-ROM speed (7.2 Mb/s vs 1.2 Mb/s)  Dell Inspiron 1320n Battery .

The 2.0 specification defines speeds up to 200×, but unlike the class rating system, does not mandate that ×-ratings measure the card's least sustained write-speed. So, typically, manufacturers provide ×-ratings based on maximum read/write speeds   Dell Inspiron 1464 Battery .

Furthermore, for most cards, the fastest read speed is typically swifter than its fastest write speed, leading some manufacturers to use read-speed as the ×-rating measurement. Other vendors, such as Kingston, use write-speed.

This table lists common ratings, the minimum transfer rates, and the corresponding Speed Class  Dell Inspiron 1564 Battery .

Like most memory card formats, SD is covered by numerous patents and trademarks.

Three versions of the SD specification have been set: 1.0, 1.1 and 2.0. These were originally available only after agreeing to a non-disclosure agreement (NDA) that prohibited development of an open source driver, which generated consternation in the open-source and free software communities     Dell Inspiron 1764 Battery .

However, the system was eventually reverse-engineered, and the non-DRMed sections of the memory cards could be accessed by free software drivers.

Since then, the SD Card Association (SDA) has made access to a simplified version of the specification available under a less restrictive license     Dell Studio 1450 Battery .

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        Dell Studio 1457 Battery )

and later also for physical layer, ASSD extensions, SDIO and SDIO Bluetooth Type-A specifications under a disclaimers agreement.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   Dell Latitude D610 Battery .

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    Toshiba NB100 Battery ."

For the most part, the lack of a complete, open SD specification mainly affects embedded systems and laptop systems, since desktop users generally read SD cards via USB-based card readers. 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  Toshiba Satellite M65 battery .

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  Toshiba Satellite M60 battery .

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.

Royalties for SD/SDIO licences are imposed for manufacture and sale of memory cards and host adapters  Dell Latitude D830 Battery

(USD$1,000/year plus membership at USD$1,500/year) but 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       Dell Latitude D620 Battery .

Types of MMC/SD cards

The SD card is not the only flash memory card standard ratified by the Secure Digital Card Association (SDCA). Other SD Card Association formats include miniSD, microSD (formerly known asTransFlash before ratification by the SD Card Association)   Dell Inspiron Mini 10 Battery ,

and SDHC (Secure Digital High Capacity, for capacities above 4 GB–although, there are some card readers that cannot 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       Sony VGN-FW11S Battery .

The 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). However, 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           Sony VGN-FW11M Battery .

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    Sony VGN-FW139E/H battery .

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)   Dell Latitude E5400 Battery ,

an SDIO device must be supported and equipped with drivers and applications for the host system and usually does not 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)         Dell Latitude E4200 Battery .

This behavior is often not expected by end users who typically expect that only the SD slot is required. Similar compatibility issues are sometimes seen with Bluetooth devices, although to a much lesser extent thanks to standardized Bluetooth profiles   Dell Inspiron 300M Battery .

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  Dell Vostro A840 Battery .

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          Dell Studio 1737 battery .

The underlying SPI protocol has existed for years as a standard feature on many microcontrollers. The new protocol used open collector signaling to allow multiple cards on the same bus but this actually causes problems at higher clock rates      Dell Inspiron E1505 battery .

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       Dell RM791 battery ;

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)        Dell XPS M1530 battery

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      Dell XPS M2010 battery

— 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       Acer Aspire One battery .

Standard-SD cards (non-SDHC) with greater than 1 GB capacity

The SD Card Association's current specifications define how a standard SD (non-SDHC) card with more than 1 GB and up to 4 GB capacity should be designed         Toshiba Satellite P10 Battery .

These cards should be readable in any SD 1.01 devices that take 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, the maximum capacity of a standard SD card is defined by (BLOCKNR × BLOCK_LEN), where BLOCKNR may be (4,096 × 512) and BLOCK_LEN may be up to 2,048        SONY VGN-FZ210CE Battery .

This allows a capacity of 4 GB. The main problem is that some of the card readers support only a block (or, sector) size of 512 bytes, so greater than 1 GB non-SDHC cards may cause compatibility difficulties for users of such devices.

Compatibility issues with 4 GB and larger cards

Devices that use SD cards identify the card by requesting a 128-bit identification string from the card       Dell Precision M70 Battery .

