Hardware Reference
In-Depth Information
The MultiMediaCard (MMC) was codeveloped by SanDisk and Infineon Technologies AG (formerly
Siemens AG) in November 1997 for use with smart phones, MP3 players, digital cameras, and
camcorders. The MMC uses a simple 7-pin serial interface to devices and contains low-voltage flash
memory. The MultiMediaCard Association (
www.mmca.org
) was founded in 1998 to promote the
MMC standard and aid development of new products. In November 2002, MMCA announced the
development of the Reduced Size MultiMediaCard (RS-MMC), which reduces the size of the
standard MMC by about 40% and can be adapted for use with standard MMC devices. The first flash
memory cards in this form factor were introduced in early 2004 to support compact smartphones. In
2008, the MMCA merged with JEDEC (
www.jedec.org
), which is the global leader in developing
open standards for the microelectronics industry.
SecureDigital
A SecureDigital (SD) storage device is about the same size as an MMC (many devices can use both
types of flash memory), but it's a more sophisticated product. SD, which was codeveloped by
Toshiba, Matsushita Electric (Panasonic), and SanDisk in 1999, gets its name from two special
features. The first is encrypted storage of data for additional security, meeting current and future
Secure Digital Music Initiative (SDMI) standards for portable devices. The second is a mechanical
write-protection switch. The SD slot can also be used for adding memory to Palm PDAs. The SDIO
standard was created in January 2002 to enable SD slots to be used for small digital cameras and
other types of expansion with various brands of PDAs and other devices. The SD Card Association
(
www.sdcard.org
)
was established in 2000 to promote the SD standard and aid the development of
new products. Note that some laptop computers have built-in SD slots.
Reduced-size versions of SD include MiniSD (introduced in 2003) and MicroSD (introduced in
2005). MiniSD and MicroSD are popular choices for smartphones and can be adapted to a standard
SD slot. MicroSD is compatible with the TransFlash standard for mobile phones.
The original SD standard allowed for memory card capacities of up to 2GB. To support higher
capacities the SDHC (High Capacity) standard was created in 2006. SDHC supports cards from 4GB
to 32GB in capacity. To increase capacity beyond 32GB, the SDXC (eXtended Capacity) format was
released in 2009. SDXC supports capacities of up to 2TB. Note that devices are backward
compatible, meaning that a device that supports SDXC also supports SDHC and standard SD cards.
A device that supports SDHC also accepts standard SD cards, but such a device does not support
SDXC cards. Devices that support only standard SD do not support either SDHC or SDXC cards.
Sony Memory Stick
Sony, which is heavily involved in both laptop computers and a variety of digital cameras and
camcorder products, has its own proprietary version of flash memory known as the Sony Memory
Stick. This device features an erase-protection switch, which prevents accidental erasure of your
photographs. Sony has also licensed Memory Stick technology to other companies, such as Lexar
Media and SanDisk.
Lexar introduced the enhanced Memory Stick Pro in 2003. Memory Stick Pro includes MagicGate
encryption technology, which enables digital rights management, and Lexar's proprietary high-speed
memory controller. Memory Stick Pro is sometimes referred to as
MagicGate Memory Stick
.
The Memory Stick Pro Duo is a reduced-size, reduced-weight version of the standard Memory Stick
Pro. It can be adapted to devices designed for the Memory Stick Pro.
