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Technical Support
On-Line Manuals
Linker User Guide
Conventions and feedback
Overview of the linker
Linking models supported by armlink
Image structure and generation
Using linker optimizations
Getting information about images
Accessing and managing symbols with armlink
Using scatter files
About scatter-loading
When to use scatter-loading
Scatter-loading command-line option
Images with a simple memory map
Images with a complex memory map
Linker-defined symbols that are not defined when s
Specifying stack and heap using the scatter file
What is a root region?
Creating root execution regions
Using the FIXED attribute to create root regions
Placing functions and data at specific addresses
Placing a named section explicitly using scatter-l
Placing unassigned sections with the .ANY module s
Examples of using placement algorithms for .ANY se
Example of next_fit algorithm showing behavior of
Examples of using sorting algorithms for .ANY sect
Selecting veneer input sections in scatter-loading
Using __attribute__((section("name"))) t
Using __at sections to place sections at a specifi
Restrictions on placing __at sections
Automatic placement of __at sections
Manual placement of __at sections
Placing a key in flash memory using __at
Placing a structure over a peripheral register usi
Placement of sections with overlays
About placing ARM C and C++ library code
Example of placing code in a root region
Example of placing ARM C library code
Example of placing ARM C++ library code
Example of placing ARM library helper functions
Reserving an empty region
About creating regions on page boundaries
Overalignment of execution regions and input secti
Using preprocessing commands in a scatter file
Expression evaluation in scatter files
Using expression evaluation in a scatter file to a
Equivalent scatter-loading descriptions for simple
Type 1 image, one load region and contiguous execu
Type 2 image, one load region and non-contiguous e
Type 3 image, two load regions and non-contiguous
Scatter file to ELF mapping
Linker User Guide
When to use scatter-loading
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The command-line options to the linker give some control over the placement of data and code, but complete control of placement requires more detailed instructions than can be entered on the command line.
Situations where scatter-loading is either required or very useful:
- Complex memory maps
Code and data that must be placed into many distinct areas of memory require detailed instructions on where to place the sections in the memory space.
- Different types of memory
Many systems contain a variety of physical memory devices such as flash, ROM, SDRAM, and fast SRAM. A scatter-loading description can match the code and data with the most appropriate type of memory. For example, interrupt code might be placed into fast SRAM to improve interrupt response time but infrequently-used configuration information might be placed into slower flash memory.
- Memory-mapped peripherals
The scatter-loading description can place a data section at a precise address in the memory map so that memory mapped peripherals can be accessed.
- Functions at a constant location
A function can be placed at the same location in memory even though the surrounding application has been modified and recompiled. This is useful for jump table implementation.
- Using symbols to identify the heap and stack
Symbols can be defined for the heap and stack location when the application is linked.
Scatter-loading is usually required for implementing embedded systems because these use ROM, RAM, and memory-mapped peripherals.
See also- Concepts
| Copyright © 2007-2008, 2011-2012 ARM. All rights reserved. | ARM DUI 0377D |
| Non-Confidential | ID062912 |
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| Home > Using scatter files > When to use scatter-loading |
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