32 MB MultiMediaCard
|Media type||Memory card|
|Capacity||Up to 128GB (Highest currently sold)|
|Dimensions||Standard: 32 × 24 × 1.4 mm|
|Weight||Standard: ~2.0 g|
|Extended to||Secure Digital (SD)|
The MultiMediaCard (MMC) is a flash memory memory card standard. Unveiled in 1997 by SanDisk and Siemens AG, 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 × 32 mm × 1.4 mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow transfers of 4 or 8 bits at a time. It has been superseded by the Secure Digital (SD) card, but can still be used in most devices that support SD cards.
Typically, an MMC is used as a storage medium 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 available in sizes up to and including 128 GB. 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 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 device supports them.
Open standard 
This technology is a standard available to any company wanting to develop products based on it. There is no royalty charged for devices which host an MMC. A membership with the MMC Association must be purchased in order to manufacture the cards themselves.
As of July 2009, the latest specifications version 4.4 (dated March 2009) can be requested from the MMCA, and after registering downloaded free-of-charge. Older versions of the standard, as well as some optional enhancements to the standard such as MiCard and SecureMMC, must be purchased separately.
A highly detailed version is available on-line that contains essential information for writing an MMC driver.
As of 23 September 2008, the MMCA group has turned over all specifications to the JEDEC organization including embedded MMC (e-MMC) and miCARD assets. JEDEC is an organization devoted to standards for the solid-state industry.
RS-MMC and MD-MMC 
In 2004, the Reduced-Size MultiMediaCard (RS-MMC) was introduced as a smaller form factor of the MMC, about half the size: 24 mm × 18 mm × 1.4 mm. The RS-MMC uses a simple mechanical adapter to elongate the card so it can be used in any MMC (or SD) slot. RS-MMCs are currently available in sizes up to and including 2 GB.
The modern continuation of an RS-MMC is commonly know as MiniDrive (MD-MMC). A MiniDrive is generally a microSD card adapter in the RS-MMC form factor. This allows a user to take advantage of the wider range of modern MMCs available to exceed the historic 2 GB limitations of older chip technology.
The only significant hardware implementations 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. Siemens continue to use MMC for some PLC storage.
The Dual-Voltage MultimediaCard (DV-MMC) is 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 energy 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 capabilities in addition to dual-voltage support.
MMCplus and MMCmobile 
The version 4.x of the MMC standard, introduced in 2005, brought in two very significant changes to compete against SD cards: support for running at higher speeds (26 MHz and 52 MHz) than the original MMC (20 MHz) or SD (25 MHz, 50 MHz) and a four- or eight-bit-wide data bus.
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 four-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 support these features in an SD reader.
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 MMCmobile, MMCmicro supports dual voltage, is backward compatible with MMC, and can be used in full-size MMC and SD slots with a mechanical adapter. MMCmicro cards have the high-speed and four-bit-bus features of the 4.x spec but not the eight-bit bus, due to the absence of the extra pins.
It was formerly known as S-card when introduced by Samsung on December 13, 2004. It was later adapted and introduced in 2005 by the MultiMediaCard Association (MMCA) as the third form factor memory card in the MultiMediaCard family.
MMCmicro appears very similar to microSD but the two formats are not physically compatible and have incompatible pinouts.
The MiCard is a backward-compatible extension of the MMC standard with a theoretical maximum size of 2048 GB (2 TB) announced on June 2, 2007. The card is composed of two detachable parts, much like a microSD card with an SD adapter. The small memory card fits directly in a USB port while it also has MMC-compatible electrical contacts, which with an included electromechanical adapter fits in traditional MMC and SD card readers. To date, only one manufacturer has produced cards in this format.
Developed by Industrial Technology Research Institute of Taiwan, as of the announcement 12 Taiwanese companies (including A-DATA Technology, Asustek, BenQ, Carry Computer Eng. Co., C-One Technology, DBTel, Power Digital Card Co., and RiCHIP) had signed on to manufacture the new memory card. However, as of June 2011 none of the listed companies has released any such cards, and nor have any further announcements been made about plans for the format.
The card was announced to be available starting in the third quarter of 2007. It was expected to save the 12 Taiwanese companies who plan to manufacture the product and related hardware up to USD 40 million in licensing fees, that presumably would otherwise be paid to owners of competing flash memory formats. The initial card was to have a capacity of 8 GB, while the standard would support sizes up to 2048 GB. It was stated to have data transfer speeds of 480 Mbit/s (60 Mbyte/s), with plans to increase data throughput over time.
