diff -r 578be2adaf3e -r 307f4279f433 Adaptation/GUID-1A72F75A-1930-5C32-93B7-20F4934BCFAA.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Adaptation/GUID-1A72F75A-1930-5C32-93B7-20F4934BCFAA.dita Fri Oct 15 14:32:18 2010 +0100 @@ -0,0 +1,41 @@ + + + + + +ROM +Paging OverviewMemory may be conserved by only loading the parts of an execute +in place (XIP) image that are required at any given time. +
Description

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.

<add links to memory mapping, +NOR NAND>

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:

    +
  • Paged

  • +
  • Unpaged

  • +

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.

+
Using ROM Paging

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.

+
+ROM Paging +Guide +ROM file +system +ROFS file +system +
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