Secure Digital
An SD memory card (short for Secure Digital Memory Card, . Eng " secure digital memory card" ) is a digital storage device that works on the principle of flash storage.
The SD card was developed by SanDisk on the basis of the older MMC standard in 2001. The name of Secure Digital derived from additional hardware functions for the Digital Rights Management (DRM). Using a stored in the protected memory area the key is to prevent the illegal play protected media files the map. The encryption is done by the CPRM method of 4C consortium, which in a similar way ( CPPM ) is also used in the DVD-Audio. The exact specification is under lock and can be seen only by the paying licensees of the SD Card Association (SD Card Association ). This union has indicated that it currently 1000 members worldwide, with 460 commercial and corporate brands, the specification is, however, not yet DIN, EN, IEC or ISO standardized. Regardless, however, is part of the access logs, without access to the protected memory area, disclosed. Hardware is to handle access here via SPI.
- 6.1 speed classes
Build the map
The memory card has a built-in controller, 32 mm × 24 mm × 2.1 mm in size and had an original capacity of 8 megabytes. Subsequent models doubled the amount of space each (16, 32, ... MB ), so that capacities up to 256 gigabytes are available today. Exceptions to this scheme, 6 GB, 12 GB, 24 GB and 48 GB comprehensive cards - are only produced by Panasonic - at least in December 2010.
A small slider is located on the side of a SD card for setting the write protection. The position of this slide can be detected by a switch contact in Card Holder and evaluated by device software. When the slider is in the direction of the card contacts, signals the approval for write accesses.
The Consortium for SD cards defines only one card capacity up to 1 GB (SD 1.0 ) and 2 GB (SD 1.1). Cards with a capacity of 4 GB, as SD cards - not as SDHC cards - sold not comply with the specifications and sometimes lead, especially in older equipment problems, they also work in some SDHC devices ( for example, in some models of Panasonic Lumix ) not. Devices that only support SD 1.0 (older card reader and often newer internal notebook ), read 2GB cards sometimes, but cause several errors in the memory above 1 GB, such as typographical errors. Often the card will only appear with a capacity of 1 GB and partitioned.
In the Konsortialspezifizierung different access methods such as 1 - or 4-bit fixed serial data transmission. In addition, an initialization sequence is to be followed exactly specified otherwise, the host controller of the card reader / PDA is turned off.
Connections
To communicate with the card reader SD cards have 9 pins and microSD card 8 pins on the bottom. Assignment of the pins ( SD card):
Assignment of the pins (microSD card ):
SDHC ( SD 2.0)
An extension of this specification makes storage capacities up to 32 GB under the name SDHC ( SD High Capacity ) is possible. SDHC cards do not work with devices that can only handle SD cards. Since this is not always marked on the equipment, you should test the interaction between the card and reader before buying. The dimensions correspond to those of SD cards.
In addition, the SDHC specification defines performance classes determine the guaranteed minimum transfer rates for recording MPEG streams commit: For Class 2 card is 2 MB / s, for Class 4 is 4 MB / s, with class 6 is 6 MB / s, and class 10 is at least 10 MB / s AVCHD cameras usually need at least 1 MByte / s, the Panasonic HDC -SD1 with 13 Mbit / s, which is 1.6 MB / s, making Class 2 would be sufficient. Higher data rates are advantageous for continuous shooting of digital cameras and the transfer to the PC. According to this scheme, the classes are printed on the SDHC memory card with at least one of the numbers 2, 4, 6 or 10 within an open circle to the right ( see photos). The previous SD specifications saw such for all manufacturers generally binding standard for transfer rates not available.
In August 2006, the first 4 GB SDHC memory card came on the market in early 2008, followed by the world's first class -6 card with 32 GB, in December 2009, the Class 10 cards.
Since primarily intended for use in digital cameras, SDHC cards usually with the FAT32 file system is formatted. Therefore, they are compatible with older cameras only understand the the (usual with SD card 1.x ) FAT16 format, not compatible. For use in older cameras SDHC cards can be formatted with FAT16, but this limits the usable capacity of 2 GB and 4 GB. In principle, SD card (and thus also SDHC cards ) is not limited to the FAT file system. There is no problem with other file systems ( such as UFS, ZFS, ext3, NTFS or HFS) to use, which makes them interesting these media because of their size as a replacement for USB flash drives and for use in digital camcorders. Please note, however, is that they can not be addressed due to lack of support for these file systems in digital cameras of this and a card error.
SDHC Memory Card 8 GB Class 6
Intenso SDHC Memory Card 32GB
Contacts an SD card
Board a 64 MB SD memory card
Open the SD card ( Panasonic 16 MB)
SDXC (SD 3.0)
At the Consumer Electronics Show 2009, the SD Card Association announced the successor of SDHC. The specification of SDXC (SD eXtended Capacity) cards mentioned allows a gross size to 2 TB ( 2048 GB). The division into performance classes is retained and now extends to 104 MB / s, planned are 300 MB / s The file system is often optimized for Flash memory exFAT from Microsoft for use.
