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RealView Linker and Utilities Guide
Preface Introduction The Linker Command Syntax Using the Basic Linker Functionality Accessing Image Symbols Using Scatter-loading Description Files About scatter-loading
Symbols defined for scatter-loading Specifying stack and heap using the scatter-loadin When to use scatter-loading Scatter-loading command-line option Images with a simple memory map Images with a complex memory map Formal syntax of the scatter-loading description f BNF notation and syntax Overview of the syntax of scatter-loading descript Load region description Execution region description Input section description Resolving multiple matches Resolving path names Expression evaluation in scatter-loading files Examples of specifying region and section addresse Selecting veneer input sections in scatter-loading Creating root execution regions Placing regions at fixed addresses Using overlays to place sections Assigning sections to a root region Reserving an empty region Placing ARM libraries Creating regions on page boundaries Using preprocessing directives Equivalent scatter-loading descriptions for simple Type 1, one load region and contiguous execution r Type 2, one load region and non contiguous executi Type 3, two load regions and non contiguous execut Using the ARM Librarian Using fromelfWhen to use scatter-loading
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| Home > Using Scatter-loading Description Files > About scatter-loading > When to use scatter-loading | |||
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 descriptions are either necessary or very useful are:
- Complex memory maps
Code and data that must be placed into many distinct areas of memory require detailed instructions on which section goes into which 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 I/O
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.
- 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, therefore, almost always required for implementing embedded systems because these use ROM, RAM, and memory-mapped I/O.
Note
If you are compiling for the Cortex-M3 processor, this has a fixed memory map and so you can use a scatter-loading description file to define both stack and heap.
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