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32 MB MMCplus card
Media type Memory card
Capacity Up to 512 GB
Developed by JEDEC
Dimensions Standard: 32 × 24 × 1.4 mm
Weight Standard: ~2.0 g
Usage Portable devices
Extended to Secure Digital (SD)

The MultiMediaCard (MMC) is a memory card standard used for solid-state storage. Unveiled in 1997 by SanDisk and Siemens AG,[1] it is based on a surface contact low pin-count serial interface using a single memory stack substrate assembly, and is therefore much smaller than earlier systems based on high pin-count parallel interfaces using traditional surface mount assembly such as CompactFlash. Both products were initially introduced using SanDisk NOR-based Flash technology. 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. MMC can be used in many devices that can use Secure Digital (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 can.

MMCs are available in sizes up to and including 512 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 SD cards, few companies build MMC slots into their devices (an exception is some mobile devices like the Nokia 9300 communicator in 2004, 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 can use SD cards if the software/firmware on the device is capable.

While few companies build MMC slots into devices today (SD cards are more common), the embedded card (eMMC) is still widely used in the industry as a primary means of integrated storage in portable devices. It provides a low-cost flash memory system with a built-in controller that can reside inside an Android or Windows phone or low-cost PC and appear to its host as a bootable device, in lieu of a more expensive form of solid-state storage, like the traditional solid-state drive.

Open standard[edit]

Top of four types of MMC cards (clockwise from left): MMC, RS-MMC, MMCplus, MMCmobile, metal extender
Bottom of the same four cards

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 with MMCA, can be 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[2] 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.

As of February 2015, the latest specifications version 5.1 can be requested from JEDEC, and after registering with JEDEC, can be 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[2] that contains essential information for writing an MMC driver.



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 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 acceptable changes in MMC was the introduction of dual-voltage cards that can operate 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 capability.

MMCplus and MMCmobile[edit]

The version 4.x of the MMC standard, introduced in 2005, brought in two very significant changes to compete against SD cards: ability to run 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 use 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 allows 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.[3]

It was formerly known as S-card when introduced by Samsung on 13 December 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.[4]

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 2 June 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.[5]

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 US$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 allow 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[citation needed] about how SecureMMC works or how its DRM characteristics compare with its competitors.


The eMMC (embedded MMC[6]) architecture puts the MMC components (flash memory plus controller) into a small ball grid array (BGA) IC package for use in circuit boards as an embedded non-volatile memory system. This is noticeably different from other versions of MMC as this is not a user-removable card, but rather a permanent attachment to the circuit board. eMMC also does not support the SPI-bus protocol.

Almost all mobile phones and tablets use this form of flash for main storage. The latest version of the eMMC standard (JESD84-B51) by JEDEC is version 5.1 released February 2015, with speeds rivaling discrete SATA-based SSDs (400 MB/s).[7]


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.


Comparison of technical features of MMC and SD card variants
Type MMC RS-MMC MMCplus MMCmobile SecureMMC SDIO SD miniSD microSD
SD-socket compatible Yes Extender Yes Extender Yes Yes Yes Adapter Adapter
Pins 7 7 13 13 7 9 9 11 8
Width 24 mm 24 mm 24 mm 24 mm 24 mm 24 mm 24 mm 20 mm 11 mm
Length 32 mm 18 mm 32 mm 18 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 1.4 mm 2.1 mm 2.1 mm (most)
1.4 mm (rare)
1.4 mm 1 mm
1-bit SPI-bus mode Optional Optional Optional Optional Yes Yes Yes Yes Yes
Max SPI bus clock 20 MHz 20 MHz 52 MHz 52 MHz 20 MHz 50 MHz 25 MHz 50 MHz 50 MHz
1-bit MMC/SD bus mode Yes Yes Yes Yes Yes Yes Yes Yes Yes
4-bit MMC/SD bus mode No No Yes Yes No Optional Yes Yes Yes
8-bit MMC bus mode No No Yes Yes No No No No No
DDR mode No No Yes Yes Unknown Unknown Unknown Unknown Unknown
Max MMC/SD bus clock 20 MHz 20 MHz 52 MHz 52 MHz 20 MHz? 50 MHz 208 MHz 208 MHz 208 MHz
Max MMC/SD transfer rate 20 Mbit/s 20 Mbit/s 832 Mbit/s 832 Mbit/s 20 Mbit/s? 200 Mbit/s 832 Mbit/s 832 Mbit/s 832 Mbit/s
Interrupts No No No No No Optional No No No
DRM support No No No No Yes N/A Yes Yes Yes
User encrypt No No No No Yes No No No No
Simplified spec. Yes Yes No No Unknown 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 Unknown Simplified: free. Full: membership, or US$1,000/year to R&D non-members
Host license No No No No No US$1,000/year, excepting SPI-mode only use
Card royalties Yes Yes Yes Yes Yes Yes, US$1,000/year Yes Yes Yes
Open-source compatible Yes Yes Unknown Unknown Unknown Yes Yes Yes Yes
Nominal voltage 3.3 V 3.3 V 3.3 V[8][9] 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 & SDXC)
3.3 V (miniSD),
1.8/3.3 V (miniSDHC)
3.3 V (SDSC),
1.8/3.3 V (microSDHC & microSDXC)
Max capacity 128 GB 2 GB 128 GB? 2 GB 128 GB?  ? 2 GB (SD),
32 GB (SDHC),
2 GB (miniSD),
16 GB (miniSDHC)
2 GB (microSD),
32 GB (microSDHC),
512 GB (microSDXC)
Type MMC RS-MMC MMCplus MMCmobile SecureMMC SDIO SD miniSD microSD
  • Table data compiled from MMC, SD, and SDIO specifications from SD Association and JEDEC web sites. Data for other card variations are interpolated.


  1. ^ Scott Mueller. Upgrading And Repairing PCs 21st Edition. Que Publishing. ISBN 978-0789750006. 
  2. ^ "MC2GH512NMCA-2SA00 datasheet(1/102 Pages) SAMSUNG | SAMSUNG MultiMediaCard". 2005-09-22. Retrieved 2013-11-13. 
  3. ^ "Samsung Semiconductor Global Official Website" (in Russian). Retrieved 2013-11-13. 
  4. ^, MMCmicro. Extracted 22 April 2006.
  5. ^ "Pretec Announces S-Diamond, 1st In the World to Implement miCARD Standard". Retrieved 21 January 2010. 
  6. ^ What is eMMC on Datalight
  7. ^ "e.MMC v5.1". JEDEC. Retrieved 2015-08-21. 
  8. ^ MMC 4.1 Specification (PDF), JEDEC, 2008, p. 7 .
  9. ^ MMC 4.0 spec does not support 1.8V (PDF), United States: Transcend, 2009 .

External links[edit]


  • JEDEC - Solid State Technology Association