Place Functions in RAM with SEGGER Linker

This article will show how to place a function into RAM with SEGGER Linker and Embedded Studio. To make sure this stays valid after a reset/reboot of the device the function must be initialized during startup by copying them from Flash to RAM. That way the application also works stand alone without a debugger.

How to

• Create a function you want to place in RAM
• Open the SEGGER Linker script file and place the specific function symbol in a section. This can be done e.g. as follows in your application source code:

void __attribute((section(".ramfunc"))) MyFunc(void) {
  ...
}

• Alternatively you can place symbols directly in the SEGGER Linker script file as shown in the example project linked below
• Now place the section in the linker script in RAM

place in RAM       { section .ramfunc };

• Now make sure it is initialized by copy even without a debugger

initialize by copy { section .ramfunc };

For more information see the SEGGER Linker reference manual UM20005

Example project

The following example project will show an example implementation of such RAM function. A simple function Count() is created which is placed in RAM and executed.

Prerequisites

To be able to build and debug the project the following prerequisites must be met:

• SEGGER Embedded Studio V7.32 or later
• Any J-Link
• Cortex-M Trace Reference Board

Project files

RAMFunc_Example.zip