MultiMediaCard
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A 32 MB MultiMediaCard |
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MultiMediaCard |
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A 128 MB RS-MMC card and an adapter |
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An RS-MMC card with adapter attached |
The
MultiMediaCard (
MMC) is a
flash memory memory card standard. Unveiled in
1997 by
Siemens AG and
SanDisk, it is based on
Toshiba's
NAND-based flash memory, and is therefore much smaller than earlier systems based on
Intel NOR-based memory such as
CompactFlash. MMC is about the size of a postage stamp: 24 mm x 32 mm x 1.5 mm. MMC originally used a 1-
bit serial interface, but newer versions of the specification allow transfers of 4 or sometimes even 8 bits at a time. They have been more or less superseded by
Secure Digital cards, but still see significant use because MMC cards can be used in any device which supports SD cards.
Typically, an MMC card is used as storage media for a portable device, in a form that can easily be removed for access by a
PC. For example, a
digital camera would use an MMC card for storing image files. With an MMC reader (typically a small box that connects via
USB or some other serial connection, although some can be found integrated into the computer itself), a user could copy the pictures taken with the digital camera off to his or her computer. Modern computers, both laptops and desktops, often have SD slots, which can read MMC cards.
MMC cards are currently available in sizes up to and including 8
GB, and are used in almost every context in which
memory cards are used, like
cellular phones,
digital audio players,
digital cameras and
PDAs. Since the introduction of
Secure Digital card few companies build MMC slots into their devices, but the slightly thinner, pin-compatible MMC cards can be used in almost any device that supports SD cards.
This technology is an
open standard available to any
company who wants to improve upon it or develop products for it.
MMC cards also come in a smaller form factor, of about half the size: 24 mm × 16 mm × 1.5 mm. This alternate form factor is known as
Reduced-Size MultiMediaCard, or
RS-MMC, and was introduced in
2004. RS-MMC cards are simply smaller MMC cards; by using a simple mechanical adapter to elongate the card, an RS-MMC card can be used in any MMC (or SD) slot. RS-MMC cards are currently available in sizes up to and including 8GB.
The only significant hardware licensors of RS-MMC cards are Nokia and Siemens, who often use RS-MMC in their
Series 60 Symbian smartphones, the
Nokia 770 Internet Tablet (Nokia), and generations 65 and 75 (Siemens). Newer RS-MMC cards, used in Nokia's newer phones (like the
Nokia 6630 and
Nokia 6680), support a lower
voltage (1.8 V instead of 3 V) mode to reduce battery demand, and these lower-voltage RS-MMC cards, known as
Dual-Voltage Reduced-Size MMC (
DV RS-MMC), and can be marketed as
MMCmobile when they meet the MMC
mobile card standards. These low-voltage cards are backwards compatible with older RS-MMC devices. The dual voltage cards, and the MMC
mobile are part of the MMC 4.x standards.
MMCmini is a mini-size version of MMC. With dimensions of 20 mm × 21.5 mm × 1.4 mm, it has roughly the same size as RS-MMC. Unlike MMC and RS-MMC, MMC
mini has a 11-pin configuration and a maximum storage capacity of 2048 MB. The idea of using MMC
mini on the hardware is to also reduce the size of the memory card slot rather than only reduce the size of the memory card itself.
MMCmicro is a micro-size version of MMC. With dimensions of 14 mm × 12 mm × 1.1 mm, it is even smaller and thinner than RS-MMC. Like MMC
mobile, MMC
micro supports dual voltage, is backward compatible with MMC, and can be used in full-size MMC and SD slots with a mechanical adapter.
Standard 4.x (4.0, 4.1, etc.) was released in
2005 (MMCA System Specification 4.1). This new standard involves the higher performance MMC4 (with the same basic MMC form factor but more pins) called MMC
plus, and RS-MMC4, marketed as MMC
mobile. MMC/RS-MMC cards are generic names normally used for previous generation cards.Also in the works is
SecureMMC, which will feature encryption features similar to Secure Digital or
MagicGate Memory Sticks.
*
Secure Digital*
MultiMediaCard Association*
Sandisk OEM Manual for MMC and RS-MMC (PDF)*
KingMax MMC technical document (PDF)*
MMC Wiki*
Samsung Introduces High-Performance MMC Cards
