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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-1A72F75A-1930-5C32-93B7-20F4934BCFAA" xml:lang="en"><title>ROM |
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13 Paging Overview</title><shortdesc>Memory may be conserved by only loading the parts of an execute |
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14 in place (XIP) image that are required at any given time. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 <section id="GUID-3CEEAF8D-F97A-55A8-AD34-5578A149EEFB"><title>Description</title> <p>If |
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16 an XIP ROM image is stored on an XIP media such as NOR flash, it does not |
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17 have to be copied into main memory before it can be executed. If it is stored |
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18 on non-XIP media, such as NAND flash, then it must be copied into main memory |
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19 before it can be executed. The entire XIP image can run to many megabytes, |
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20 and therefore use a lot of main memory. If ROM Paging is used, then only those |
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21 sections of the XIP image which are required are loaded into memory. Additional |
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22 sections are loaded as and when they are needed, and sections which have not |
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23 been used in some time can be discarded. The overall effect is to leave more |
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24 memory available for applications. </p> <p><add links to memory mapping, |
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25 NOR NAND> </p> <p>If the ROM image is in a non-XIP ROM it has to be loaded |
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26 into RAM before it can be executed. The ROM image is split into two parts: </p> <ul> |
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27 <li id="GUID-74FB13BD-87C6-5591-B522-E2853BB89B76"><p>Paged </p> </li> |
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28 <li id="GUID-E3226DFC-D8C3-5E31-A188-D9549697C210"><p>Unpaged </p> </li> |
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29 </ul> <p>The unpaged part of the ROM image is loaded by the bootloader and |
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30 it always present in RAM. The paged part of the ROM image is paged in on demand. </p> </section> |
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31 <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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32 area of memory to use first is specified in the oby and mmp files and then |
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33 built by using specific parameters in the buildrom utility. </p> </section> |
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34 </conbody><related-links> |
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35 <link href="GUID-0AFF5666-6BF9-5022-ADBC-5EFFA743B288.dita"><linktext>ROM Paging |
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36 Guide</linktext></link> |
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37 <link href="GUID-5A71755A-E67F-5007-8C55-5B8FA65B3C04.dita"><linktext>ROM file |
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38 system</linktext></link> |
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39 <link href="GUID-D6C2202C-778C-558A-97AA-649CD6DB5E87.dita"><linktext>ROFS file |
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40 system</linktext></link> |
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41 </related-links></concept> |