Drivers for Microsoft's exFAT there are Windows 7, Windows Vista with Service Pack 1, and Mac OS X ( 10.6.5 from ). For Windows XP, a separate update is available from service pack 2. By means of a cross-licensing agreement with Microsoft is Tuxera claims to be working to develop a exFAT drivers for embedded Linux. Whether this driver but as Tuxeras NTFS - 3G will be published after the " dual licensing " principle both under a commercial license or under an Open Source license, is unknown.
Other file systems such as FAT32 or ext3 are also possible in order to ensure compatibility with older devices. SDXC cards are limited to SDHC or SD card readers or hosts backward compatible.
Pretec has / introduced on March 6, 2009, the first SDXC memory card with a storage capacity of 32 GB and a read and write speed of 50 MB s. Panasonic introduced in the spring of 2010 cards with 48 and 64 GB on the market. The first card with a capacity of 128 GB was introduced in March 2011 by Lexar. On September 17, 2012 Lexar announced the industry's first SDXC Memory Card with a total storage capacity of 256 GB. On the German market are devices that support SDXC, available since 2010. In June 2013, PNY Technologies introduced the memory card with transfer speeds up to 100 MB / s and sizes up to 64 GB ago.
Designs
MiniSD
For small devices miniSD was developed. Is 20 mm x 21.5 mm x 1.4 mm, about half the size of the SD card. Using a frequently when purchasing supplied adapter to fit into any standard SD slot. These small cards are offered with a storage capacity up to 16 GB ( mini SDHC ). Since September 2009, production was discontinued as far as possible, thus only remaining stocks available. Owners of devices that require miniSD, however, can continue to use microSD memory cards via adapter, the continued existence of these devices is thus secured.
MicroSD
The microSD card (formerly known as TransFlash) is again smaller than the miniSD. With 11 mm × 15 mm × 1.0 mm, it has just the size of a fingernail and 2011 was the smallest flash - ROM memory map of the world. microSD cards are currently available with a storage capacity up to 128 GB ( microSDHC ).
Both miniSD and microSD ( since 2005) may bring an adapter to SD card format. A microSD card can also be brought on miniSD format also via an adapter.
Micro SD card with adapter
SD card with a USB connector and cover
SD card with USB connector without cover
SD board with two memory banks
Wi-Fi & GPS
Since mid-2008, there are SD cards with built-in WLAN function. These are now being offered by different manufacturers (Wi -Fi SD Card Transcend FlashAir ™ from Toshiba, Eye-Fi Card, etc.). Depending on the card type PC synchronization, web upload via hotspots or wireless access points are enabled, plus a saving of geographical data of the receiving site. They have the same form factor as SD cards and thus fit in most camera models. Possible Geographical coordinates taken from a database of local wireless stations ( Skyhook ) and be added to the Exif data through the Internet while guiding through the images. These cards will not work with any device.
Others
Since January 2005, there are specific SD cards that have an integrated USB port and thus can be connected without an adapter or memory card reader to a USB type A connector. The USB port is usually hidden by a cover which can be either folded or pulled off.
Transmission speed
Lag initially the transfer speed at about 3.6 MB / s (read) and 0.8 MB / s (write), so reach even cheap tickets today a write speed of up to 9MB / s The so-called high-speed cards with UHS -I interface now reach up to 80 MB / s write.
One way to increase the writing speed, is the use of two parallel- addressed memory banks.
However, the maximum values fluctuate greatly and are the manufacturer and the equipment used to use dependent. The transmission speed is usually not given directly, but as a factor based on the reading speed of CD ( = 150 kB / s for the original single speed or 1x drives). Starting from CD burners, this notation has also been established for other rewritable storage media. Example: High Speed SD Card 50x = about 7.5 MB / s write speed. It should be noted that too small a write speed of the memory card to be processed in the performance of devices with a fast, may limit high volume of data disturbing. For digital cameras, the maximum refresh sequence can be below the manufacturer's specification, the movie recording under certain circumstances the possible resolution to be limited or it may skip.
Speed classes
In the SD 3.01 specification following speed classes ( speed classes ) defined as the minimum write speeds:
On 23 June 2010, the UHS- classification was introduced for the UHS bus system (Ultra High Speed). It is the successor to the previous Normal Bus I / F (Speed Classes 2, 4 and 6) and High Speed Bus I / F (Speed Class 10). At IFA 2010, the first UHS-I SD cards were introduced and announced by the SD Association, the development of SD 4:00.