For standard-capacity SD cards, 12 of the bits are used to identify the number of memory clusters (ranging from 1 to 4,096) 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)  Toshiba Satellite L305 Battery .

In older 1.x implementations the standard capacity block was exactly 512 bytes. This gives 4,096 × 512 × 512 = 1 gigabyte of storage memory. A later revision of the 1.x standard allowed a 4-bit field to indicate 1,024 or 2,048 bytes per block instead, yielding up to 4 gigabytes of memory storage   Toshiba Satellite T4900 Battery .

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 1,024 or 2,048.

For the new SDHC (2.0) implementation, 32 bits of the identification string are used to indicate the memory size in increments of 512 bytes       Toshiba PA3399U-2BRS battery .

The SDCA currently allows only 26 of the 32 bits to be used, giving a maximum size of 32 GB. All SD cards with a capacity larger than 4 GB must use the 2.0 implementation at minimum. Two bits that were previously reserved and fixed at 0 are now used for identifying the type of card, 0: standard; 1: SDHC; 2, 3: reserved      Toshiba Satellite A200 Battery .

Non-SDHC devices are not programmed to read this code and therefore cannot correctly identify SDHC or SDXC cards.

All SDHC readers work with standard SD cards.

Many older devices will not accept the 2 or 4 GB size even though it is in the revised standard   Toshiba Satellite 1200 Battery .

The following statement is from the SD Card 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)        Toshiba Satellite M300 Battery .

Storage capacity calculations

SD cards contain a Card-Specific Data (CSD) register which holds the card's capacity, among many other things. The format changed considerably between version 1.0 (SD) and version 2.0 (SDHC, SDXC), this is the cause of the incompatibility between SD and newer cards    SONY VGP-BPS13A/Q Battery .

CSD v2.0 expanded the C_SIZE register, removed the C_SIZE_MULT register, and no longer uses READ_BL_LEN for capacity calculation.Capacity is calculated thus:

CSD Version 1.0  SONY VGP-BPS13A/Q Battery :

Capacity=(C_SIZE+1)<<(C_SIZE_MULT+2)<<READ_BL_LEN 2GiB max.

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

CSD Version 2.0  SONY VGP-BPS13B/Q Battery :


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

for SDXC       65535<=C_SIZE                        32GiB <= capacity <= 2TiB max.  SONY VGP-BPS13B/Q Battery

SDHC cards with greater than 32 GB capacity

Similarly to the above, as of version 2.00 of the specification,the capacity of an SDHC card is limited to 32 GB. However, while not strictly adhering to that standard, it is in principle possible to create SDHC-like cards of up to 2 TB capacity  SONY VGP-BPS13/Q Battery .

Some SDHC devices will accept SDXC cards with capacities greater than 32GB and recognize the full capacity, however compatibility is not guaranteed in all cases. SDHC cards have a fixed sector size of 512 bytes.


SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard which increases card's storage capacity up to 32 GBSONY VGP-BPS13/Q Battery .

SDHC cards share the same physical and electrical form factor as older (SD 1.x) cards, allowing SDHC-devices to support both newer SDHC cards and older SD-cards. To increase addressable storage, SDHC uses sector addressing instead of byte addressing as in the previous SD standard   SONY VGP-BPS21A/B Battery .

Byte addressing supported card capacities up to 4 GB, whereas sector addressing can theoretically support capacities up to 2 TB (2048 GB). The current standard limits the maximum capacity of an SDHC card to 32 GB  (it is expected that the SDHC specification will be revised in the future to allow card capacities greater than 32 GB)      SONY VGP-BPS21/S Battery .

SDHC cards will not work in devices designed to the older SD 1.x specification. The SDHC trademark is licensed to ensure compatibility.

SD and SDHC compatibility issues

The SDHC specification was completed in June 2006,but by that time, non-standard high-capacity (>1GB) SD cards (based on the older 1.x specification) were already on the market         SONY VGP-BPS21B Battery .

The two types of storage cards were not interchangeable, creating some confusion among customers. SD and SDHC cards and devices have these compatibility issues :

  • Devices that do not specifically support SDHC do not recognize SDHC memory cards. Some devices can support SDHC through a firmware upgrade        SONY VGP-BPS21A Battery .
  • SDHC devices are backward compatible with SD memory cards.
  • Some manufacturers have produced 4 GB SD cards that conform to neither the SD2.0/SDHC spec nor existing SD devices  SONY VGP-BPS21 Battery .
  • File System: SD cards are typically formatted with the FAT16 file system, while SDHC cards are typically formatted as FAT32. However, both types of cards can support other general-purpose file systems, such as UFS2, ext2 or the proprietary exFAT for example      Sony VGP-BPS21A/B Battery .
  • Microsoft Windows may need a hotfix to support accessing SDHC cards.