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.
Seagate, Hitachi and others are in the process of releasing SFF Hard Disk drives with an interface called CE-ATA. This interface is electrically and physically compatible with MMC specification. However, the command structure has been expanded to allow the host controller to issue ATA commands to control the hard disk drive.
|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||2.1 mm (most)
1.4 mm (rare)
|1.4 mm||1 mm|
|SPI bus mode||Optional||Optional||Optional||Yes||Yes||Yes||Yes||Yes|
|1-bit bus mode||Yes||Yes||Yes||Yes||Yes||Yes||Yes||Yes|
|4-bit bus mode||No||No||Yes||No||Optional||Optional||Optional||Optional|
|8-bit bus mode||No||No||Yes||No||No||No||No||No|
|Max clock rate||20 MHz||20 MHz||52 MHz||20 MHz?||50 MHz||208 MHz||208 MHz||208 MHz|
|Max transfer rate||20 Mbit/s||20 Mbit/s||416 Mbit/s||20 Mbit/s?||200 Mbit/s||832 Mbit/s||832 Mbit/s||832 Mbit/s|
|Max SPI transfer||20 Mbit/s||20 Mbit/s||52 Mbit/s||20 Mbit/s||50 Mbit/s||25 Mbit/s||50 Mbit/s||50 Mbit/s|
|Simplified spec||Yes||Yes||No||Not yet?||Yes||Yes||No||No|
|Membership cost||JEDEC: US$4,400/yr, optional||SD Card Association: US$2,000/year, general; US$4,500/year, executive|
|Specification cost||Free||?||Simplified spec: Free. Full spec: Free to members, US$1,000/year to R&D non-members|
|Host license||No||No||No||No||Yes, US$1,000/year. No, if using SPI-mode only.|
|Card royalties||Yes||Yes||Yes||Yes||Yes, US$1,000/year||Yes||Yes||Yes|
|Open source compatible||Yes||Yes||Yes?||Yes?||Yes||Yes||Yes||Yes|
|3.3 V||1.8 V/3.3 V||1.8 V/3.3 V||1.8 V/3.3 V||3.3 V||3.3 V (SDSC),
1.8/3.3 V (SDHC),
1.8/3.3 V (SDXC)
|3.3 V (miniSD),
1.8/3.3 V (miniSDHC)
|3.3 V (SDSC),
1.8/3.3 V (microSDHC),
1.8/3.3 V (microSDXC)
|128 GB||2 GB||128 GB?||128 GB?||?||4 GB (SD),
32 GB (SDHC),
256 GB (SDXC)
|4 GB (miniSD),
16 GB (miniSDHC)
|4 GB (microSD),
32 GB (microSDHC),
128 GB (microSDXC)
- Table data compiled from MMC, SD, and SDIO specifications from SD Association and JEDEC web sites. Data for other card variations are interpolated.
See also 
- Samsung MMC Datasheet, http://www.alldatasheet.com 2012
- Samsung's MMCmicro description, http://www.samsung.com 2007
- allmemorycards.com, MMCmicro. Extracted April 22nd, 2006.
- "Pretec Announces S-Diamond, 1st In the World to Implement miCARD Standard". Retrieved 21 January 2010.
- IHS news article, http://electronics.ihs.com 2009
- JEDEC MMC 4.4 Standard Pg.7, http://www.jedec.org 2008
- Transcend v4.0 card does not support 1.8V, http://www.transcendusa.com 2009
|Wikimedia Commons has media related to: Multi Media Card|
- Embedded MMC (eMMC) Standard MMCA 4.4 (JESD84-A44)(March 2009) (login required)
- MMCplus 13 Pin Full Size MultiMediaCard (MMC) Outline (MO-277A) (login required)
- MMCmobile 13 Pin Reduced Size MultiMediaCard (MMC) Outline (MO-278A) (login required)
- MMCmicro 10 Pin Micro Size MultiMediaCard (MMC) Outline (MO-279A) (login required)
- Sandisk OEM Manual for MMC and RS-MMC (PDF)
- KingMax MMC technical document (PDF)
- MMC pinout (tech.)
- MMCplus pinout (tech.)