<?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-1A72F75A-1930-5C32-93B7-20F4934BCFAA" xml:lang="en"><title>ROM
Paging Overview</title><shortdesc>Memory may be conserved by only loading the parts of an execute
in place (XIP) image that are required at any given time. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-3CEEAF8D-F97A-55A8-AD34-5578A149EEFB"><title>Description</title> <p>If
an XIP ROM image is stored on an XIP media such as NOR flash, it does not
have to be copied into main memory before it can be executed. If it is stored
on non-XIP media, such as NAND flash, then it must be copied into main memory
before it can be executed. The entire XIP image can run to many megabytes,
and therefore use a lot of main memory. If ROM Paging is used, then only those
sections of the XIP image which are required are loaded into memory. Additional
sections are loaded as and when they are needed, and sections which have not
been used in some time can be discarded. The overall effect is to leave more
memory available for applications. </p> <p>&lt;add links to memory mapping,
NOR NAND&gt; </p> <p>If the ROM image is in a non-XIP ROM it has to be loaded
into RAM before it can be executed. The ROM image is split into two parts: </p> <ul>
<li id="GUID-74FB13BD-87C6-5591-B522-E2853BB89B76"><p>Paged </p> </li>
<li id="GUID-E3226DFC-D8C3-5E31-A188-D9549697C210"><p>Unpaged </p> </li>
</ul> <p>The unpaged part of the ROM image is loaded by the bootloader and
it always present in RAM. The paged part of the ROM image is paged in on demand. </p> </section>
<section id="GUID-B4DB09C1-B16C-4A45-ADCF-C0A10D577CFA"><title>Using ROM Paging</title> <p>The type of paging used and the
area of memory to use first is specified in the oby and mmp files and then
built by using specific parameters in the buildrom utility. </p> </section>
</conbody><related-links>
<link href="GUID-0AFF5666-6BF9-5022-ADBC-5EFFA743B288.dita"><linktext>ROM Paging
Guide</linktext></link>
<link href="GUID-5A71755A-E67F-5007-8C55-5B8FA65B3C04.dita"><linktext>ROM file
system</linktext></link>
<link href="GUID-D6C2202C-778C-558A-97AA-649CD6DB5E87.dita"><linktext>ROFS file
system</linktext></link>
</related-links></concept>