Secure Digital - Wikipedia, the free encyclopedia. Secure Digital (SD) is a non- volatilememory card format developed by the SD Card Association (SDA) for use in portable devices. The standard was introduced in August 1. San. Disk, Panasonic (Matsushita Electric) and Toshiba as an improvement over Multi. Media. Cards (MMC). The three companies formed SD- 3. C, LLC, a company that licenses and enforces intellectual property rights associated with SD memory cards and SD host and ancillary products. The SDA uses several trademarkedlogos owned and licensed by SD- 3. C to enforce compliance with its specifications and assure users of compatibility. The four families are the original Standard- Capacity (SDSC), the High- Capacity (SDHC), the e. Xtended- Capacity (SDXC), and the SDIO, which combines input/output functions with data storage. Electrically passive adapters allow a smaller card to fit and function in a device built for a larger card. The SD card's small footprint is an ideal storage medium for smaller, thinner and more portable electronic devices. The second- generation Secure Digital (SDSC or Secure Digital Standard Capacity) card was developed. Secure Digital changed the MMC design in several ways: Asymmetrical slots in the sides of the SD card prevent inserting it upside down (while an MMC goes in most of the way but makes no contact if inverted). Most SD cards are 2. 6 data recovery tools for SD cards, USB drives and more Have a damaged USB thumb drive or memory card? These applications can help you save your data. MMCs. The SD specification defines a card called Thin SD with a thickness of 1. SDA went on to define even smaller form factors. The card's electrical contacts are recessed beneath the surface of the card, protecting them from contact with a user's fingers. The SD specification envisioned capacities and transfer rates exceeding those of MMC, and both of these functionalities have grown over time. For a comparison table, see below. Linear's IP cameras include. 3MP resolution, 20 FPS maximum, WDR, 2048(H) x 1536(V), low light, ONVIF compliant, motion detection, day/night IR cut filter, audio, SD card slot. When a micro SD card is not recognized by digital camera, mobile phone or computer, you can run memory card recovery program to restore files on the micro SD card.
While MMC uses a single pin for data transfers, the SD card added a four- wire bus mode for higher data rates. The SD card added Content Protection for Recordable Media (CPRM) security circuitry for digital rights management (DRM) content- protection. Full- size SD cards do not fit into the slimmer MMC slots, and other issues also affect the ability to use one format in a host device designed for the other. The Secure Digital High Capacity (SDHC) format, announced in January 2. SD specification, supports cards with capacities up to 3. GB. The major compatibility issues between SDHC and SDSC cards are the redefinition of the Card- Specific Data (CSD) register in version 2. SDHC cards are shipped preformatted with the FAT3. Version 2. 0 also introduces a High- speed bus mode for both SDSC and SDHC cards, which doubles the original Standard Speed clock to produce 2. MB/s. SDXC adopts Microsoft's ex. FAT file system as a mandatory feature. Version 3. 0 also introduced the Ultra High Speed (UHS) bus for both SDHC and SDXC cards, with interface speeds from 5. MByte/s to 1. 04 MByte/s for four- bit UHS- I bus. Version 4. 0, introduced in June 2. MByte/s to 3. 12 MByte/s over the four- lane (two differential lanes) UHS- II bus, which requires an additional row of physical pins. Version 5. 0 was announced in February 2. CP+ 2. 01. 6, and added . Original Title: Windows 8.1 SD storage issues I just bought an Asus Transformer T100TA Tablet running Windows 8.1 and I am having issues with my MicroSD card slot. I have 2 MicroSD cards: an 8 GB. Therefore, ex. FAT- formatted SDXC cards are not a universally readable exchange medium. Windows Vista (SP1) and later. Consequently, they may not accept SDXC cards reformatted as FAT3. FAT3. 2 on smaller cards (for SDHC compatibility). Therefore, even if a file system is supported in general, it is not always possible to use alternative file systems on SDXC cards at all depending on how strictly the SDXC card specification has been implemented in the host device. This bears a risk of accidental loss of data, as a host device may treat a card with an unrecognized file system as blank or damaged and reformat the card. The SD Association provides a formatting utility for Windows and Mac OS X that checks and formats SD, SDHC, and SDXC cards. UHS- I cards declared as UHS1. SDR1. 04) also support a clock frequency of 2. MHz, which could transfer 1. MB/s. Double data rate operation at 5. MHz (DDR5. 