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CCS/MSP430F5438A: MSP430 GCC: Placing Variables to dedicated RAM / FLASH addresses

Marco Steinborn
Prodigy 200 points
Part Number: MSP430F5438A

Tool/software: Code Composer Studio

I have selected the compiler version GNU v8.3.1.25 (Mitto Systems Limited) with the linker command file of msp430f5438a. 

Now I want to set variables in the memory of (linker file example):

RAM: ORIGIN = 0x1C00, LENGTH = 0x4000 /* END=0x5BFF, size 16384 */

ROM (rx) : ORIGIN = 0x5C00, LENGTH = 0xA380 /* END=0xFF7F, size 41856 */

HIROM (rx) : ORIGIN = 0x00010000, LENGTH = 0x00035BFF

How can is set variables to a specific address in the memory e.g. 0x001c00 (RAM) or 0x005c00 (FLASH)? With #pragma LOCATiON(...) , I already tried , but it seems that does not work with GCC. And I do not want to create extra sections in the linker file; is that possible?

  • 0
    TI__Guru**** 245180 points

    Marco Steinborn said:
    I do not want to create extra sections in the linker file; is that possible?

    I'm not aware of any way to do that.  The only way I know is to use the section variable attribute to put the variable in a section which you name.  In the linker script, allocate that section to the desired address.

    Thanks and regards,

    -George

  • 0
    Expert 2410 points

    This is not currently possible to do entirely from C/C++. This year we are actually adding the functionality to be able to use a "location" attribute on functions and data to place them at a specific address.

    As George mentioned, you need to use the "section" attribute with associated linker script updates.

    A brief example:

    int __attribute__((section(".qdata.2000"))) var_at_0x2000 = 1;
int __attribute__((section(".qdata.2100"))) var_at_0x2100 = 2;

    Then in the linker script (0x1C00 is the start address of RAM):

      .data :                                                                         
  {                                                                               
    .....................
                                
    . = 0x2000 - 0x1c00;                                                          
    *(.qdata.2000)                                                                
    . = 0x2100 - 0x1c00;                                                          
    *(.qdata.2100)                                                                
                                                                                  
    ....................                                                
  } > RAM AT> ROM

    Now in the linked output executable:

    $ nm a.out | grep var_at
00002000 D var_at_0x2000
00002100 D var_at_0x2100

    There's plenty of useful documentation on linker script placement here: https://sourceware.org/binutils/docs/ld/Location-Counter.html#Location-Counter