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<concept id="GUID-0E5A241A-19F5-5754-B454-45747A8D80E1" xml:lang="en"><title>SD Card

Overview</title><shortdesc>Description of SD card features available to application developers

and what a device creator must write to provide SD card support.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>SD memory cards (Secure Digital memory cards) are flash-based memory cards

designed to provide secure high capacity data storage. </p>

<p>The SD controller supports the <i>Simplified SD Physical layer specification

version 2.0</i> which is owned by the <i>SD Card Association</i> and the <i>SD

Group</i>. </p>

<p>The SD memory card standard is defined to be protocol forward compatible

with MultiMediaCard version 2.11 and it is possible for a MultiMediaCard to

be inserted into an SD memory card socket and host systems to support both

types of card. </p>

<section id="GUID-AA07DD5E-0DB7-4B0C-8475-7A36E9F600CA"><title>Purpose</title> <p>SD cards are based on MultiMediaCards (MMC)

but with additional functionality detailed below. Symbian platform support

for SD is built on top of the MMC support. This section describes the additional

functionality available to applications using SD cards. This section also

describes the additional work required to support SD cards. </p> </section>

<section id="GUID-E53DD689-D81A-44A1-870B-3ECE796B86F1"><title>Required background</title> <p>You should be familiar with

the following: </p> <ul>

<li id="GUID-390334A3-BC5D-5E90-A114-E44C724DE63B"><p><xref href="GUID-79B2CF91-FB95-5E7C-81CC-235A6A660D88.dita">MMC

Controller</xref>  </p> </li>

<li id="GUID-C1841C2F-9D08-59D4-8183-6B1179D33763"><p> <xref href="http://www.sdcard.org/developers/tech/sdcard/pls/" scope="external">SD Simplified Specification</xref>  </p> </li>

</ul> </section>

<section id="GUID-EC87FA96-C124-43A0-A173-510B8A73FE98"><title>Key concepts and terms</title> <p>An SD card is very similar

to a MultiMediaCard (MMC) but with additional features to support high capacity,

high speed, secure storage. </p> <p>As SD cards are very similar to MMC, you

should read the section on <xref href="GUID-BE6AFD38-5952-537F-848C-C76C8F5FA9BF.dita">MMC

Controller Architecture</xref> before reading the <xref href="GUID-114A23CF-BF8B-54F5-8AF6-FEF007891884.dita">SD

Controller</xref> documentation. </p> </section>

<section id="GUID-C800CBB8-057F-494B-B0B8-95C6DBE13006"><title>Architecture</title> <p>SD support is divided into two parts,

the Platform Independent Layer (PIL) and the Platform Specific Layer (PSL). </p> <p>The

PIL is implemented as an E32 peripheral bus controller - <filepath>EPBUSSD.DLL</filepath> which

is a kernel extension and extends the functionality of the matching MMC library <filepath>EPBUSM.DLL</filepath>.

The <filepath>EPBUSSD.DLL</filepath> library consists of a generic peripheral

bus layer, which is identical to the one used for MMC, and a generic SD card

layer. The SD card layer is a superset of the MMC layer and derives additional

classes for SD cards from the MMC classes. These derived classes support the

additional features found in an SD card. </p> <p>The additional functionality

available in an SD card includes: </p> <ul>

<li id="GUID-832D06C4-3EA0-552B-8002-3CB9CB281BE7"><p>an optional 4-bit wide

data bus </p> </li>

<li id="GUID-04D41D5C-B0E4-51FE-96D8-561EADE20D11"><p>individual SD card addressing </p> </li>

<li id="GUID-B1EA016E-F935-5590-9446-86B0C4825B51"><p>support for card capacities

up to 32Gb </p> </li>

<li id="GUID-741CF2BF-08A3-50C1-B3B8-DF616C9C5B28"><p>revised erase ranges

allowing smaller ranges to be erased from an SD card </p> </li>

<li id="GUID-BCEA1C92-84C5-5571-9AE0-BA7AC76B3003"><p>optional secure data

area - Symbian Platform does not provide support for using the secure data

area on an SD card. </p> </li>

</ul> <p>You, as a device creator, will need to write the PSL. Implementing

the PSL is described in <xref href="GUID-E194A923-99E7-5DC1-BB78-D050A4793A60.dita">SD

Controller PSL Implementation</xref>. </p> </section>

<section id="GUID-D43830D1-D78F-48A7-8467-4E8A52FE403B"><title>Key Classes</title> <p>The classes used for SD cards are SD

specific versions of the classes used for the MMC cards and the main SD-related

are listed here. </p> <table id="GUID-42E860FB-DF1F-5F11-93EA-DAF25C892B9D">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>Class</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDStack</apiname></xref>  </p> </entry>

<entry><p>The SD protocol stack, derived from <xref href="GUID-B5193656-9819-3E00-A335-EEF1726115A5.dita"><apiname>DMMCStack</apiname></xref>.

Uses the star topography to identify each SD card rather than the bus topography

used by MMC. Also handles individual card initialization. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-B170A819-C146-3DD2-85C2-69CC121A9023.dita"><apiname>TSDCard</apiname></xref>  </p> </entry>

<entry><p>Derived from <xref href="GUID-5B985623-6A0B-3FBB-90BD-367F25CC70E7.dita"><apiname>TMMCard</apiname></xref> but contains the erase sector

size and any special formatting requirements for the SD card. Includes information

from the SD Card Configuration Register (SCR). </p> </entry>

</row>

</tbody>

</tgroup>

</table> </section>

<section id="GUID-BFBB02C3-1710-4F52-94C9-94386F8AEA5A"><title>Typical uses</title> <p>The typical uses for the SD card classes

are the same as for MMC. </p> </section>

</conbody><related-links>

<link href="GUID-79B2CF91-FB95-5E7C-81CC-235A6A660D88.dita"><linktext>MMC Controller</linktext>

</link>

<link href="GUID-058BAEDF-5E04-5BB4-928F-0E0528FD9465.dita"><linktext>MultiMediaCard

Technology</linktext></link>

<link href="GUID-BE6AFD38-5952-537F-848C-C76C8F5FA9BF.dita"><linktext>MMC Controller

Architecture</linktext></link>

<link href="GUID-C059F39F-BC53-5C92-B05E-863B8CF22859.dita"><linktext>Command Objects</linktext>

</link>

</related-links></concept>