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<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>