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<concept id="GUID-058BAEDF-5E04-5BB4-928F-0E0528FD9465" xml:lang="en"><title>MultiMediaCard

Technology</title><shortdesc>MultiMediaCard (MMC) is a low cost data storage and communication

media, and is defined by the <i>MultiMediaCard System Specification</i></shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p> The MMC specification is published by the <xref href="http://www.mmca.org" scope="external">MultiMediaCard Association</xref>. </p>

<p>Communication is based on a 7-pin serial bus designed to operate in a low

voltage range (2.0 - 3.6V). The MultiMediaCard specification defines a communication

protocol referred to as MMC mode (0-20MHz). In addition, for compatibility

with existing controllers, MultiMediaCards may offer an alternative communication

protocol which is based on the SPI standard (0-5MHz). </p>

<section id="GUID-69DA6510-AF66-566A-9B19-5554B4743D0B"><title> Omissions</title> <p>The

following features of the MultiMediaCard System Specification are not provided

in the Symbian platform MultiMediaCard controller: </p> <ul>

<li id="GUID-75439A4B-28C8-58A6-81A8-92BF08F490A1"><p>Stream read and write

operations are not supported. </p> </li>

<li id="GUID-85C665FB-152C-5A94-A245-E99D44F384C2"><p>SPI bus mode is not

supported. </p> </li>

<li id="GUID-26F8D809-57EF-5CCB-99A5-BFDCA59A5F76"><p>The MultiMediaCard System

Specification includes a feature where a MultiMediaCard can be put into a

disconnected state. This can be performed on a card which is currently in

the programming state, i.e. writing data to the disk. To place that card into

the disconnected state involves placing another card into the transfer state,

which means giving the other card the current data transfer focus. A disconnected

card will not terminate the programming operation and, if re-selected, moves

back to the programming state. The Symbian platform MultiMediaCard controller

does not support this mode of operation even if the underlying hardware interface

does. </p> </li>

</ul> </section>