The Secure Digital Extended Capacity (SDXC) format was unveiled at CES 2009 (January 7–10, 2009). The maximum capacity defined for SDXC cards is 2 TB (2048 GB)       Sony VGP-BPS21/S Battery .

The older SDHC cards also have a maximum capacity of 2 TB based on the card data structures, but this is artificially limited to 32 GB by the SD 2.0 specification. The first SDXCs being released are governed by an SD 3.0 specification (which also still specifies FAT32 and thus lower capacities)         Sony VGP-BPS21B Battery ,

whereas higher capacity and faster SDXCs are expected to follow an SD 4.0 specification, which was due to be released in spring of 2010.

The maximum transfer rate of SDXCs which follow the SD 3.0 specification was announced as 832 Mbit/s (these are called UHS104speeds), with plans that the SD 4.0 specification shall increase this to 2.4 Gbit/s  Sony VGP-BPS21A Battery .

The SDcard association selected Microsoft's proprietary exFAT file system in the official SDXC specification; however, as with SD and SDHC, it is still a plain block device and thus arbitrary partitioning and other file systems can be used, such as FAT32, NTFS, ext2, UFS, etc       Sony VGP-BPS21 Battery .


On January 7, 2009, SanDisk and Sony announced the joint development of the XC variant of the competing Memory Stick format, boasting the same 2 TB maximum capacity of SDXC.

On January 8, 2009, Panasonic announced plans for production of 64 GB SDXC cards  Sony Vaio PCG-5G2L Battery .

On March 6, 2009, Pretec introduced the world's first SDXC card with a capacity of 32 GB and a read/write speed of 400 Mbit/s. At the introduction, there were no products compatible with the new memory card.

On August 3, 2009, Toshiba announced it will launch the world's first 64 GB SDXC Memory Card  with a read speed of 480 Mbit/sSony Vaio PCG-5G3L Battery .

The 64GB card (THNSU064GAA2BC) was planned to be available in the spring of 2010.  Toshiba card was available from April 13.

On January 6, 2010, Panasonic announced its first SDXC cards with 64GB and 48GB to be available in February (RP-SDW64GE1K and RP-SDW48GE1K)      Sony Vaio PCG-5J1L Battery .

On January 6, 2010, Sony announced the launch of Handycam HDR-CX55V with SDXC support.

On February 8, 2010, Canon announced the launch of the new EOS Rebel T2i Digital SLR camera, the first EOS model to support SDXC memory cards        Sony Vaio PCG-5K2L Battery .

On February 19, 2010, Panasonic launched in Japan World's first available for consumers SDXC memory cards with 64GB and 48GB (RP-SDW64GE1K and RP-SDW48GE1K) together with USB card readers compatible with SDXC format.

On February 22, 2010, SanDisk launched its 64GB SanDisk Ultra SDXC card        Sony Vaio PCG-5J2L Battery .

The first integrated SDXC card readers are available from JMicron and are expected to be used in laptops in 2010.

SDHC and SDXC compatibility issues

In the 3.0 specification, the electronic interface of SDHC and SDXC cards is the same. This means that SDHC hosts which have drivers which recognize the newly used capability bits, and have operating system software which understands the exFAT filesystem, are compatible with SDXC cards       Sony Vaio PCG-5K1L Battery .

The decision to label cards with a capacity greater than 32GB as SDXC and to use a different filesystem is due solely to the limitations in creating larger filesystems in certain versions of Microsoft Windows. Other operating systems, such as Linux, make no distinction between SDHC and SDXC cards, as long as the card contains a compatible filesystem   Sony Vaio PCG-5L1L Battery .

