Memory Card Adapters & Readers

Secure Digital (SD) is a flash (non-volatile) memory card format developed by Matsushita, SanDisk and Toshiba for use in portable devices, including digital cameras, handheld computers, PDAs and GPS units. more...

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As of 2006, SD card capacities include 8, 16, 32, 64, 128, 256, and 512 MB, 1, 2, 4, 6, 8 GB (4-32 GB: SDHC).

The format has proven to be very popular. However, compatibility issues between older devices and the newer 2GB and larger cards and the SDHC format have caused considerable confusion for consumers.

History

In August of 1999, Matsushita (best 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. 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. The new memory card format was designed to compete with Sony's Memory Stick format that was released in 1998.

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 card, to calm music industry concerns that MMC cards would allow for easy piracy of music. (A similar scheme is the MagicGate standard used in Memory Sticks.) In theory, the encryption would allow some enforcement of Digital rights management schemes on digital music, but the capability is rarely used.

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. This is why the “D” looks similar to half of an optical disc, possibly reinforced by the SD card's music industry features and consumer's familiarity with music on optical discs.

At the 2000 CES trade show Matsushita, SanDisk and Toshiba Corporation announced that a new industry-wide association will be created to set industry standards for their proprietary SD (Secure Digital) Memory Card and promote its wide acceptance in digital applications. 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. 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.

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 2.2 MB/s.

Read more at Wikipedia.org