On July 16, 2013 Toshiba announced the first company to SDHC and SDXC memory cards with UHS- II interface and the updated specification 4.10. This provides up to 312 MB / s data transfer rate, the new bus system called UHS- II I / F and make new contacts on the SD memory card necessary. Nevertheless, the new standard both upward - and downward compatible. However, currently (as of November 2013) are neither card reader still cameras for SD memory cards with UHS- II interface available, which limits the speed to the level of UHS-I models.
Average access time
The average access time is the time required by the SD card, in order to find a particular memory area for reading or writing. For modern systems, a value of less than 12 ms ( 0.012 s ) is recommended. For the read access is given in almost all SD cards on writes, it may lead to higher access times. Many SD cards have when writing an average access time of about 50 ms, some are even more than 200 ms.
Maximum number of write operations
Due to the memory technology used flash memory is generally not unlimited number of times writable. However, all of the cards have an algorithm by which a substantially longer period of use can be achieved. In this case, write accesses to a logical block of the medium to changing physical memory areas deflected (English " wear leveling " ), so that for example the frequent writing of file system table does not always take place on the same memory cells and can make them early unusable. However, the methods used are not disclosed in the rule and rarely noted on the products so that there is hardly a choice for longevity. The estimated lifetime is indicated with SLC NAND chips 1,000,000 the use of MLC NAND chips 100,000 write operations. Read accesses to flash memory is unrestricted.
In addition to the limitation by write operations can of course have other defects an SD card. These include, in addition to failures caused by aging as well electrical damage ( ESD, often falls then "only" the card controller, not the flash memory itself) and mechanical damage ( damage caused by insertions, damage caused by bending of the card, the breakup of the card).
Use
SD cards are used in many different devices. Often they come for recording still pictures in digital cameras to MP3 players for playback of MP3 files and in PDAs and mobile phones for different applications to use. Mobile navigation systems use SD card to store the maps material, and also use some handheld consoles and e- book reader SD card.
Devices with SD slot are usually backward compatible with MMC cards. Thus, MMCs can usually operate in devices that are designed for the SD memory card. However, some older Toshiba laptops the operation of MMC card in the SD reader is not supported. Also, can not be addressed with full speed fast MMC cards in pure SD readers; for a full MMC support is needed. The operation of SD card in devices that are designed only for MMC, however, is not possible. To avoid incorrect uses, SD cards have a slightly thicker body than MMC cards. Therefore, normally fit SD cards because of their thickness is not in MMC slots.
Apart from the digital photography with high resolutions and fast frame rate, or recording video, is for most devices and applications do not require the use of an SD card with faster write speeds ( "high speed "). SDIO - compatible slots ( SDIO stands for " SD Input / Output" ) also allow the connection of other devices ( radio, camera, Wi-Fi ).
Counterfeit ( fake )
Especially the currently fastest and / or equipped with the greatest capacity memory cards from major brands like to be offered as an inferior, counterfeit goods. But of course any other memory cards are fake.
Nominal capacity and actual capacity
Memory card fakes show in the operating system under " Disk" - to "Properties" Although the specified (alleged ) capacity and can be even with the " quick format " option to format with the alleged capacity without a corresponding error message is displayed. However, this is only possible because in memory cards and other flash memories, the available total amount of memory (capacity) is programmed into a readable range. This storage capacity was created from the ground, since checking the capacity would take too long every time you insert the disk (imagine, for example, before, when the OS first count and check each byte of a 128GB memory card would have ). Thus, the operating system only reads out the medium stored in the memory capacity and displays the unverified to the total storage amount.
Fake memory cards can really save only a fraction of the specified amount of data but usually. In these the register in the chip (flash memory ) of the memory card is simply manipulated and usually by an additionally inserted ROL command (" rollover Left" - moving the contents of an address by 1 bit to the left ) made to the x - times (usually a factor of 8 ) of the actual capacity to the operating system to report. Thus, for example, from actual 8GB 64GB therefore, which are transmitted to the OS as available. Of course, any other capacity supposed to be reported to the operating system, can be programmed into the flash memory chip of the memory device.
When attempting to store larger amounts of data to such a manipulated card, all the more still to save files but then when the actual capacity is exhausted, simply no longer stored on the SD card, the required for this period but quite as large is as if the data were actually written to the card. Since when copying no verification of the written data takes place, but only the error flag is read, which is also manipulated in modern cards counterfeiting, appears not even a error message from the operating system by the non-working copy.
The user of a fake map, therefore, feels so long as certain until he attempts to access the stored data and these files are then either not in the file system (Index) might even be displayed can find the memory card or, but the files actually only have 0 byte size.
Write speed
As a further feature of forgery, the actual transfer rate ( read-write speed ) Fake memory cards is printed value visible far below the advertised and on the carton.
A Class 10 memory card is the way to write a minimum of 10 MB / S, as long as the interface (usually USB) and the card reader support this speed.