SDHC and SDXC cards and hosts have these compatibility issues:

  • SDHC hosts will only support the SDXC cards which use UHS104 speeds;<  SDHC hosts will not recognize the SDXC cards which use the faster (SD 4.0), final specification of SDXC.
  • SDXC hosts are backward compatible with SD and SDHC memory cards      Sony Vaio PCG-6S2L Battery .
  • The operating systems that currently support SDXC are: Linux (with a proprietary driver for the exFAT filesystem ), Microsoft Windows 7, Windows Vista SP1+, Windows XP SP2 or SP3 with KB955704,  Windows Server 2008 SP1+, Windows Server 2003 SP2 or SP3 with KB955704, Windows CE 6+, and Mac OS X Snow Leopard (Intel-based)   Sony Vaio PCG-6S3L Battery .


A SDIO (Secure Digital Input Output) card is a combination of an SD card and an I/O device. This kind of combination is increasingly found in portable electronics devices   Sony Vaio PCG-6V1L Battery .

Hosts that support SDIO (typically PDAs like the Palm Treo, but occasionally laptops or mobile phones) can use small hosts 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  Sony Vaio PCG-6W1L Battery .

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  Sony Vaio PCG-6W2L Battery ,

combinationBluetooth/Wi-Fi/GPS transceivers, cellular modems (PCS, CDPD, GSM, etc.), and APRS/TNC adapters.

SDIO cards are fully compatible with the SD Memory Card host controller (including mechanical, electrical, power, signaling, and software)      Sony Vaio PCG-6W3L Battery .

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. Most of the SD Memory commands are supported in SDIO  Sony Vaio PCG-7111L Battery .

SDIO cards can contain 8 separate logical cards, although currently, this is at most a memory and IO function. SD slots will take SD cards only. 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  Sony Vaio PCG-7112L Battery

  • SD Plus - 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. This concept has proven successful and other companies started introducing similar designs branded as duo SD or 3 Way in the case of A-DATA's microSDHC to SDHC and USB all-in-one product  Sony Vaio PCG-7113L Battery ,
  • which was available in 2008 only.
  • 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     Sony Vaio PCG-7133L Battery .
  • 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; and 128, WPA-PSK, and WPA2-PSK security standards. The card works with any digital camera with an SD slot and can transmit captured images over a wireless network Sony Vaio PCG-7Z2L Battery.
  • When not in range of a wireless network connection, the card makes use of its 2 GB capacity (EYE-FI-2 GB model) until the images can be transferred. Some models geotag their pictures.
  • Gruvi - A rare type of microSD card with extra DRM features  Sony Vaio PCG-8Y1L Battery

Pre-Loaded Content

Towards the end of 2000s many manufacturers saw the need to distinguish their SD cards from one another. One idea was to introduce pre-loaded content onto new SD cards.

SanDisk introduced their SlotMusic which enabled users to buy digital music files already loaded onto their cards Sony Vaio PCG-8Y2L Battery .

Market penetration

Secure Digital cards are ubiquitous in consumer electronic devices, and have become the dominant means of storing several gigabytes of data in a small size       Sony Vaio PCG-8Z1L Battery .

Devices such as netbooks, digital cameras, camcorders, PDAs, mobile phones, video game consoles and digital audio players as well as many others use them.

Smaller devices tend to use microSD or miniSD rather than full sized SD cards       Sony Vaio PCG-8Z2L Battery .

SD cards are not generally used in mass produced devices where only a small amount of storage is needed due to economic reasons, or where a very large amount of storage is required.

Digital cameras

SD/MMC cards have replaced Toshiba's SmartMedia as the dominant memory card format used in digital cameras  Sony VAIO PCG-5G2L Battery .

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.

At this time all the leading digital camera manufacturers use SD in their consumer product lines      Sony VAIO PCG-5G3L Battery , including Canon, Casio, Fujifilm, Kodak, Nikon, Olympus, Panasonic, Pentax, Ricoh, Samsung, andSony. Previously, Olympus and Fujifilm used xD cards exclusively, while Sony only used Memory Stick. As of January 2010, they have added SD functionality to all models released since then      Sony VAIO PCG-5J1L Battery .

Some prosumer and professional camera models continue to offer CompactFlash, either on a second card slot or as the only storage, as it has historically offered a better price/capacity ratio and faster transfer rates       Sony VAIO PCG-5K2L Battery .

Embedded systems

Unlike CompactFlash, none of the SD card variants supports ATA signaling, limiting their use as solid state drives 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        Sony VAIO PCG-5J2L Battery .

In September 2008, the SD Card Association announced the Embedded SD standard to be released in November.