0) is also specified in Version 3. SDHC and micro. SDXC cards labeled as UHS- I. In this mode, four bits are transferred when the clock signal rises and another four bits when it falls, transferring an entire byte on each full clock cycle, hence a 5. MB/s operation could be transferred using a 5. MHz clock. UHS- IISpecified in version 4. MB/s (full duplex) or 3. MB/s (half duplex) using an additional row of pins. Each lane is capable of transferring up to 1. MB/s. In full duplex mode, one lane is used for Transmit while the other is used for Receive. In half duplex mode both lanes are used for the same direction of data transfer allowing a double data rate at the same clock speed. In addition to enabling higher data rates, the UHS- II interface allows for lower interface power consumption, lower I/O voltage rates and lower electromagnetic interference (EMI). Cards that comply with UHS show Roman numerals 'I' or 'II' next to the SD card logo. Use of UHS- I requires that the host device command the card to drop from 3. I/O interface pins and select the four- bit transfer mode, while UHS- II requires 0. SDIO cards are only fully functional in host devices designed to support their input- output functions (typically PDAs like the Palm Treo, but occasionally laptops or mobile phones). These devices can use the SD slot to support GPS receivers, modems, barcode readers, FM radio tuners, TV tuners, RFID readers, digital cameras, and interfaces to Wi- Fi, Bluetooth, Ethernet, and Ir. DA. Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface. SDIO cards support most of the memory commands of SD cards. SDIO cards can be structured as eight logical cards, although currently, the typical way that an SDIO card uses this capability is to structure itself as one I/O card and one memory card. The SDIO and SD interfaces are mechanically and electrically identical. Host devices built for SDIO cards generally accept SD memory cards without I/O functions. However, the reverse is not true, because host devices need suitable drivers and applications to support the card's I/O functions. For example, an HP SDIO camera usually does not work with PDAs that do not list it as an accessory. Inserting an SDIO card into any SD slot causes no physical damage nor disruption to the host device, but users may be frustrated that the SDIO card does not function fully when inserted into a seemingly compatible slot. The sequential performance aspect is the most relevant for storing and retrieving large files (relative to block sizes internal to the flash memory), such as images and multimedia. Small data (such as file names, sizes and timestamps) falls under the much lower speed limit of random access, which can be the limiting factor in some use cases. This was superseded by the Speed Class Rating, which guarantees a minimum rate at which data can be written to the card. Whatever the bus rate, the card can signal to the host that it is . Compliance with a higher speed rating is a guarantee that the card limits its use of the . Both read and write speeds must exceed the specified value. The specification defines these classes in terms of performance curves that translate into the following minimum read- write performance levels on an empty card and suitability for different applications. Class 1. 0 asserts that the card supports 1. MB/s as a minimum non- fragmented sequential write speed and uses a High Speed bus mode. The graphical symbol for the speed class has a number encircled with 'C' (C2, C4, C6, and C1. UHS- I and UHS- II cards can use UHS Speed Class rating with two possible grades: class 1 for minimum read/write performance of at least 1. MB/s ('U1' symbol featuring number 1 inside 'U') and class 3 for minimum write performance of 3. MB/s ('U3' symbol featuring 3 inside 'U'), targeted at recording 4. K video. Manufacturers can also display standard speed class symbols (C2, C4, C6, and C1. UHS speed class. Video Speed Class defines a set of requirements for UHS cards to match the modern MLC NAND flash memory. The combination lets the user record HD resolution videos with tapeless camcorders while performing other functions. It is also suitable for real- time broadcasts and capturing large HD videos. The most important advice to consumers is to continue to match SD card purchases to an application's recommended speed class. Applications that require a specific speed class usually specify this in their user manuals. Basic cards transfer data at up to six times (6. The 2. 0 specification. Manufacturers may report best- case speeds and may report the card's fastest read speed, which is typically faster than the write speed. Some vendors, including Transcend and Kingston report their cards' write speed. For example, a high- definition camcorder may require a card of not less than Class 6, suffering dropouts or corrupted video if a slower card is used. Digital cameras with slow cards may take a noticeable time after taking a photograph before being ready for the next, while the camera writes the first picture. The speed class rating does not totally characterize card performance. Different cards of the same class may vary considerably while meeting class specifications. A card's speed depends on many factors, including: The frequency of soft errors that the card's controller must re- try. Write amplification: The flash controller may need to overwrite more data than requested. This has to do with performing read- modify- write operations on write blocks, freeing up (the much larger) erase blocks, while moving data around to achieve wear leveling. File fragmentation: where there is not sufficient space for a file to be recorded in a contiguous region, it is split into non- contiguous fragments.
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