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Linker User Guide

Preface Overview of the Linker Linking Models Supported by armlink Image Structure and Generation Linker Optimization Features Getting Image Details Accessing and Managing Symbols with armlink Scatter-loading Features The scatter-loading mechanism Overview of scatter-loading When to use scatter-loading Linker-defined symbols that are not defined when s Specifying stack and heap using the scatter file Scatter-loading command-line options Scatter-loading images with a simple memory map Scatter-loading images with a complex memory map Scatter file with link to bit-band objects Root execution regions Root execution region and the initial entry point Root execution regions and the ABSOLUTE attribute Root execution regions and the FIXED attribute Methods of placing functions and data at specific Placement of code and data with __attribute__((sec Placement of __at sections at a specific address Restrictions on placing __at sections Automatic placement of __at sections Manual placement of __at sections Placement of a key in flash memory with an __at se Mapping a structure over a peripheral register wit Example of how to explicitly place a named section Placement of unassigned sections with the .ANY mod Placement rules when using multiple .ANY selectors Command-line options for controlling the placement Prioritization of .ANY sections Specify the maximum region size permitted for plac Examples of using placement algorithms for .ANY se Example of next_fit algorithm showing behavior of Examples of using sorting algorithms for .ANY sect Behavior when .ANY sections overflow because of li Placement of veneer input sections in a scatter fi Placement of sections with overlays Reserving an empty region Placement of ARM C and C++ library code Specifying ARM standard C and C++ libraries in a s 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 Creation of regions on page boundaries Overalignment of execution regions and input secti Preprocessing of a scatter file Example of using expression evaluation in a scatte Equivalent scatter-loading descriptions for simple Command-line options for creating simple images Type 1 image, one load region and contiguous execu Type 2 image, one load region and non-contiguous e Type 3 image, multiple load regions and non-contig How the linker resolves multiple matches when proc How the linker resolves path names when processing Scatter file to ELF mapping Scatter File Syntax Linker Command-line Options Linker Steering File Command Reference Via File Syntax

Scatter file with link to bit-band objects

7.1.8 Scatter file with link to bit-band objects

In devices that are based on the ARM® Cortex®‑M3 processor or ARM Cortex‑M4 processor, the SRAM and Peripheral regions each have a bit-band feature.

You can access each bit in the bit-band region individually at a different address, called the bit-band alias. For example, to access bit[13] of the word at 0x20000001, you can use the address 0x22000054.
The following table shows the bit-band regions and aliases within the SRAM and Peripheral memory regions.

Table 7-1 ARMv7-M bit-band regions and aliases

Memory region
Description
Address range
SRAM
Bit-band region
0x20000000-0x200FFFFF
 
Bit-band alias
0x22000000-0x23FFFFFF
Peripheral
Bit-band region
0x40000000-0x400FFFFF
 
Bit-band alias
0x42000000-0x43FFFFFF
The following is an example scatter file that links bit-band objects.
FLASH_LOAD 0x20000000
{
  RW 0x20000000  ; RW data at the start of bit band region
  {
    * (+RW-DATA)
  }
  RO +0 FIXED        ; Followed by the RO Data
  {
     * (+RO-DATA)
  }
  CODEDATA +0   ; Followed by everything else
  { 
    * (+RO-CODE)
    * (+ZI)             ; ZI follows straight after
  }
  ARM_LIB_HEAP  +0 EMPTY 0x10000  ; heap starts after that
  {
  }
  ARM_LIB_STACK 0x20100000 EMPTY -0x10000    ; stack starts at the 
                                             ; top of bit band region
  {
  }
}
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