<?xml version="1.0" encoding="utf-8"?>

<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

<!-- This component and the accompanying materials are made available under the terms of the License 

"Eclipse Public License v1.0" which accompanies this distribution, 

and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

<!-- Initial Contributors:

    Nokia Corporation - initial contribution.

Contributors: 

-->

<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-114A23CF-BF8B-54F5-8AF6-FEF007891884" xml:lang="en"><title>SD Controller </title><shortdesc>Describes the Secure Digital (SD) controller supported on the Symbian

platform. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The SD controller provided by the Symbian platform is based on the <xref href="http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf" scope="external">Physical Layer Simplified Specification Version 2.00</xref> from

the SD Card Association. </p>

<section id="GUID-8A734E8C-CB18-48C8-9C8F-71AA6693B782"><title>Introduction</title> <p>The

Secure Digital (SD) card protocol is implemented as a super–set of multimedia

cards on the Symbian platform. The Multi Media Card (MMC) controller also

supports the SD cards. The SD card controller functionality is very similar

to the MMC controller and hence the SD card controller is provided by a set

of SD card classes which are derived from the MMC controller classes. </p> </section>

<section id="GUID-D41588EF-12DA-5E50-8FF4-FCE13CA81409"><title>SD Card</title> <p>The

SD cards are flash based memory cards used in high capacity data storage in

handheld devices like digital cameras, mobile phones and PDAs. The SD cards

contain 9 pins and support a 4-bit data bus. SD cards are forward compatible

with MMC and hence a device with SD card support will also support MMC cards.

SD cards use star topology with dedicated command and data signals. </p> <p>There

are two versions of SD cards: the standard capacity SD card which has a memory

capacity of up to 2GB; and high capacity SD cards which have a maximum memory

capacity of up to 32GB. The SD card functionality is provided by a layered

architecture. The 3 layers are: </p> <ul>

<li id="GUID-86ED75DF-68C4-5D0A-B11F-C9B52CEEC6ED"><p>File System Layer provides

high level file operations </p> </li>

<li id="GUID-3741FA6C-6324-59CB-B460-5BF38C87C260"><p>Media Driver layer provides

an interface to the file system and enables low level file operations like

read and write to a storage area </p> </li>

<li id="GUID-2F9CA759-FCE0-57FB-B7C4-5B93D94CAEF3"><p>SD controller provides

the low level data operations </p> </li>

</ul> <p>The SD card stack is responsible for sending the command sequences

to enable the communication between the SD card and file system of the Symbian

platform. </p> </section>

<section id="GUID-D53D0828-5579-4A4B-A611-395A3CBB34E4"><title>SD Card Controller</title> <p>The <xref href="GUID-F3BD37EC-0CCB-5859-908F-215E22C9FC20.dita">File Server</xref> uses the <xref href="GUID-2F114BC9-9B5D-5989-9CF3-37A43377DC58.dita">Media Driver</xref> to access

user data from the SD cards. The Multi Media Card (MMC) Media Driver supports

the SD cards on the Symbian platform. The MMC media drivers are implemented

in <filepath>MEDMMC.PDD</filepath>. The Media Driver uses the services of

the SD controller. The SD controller is implemented as a peripheral bus controller

in <filepath>EPBUSSD.DLL </filepath> to support SD cards. The difference between

the MMC controller and the SD controller is the default partition information

and the initialization sequence used. The main functions of an SD controller

are : </p> <ul>

<li id="GUID-9F6B9620-8F40-532E-88AD-DEDDC1BD1A03"><p>Support the SD memory

card initialization protocol. </p> </li>

<li id="GUID-EAD5FB6D-8DBB-53E2-A895-13539C73F002"><p>Reading and writing

one or more blocks from/to an SD memory card. </p> </li>

<li id="GUID-022E3749-1739-58ED-B875-343B7048E4BA"><p>Support for 4-bit wide

data bus option </p> </li>

<li id="GUID-D30CAD38-3897-5899-8761-A1DEB3DBDB92"><p>Support for Erase commands

on SD cards </p> </li>

</ul> <p>The SD controller first detects the card present in the card port.

There can be more than one card port available in a device. When more than

one card is present, the controller switches between the ports to identify

them. When it detects an SD card, the SD card initialization protocol is loaded.

The initialization protocol is a sequence of commands as described in the <xref href="http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf" scope="external">SD Association</xref> specification. </p> </section>

<section id="GUID-0EA05AC0-557D-573F-B907-41752445DC60"><title>SD controller

classes</title> <fig id="GUID-F044A820-5E7E-5A99-83D5-7CA47EBABBC8">

<title>              SD controller classes            </title>

<image href="GUID-58A5C008-88B6-5C91-8BE5-E98CA5E5A438_d0e400148_href.png" placement="inline"/>

</fig> </section>

<section id="GUID-25A29720-A91E-49FA-8E60-3060F25536EA"><title>SD Stack </title><p>The SD controller is implemented through

a set of classes derived from the MMC controller. The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DMMCStack</apiname></xref> maintains

a state machine and is responsible for detecting the new cards and initializing

the necessary stack. The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDStack</apiname></xref> is

initialised when the controller detects a new SD card. The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDStack</apiname></xref> sends

the commands to acquire the cards as described in the SD topology. <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDStack::InitialiseMemoryCardSM()</apiname></xref> is used to

initialize the SD cards and <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDStack::ConfigureMemoryCardSM()</apiname></xref> is

used to configure the card. </p></section>

<section id="GUID-23D87A40-614C-4F4D-A35E-B02216097C1A"><title>TSDCard</title><p>The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>TSDCard</apiname></xref> class

provides the functions to read and write information about the card. The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>PreferredWriteGroupLength</apiname></xref> returns the Erase Sector

size of the SD card. Clients of the SD controller should use <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DMMCStack::CardP()</apiname></xref> to

get a pointer to the card object.<xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname> TSDCard::IsCard()</apiname></xref> function

is used to detect a SD card. </p></section>

<section id="GUID-9D9AE44F-1E6F-4D09-9B3E-76AB3BFC42F2"><title>Omissions</title> <p>The

Symbian platform does not support SPI mode in SD cards. </p> </section>

<section id="GUID-8B7FCAA7-3A62-4CEA-917E-27CC571E6FAF"><title>Session</title><p>The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDSession</apiname></xref> class

provides the session related functions for the SD cards. The <xref href="GUID-3DC34D4F-E693-3BF0-B5D6-DF22FCE37340.dita"><apiname>DSDSession</apiname></xref> class

creates the descriptors with command data. These commands are then sent to

the SD cards by the controller. </p></section>

</conbody><related-links>

<link href="GUID-0E5A241A-19F5-5754-B454-45747A8D80E1.dita"><linktext>SD Card Overview</linktext>

</link>

<link href="GUID-E194A923-99E7-5DC1-BB78-D050A4793A60.dita"><linktext>SD Controller

PSL Implementation</linktext></link>