A homebrew hardware hack has brought SD card support to the popular Linksys WRT54G router by utilizing spare GPIO pins on the router's processor and the Linux kernel's MMC module. Transfer speeds of 1.6 Mbit/s can be achieved with this setup  Sony VAIO PCG-5K1L Battery .

P2 (P2 is short form for "Professional Plug-In") is a professional digital video storage media format introduced by Panasonic in 2004, and especially tailored toENG applications. It features tapeless (non-linear) recording of DVCPRO, DVCPRO50, DVCPRO-HD, or AVC-Intra streams on a solid state flash memorycard       Sony VAIO PCG-5L1L Battery .

The P2 Card is essentially a RAID of SD memory cards with an LSI controller tightly packaged in a die-cast PC card (formerly PCMCIA) enclosure, so data transfer rate increases as memory capacity increases. The system includes cameras, decks as drop-in replacement for VCRs, and a special 5.25" computer drive for random access integration with NLE systems  Sony VAIO PCG-6S2L Battery .

The cards can also be used directly where a PC card slot is available, as in most notebook computers, as a normal disk drive, although a custom software driver must first be loaded.

As of early 2010, P2 cards are available in capacities of 4, 8, 16, 32GB and 64GB       Sony VAIO PCG-6S3L Battery .

At introduction, P2 cards offered low recording capacity compared to competing, videotape-based formats (a miniDV tape holds roughly 13GB of data, and an S-size HDCAM tape holds 50GB). To solve this, camcorders and decks using P2 media employ multiple card slots, with the ability to span the recording over all slots        Sony VAIO PCG-6V1L Battery .

Cards are recorded in sequence, and when a card is full, it can be swapped out while another card is recording. This limits recording time only by power supply and the available amount of cards. If a card is partially full, the deck will record only until it is full. Unlike tape, old video cannot be recorded over accidentally. Old footage must be manually deleted   Sony VAIO PCG-6W1L Battery .

P2 cards are of a ruggedized PCMCIA type with the fastest transfer speeds currently available through this format. The card also contains a processor that organises and safeguards the files and the case is developed and crafted to "military" (according to Panasonic) specifications, making P2 cards tough and reliable  Sony VAIO PCG-6W2L Battery .     .

The first pieces of equipment released by Panasonic which use the P2 format included the AJ-SPX800 (a 2/3" broadcast camcorder for ENG and EFP applictions), the studio recorder AJ-SPD850, the AJ-PCD10 offload device (basically, a five-slot PC card reader with USB interface designed to fit a 5-1/4" IT systems bay)  Sony VAIO PCG-6W3L Battery ,

and the memory cards themselves - AJ-P2C004 (4 GB) and AJ-P2C002 (2 GB). Panasonic is currently shipping a wide range of camcorders that support the P2 format, including the professional AG-HVX200 HD handheld camcorder, and the high-end, or broadcast professional shoulder-mount AG-HPX500, AJ-HPX2000, and AJ-HPX3000 camcorders  Sony VAIO PCG-7111L Battery .

Panasonic has also announced the P2-based AG-HPX170 handheld HD camcorder. The HPX170 is very similar to the HVX200and the HVX200A, the main difference being the lack of a tape drive on the 170. The latest products to feature P2 technology are the well-received  recently launched AJ-HPX2700 and AH-HPX3700 "Varicam" high end cameras   Sony VAIO PCG-7112L Battery .


  • File format: MXF
  • Maximum datarate: 800 Mbit/s
  • Available sizes: 2 GB, 4 GB, 8 GB, 16GB, 32GB, 64GB
  • Form factor: PC card (PCMCIA) type II   Sony VAIO PCG-7113L Battery

P2 Workflow

P2 is a solid state technology, and as such departs from the older method of recording video onto tape. Since the video output is saved onto a solid state P2 memory card as a file, many possibilities are opened up to change the approach to workflow  Sony VAIO PCG-7133L Battery ;

indeed, it is claimed that the workflow can be sped up and made more reliable, which in turn, reduces production costs . Since its inception, the development of this workflow, together with partners such as Avid and Apple, has matured, and has been adopted by many major production teams   Sony VAIO PCG-7Z1L Battery .

However for many in the post production field the P2 format is quite troublesome. Because no hard copy is produced from the camera, editors must rely on massive amounts of stable drive space for security. The raw files on the card are usually treated as the 'tape', and then the converted Quicktime files are treated as capture    Sony VAIO PCG-7Z2L Battery .

P2 is still seen in the production world as

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