From Wikipedia, the free encyclopedia

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (November 2007)

MultiMediaCard
A 32 MB MultiMediaCard
Developed by:	Siemens AG and SanDisk

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 1.4 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 They have been more or less superseded by Secure Digital cards (SD card), but still see significant use because MMCs can be used in most devices which support SD cards and they are cheaper than SD cards^{[citation needed]}.

Typically, an MMC 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 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 additionally read MMCs if the operating system drivers support them.

MMCs are currently available in sizes up to and including 4 GB with 8 GB models announced but not yet available. They 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 and SDIO (Secure Digital Input/Output) slot few companies build MMC slots into their devices (an exception is some mobile devices like the Nokia 9300 communicator, where the smaller size of the MMC is a benefit), but the slightly thinner, pin-compatible MMCs can be used in almost any device that supports SD cards if the software/firmware on the devices support them.

Contents 1 Open standard 2 Reduced-Size MultiMediaCard (RS-MMC) 3 Dual-Voltage MultimediaCard (DV-MMC) 4 MMCplus and MMCmobile 5 MMCmicro 6 SecureMMC 7 Comparisons 8 See also 9 External links 10 References

This technology is a standard available to any company wanting to develop products based on it. The specification is not free - it must be purchased from the MMC Association^[1] who impose considerable restrictions on how the specification can be used^[2].

Samsung , a major backer of MMC, provides a highly detailed datasheet^[3] which contains much of the essential information for writing an MMC driver.

MMCs also come in a smaller form factor, of about half the size: 24 mm × 18 mm × 1.4 mm. This alternate form factor is known as Reduced-Size MultiMediaCard, or RS-MMC, and was introduced in 2004. RS-MMCs are simply smaller MMCs; by using a simple mechanical adapter to elongate the card, an RS-MMC can be used in any MMC (or SD) slot. RS-MMCs are currently available in sizes up to and including 2 GB. 4 GB models have been announced but are not yet available.

The only significant hardware licensors of RS-MMCs were Nokia and Siemens, who used to use RS-MMC in their Series 60 Symbian smartphones, the Nokia 770 Internet Tablet , and generations 65 and 75 (Siemens). However, since 2006 all of Nokia's new devices with card slots have used miniSD or microSD cards, with the company appearing to abandon the MMC standard in its products. Siemens exited the mobile phone business completely in 2006.

One of the first substantial changes in MMC was the introduction of dual-voltage cards that support operations at 1.8 V in addition to 3.3 V. Running at lower voltages reduces the card's power consumption, which is important in mobile devices. However, simple dual-voltage parts quickly went out of production in favour of MMCplus and MMCmobile which offer additional capabilities on top of dual-voltage support.

The version 4.x of the MMC standard, introduced in 2005, brought in two very significant changes to compete against SD cards. These were support for running at higher speeds (26MHz, 52MHz) than the original MMC (20MHz) or SD (25MHz, 50MHz) and 4 or 8 bit wide data buses.

Version 4.x full-size cards and reduced-size cards can be marketed as MMCplus and MMCmobile respectively.

Version 4.x cards are fully backward compatible with existing readers but require updated hardware/software to use their new capabilities; even though the 4 bit wide bus and high-speed modes of operation are deliberately electrically compatible with SD, the initialization protocol is different, so firmware/software updates are required to allow these features to be enabled when the card is used in an SD reader.

MMCmicro is a micro-size version of MMC. With dimensions of 14 mm × 12 mm × 1.1 mm, it i

An additional, optional, part of the MMC 4.x specification is a DRM mechanism intended to enable MMC to compete with SD or Memory Stick in this area. Very little information is known about how SecureMMC works or how its DRM characteristics compare with its competitors.

Technical comparison

Type	MMC	RS-MMC	MMC Plus	SecureMMC	SD	SDIO	miniSD	microSD
SD Socket	Yes	Mechanical adapter	Yes	Yes	Yes	Yes	Electro-mechanical adapter	Electro-mechanical adapter
Pins	7	7	13	7	9	9	11	8
Form factor	Thin	Thin/short	Thin	Thin	Thick (exceptions possible)	Thick	Narrow/short/thin	Narrow/short/extrathin
Width	24 mm	24 mm	24 mm	24 mm	24 mm	24 mm	20 mm	11 mm
Length	32 mm	18 mm	32 mm	32 mm	32 mm	32 mm+	21.5 mm	15 mm
Thickness	1.4 mm	1.4 mm	1.4 mm	1.4 mm	2.1 mm (exceptions possible)	2.1 mm	1.4 mm	1 mm
SPI mode	Optional	Optional	Optional	Required	Required	Required	Required	Optional
1 bit mode	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
4 bit mode	No	No	Yes	?	Optional	Optional	Optional	Optional
8 bit mode	No	No	Yes	?	No	No	No	No
interrupts	No	No	No	No	No	Optional	No	No
Xfer clock	0–20 MHz	0–20 MHz	0–52 MHz	0–20 MHz?	0–25 MHz - 0–50 MHz	0–25 MHz	0–25 MHz?	0–25 MHz?
Max Transfer	20 Mbit/s	20 Mbit/s	416 Mbit/s	20 Mbit/s?	100 Mbit/s - 200 Mbit/s	100 Mbit/s	100 Mbit/s	100 Mbit/s
Max SPI Transfer	20 Mbit/s	20 Mbit/s	52 Mbit/s	20 Mbit/s	25 Mbit/s	25 Mbit/s	25 Mbit/s	25 Mbit/s
DRM	No	No	No	Yes	Yes	N/A	Yes	Yes
User encrypt	No	No	No	Yes	No	No	No	No
Simplified Spec	Yes	Yes	No	Not yet?	Yes	Yes	No	No
Memb cost	$2500/yr (not required)				$2000/yr (General), $4500/yr (Executive)
Spec cost	$500		?	?	Member	Member	Member	Member
Host license	No	No	No	No	$1000/yr + memb
Mem card royalties	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
I/O card royalties	N/A	N/A	N/A	N/A	N/A	$1000/yr+memb	N/A	N/A
Open source compatible	Yes	Yes	Yes?	Yes?	Yes	Yes	Yes	Yes
Type	MMC	RS-MMC	MMC Plus	SecureMMC	SD	SDIO	miniSD	microSD

Table data compiled mostly from simplified versions of MMC and SDIO specifications and other data on SD card and MMC association web sites. Data for other card variations is interpolated.

Capacity limit in all SD/MMC formats appears to be 128 GB in LBA mode (28-bit sector address).

• Comparison of memory cards
• Secure Digital

• MultiMediaCard Association
• Sandisk OEM Manual for MMC and RS-MMC (PDF)
• KingMax MMC technical document (PDF)
• MMC Wiki
• MMC pinout (tech.)
• MMCplus pinout (tech.)

1. ^ MMCA: Specification for Non-Members, www.mmca.org, 2007
2. ^ Product Information and License Agreement, www.mmca.org, 2007
3. ^ Samsung MMC Datasheet, http://www.samsung.com 2007

v • d • e Memory cards
CompactFlash (CF) • JEIDA • Memory Stick (MS/MS-PRO) • miCard • Microdrive (MD) • MultiMediaCard (MMC) • PC Card • Secure Digital (SD) • SmartMedia (SM) • SxS • Universal Flash Storage (UFS) • USB • xD-Picture
Comparison of memory cards • SD Card/MultiMediaCard Family Comparison