Adaptation/GUID-1A72F75A-1930-5C32-93B7-20F4934BCFAA.dita
author Graeme Price <GRAEME.PRICE@NOKIA.COM>
Fri, 15 Oct 2010 14:32:18 +0100
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<?xml version="1.0" encoding="utf-8"?>
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
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<!-- This component and the accompanying materials are made available under the terms of the License 
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"Eclipse Public License v1.0" which accompanies this distribution, 
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
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<!-- Initial Contributors:
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    Nokia Corporation - initial contribution.
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Contributors: 
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-->
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<!DOCTYPE concept
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="GUID-1A72F75A-1930-5C32-93B7-20F4934BCFAA" xml:lang="en"><title>ROM
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Paging Overview</title><shortdesc>Memory may be conserved by only loading the parts of an execute
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in place (XIP) image that are required at any given time. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
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<section id="GUID-3CEEAF8D-F97A-55A8-AD34-5578A149EEFB"><title>Description</title> <p>If
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an XIP ROM image is stored on an XIP media such as NOR flash, it does not
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have to be copied into main memory before it can be executed. If it is stored
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on non-XIP media, such as NAND flash, then it must be copied into main memory
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before it can be executed. The entire XIP image can run to many megabytes,
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and therefore use a lot of main memory. If ROM Paging is used, then only those
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sections of the XIP image which are required are loaded into memory. Additional
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sections are loaded as and when they are needed, and sections which have not
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been used in some time can be discarded. The overall effect is to leave more
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memory available for applications. </p> <p>&lt;add links to memory mapping,
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NOR NAND&gt; </p> <p>If the ROM image is in a non-XIP ROM it has to be loaded
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into RAM before it can be executed. The ROM image is split into two parts: </p> <ul>
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<li id="GUID-74FB13BD-87C6-5591-B522-E2853BB89B76"><p>Paged </p> </li>
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<li id="GUID-E3226DFC-D8C3-5E31-A188-D9549697C210"><p>Unpaged </p> </li>
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</ul> <p>The unpaged part of the ROM image is loaded by the bootloader and
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it always present in RAM. The paged part of the ROM image is paged in on demand. </p> </section>
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<section id="GUID-B4DB09C1-B16C-4A45-ADCF-C0A10D577CFA"><title>Using ROM Paging</title> <p>The type of paging used and the
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area of memory to use first is specified in the oby and mmp files and then
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built by using specific parameters in the buildrom utility. </p> </section>
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</conbody><related-links>
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<link href="GUID-0AFF5666-6BF9-5022-ADBC-5EFFA743B288.dita"><linktext>ROM Paging
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Guide</linktext></link>
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<link href="GUID-5A71755A-E67F-5007-8C55-5B8FA65B3C04.dita"><linktext>ROM file
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system</linktext></link>
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<link href="GUID-D6C2202C-778C-558A-97AA-649CD6DB5E87.dita"><linktext>ROFS file
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system</linktext></link>
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</related-links></concept>