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[Cortex-M3] Execution code from RAM during Flash Programming

Rohit Pathak
I am writing a bootloader for Cortex M3 Toshiba controller.

During Flash Programming I need to execute code from RAM as entire Flash is inaccessible during write/erase operations

I wish to know how to copy code from FLASH to RAM and execute that code from RAM.

Thanks...
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  • Note: This was originally posted on 15th March 2012 at http://forums.arm.com

    Hi Joseph,

    Thank you very much for your reply.

    Yes I think this will be a helpful way. I will try to implement this way.
    I will get back to you if I have any other doubts regarding the same.
    Thank you very much for your support..

    Regards,
    Rohit



    Hi Rohit,

    In this case you could develop the bootloader and flash programming code as two separate projects.
    The flash programming project is compiled and link using SRAM as program address.
    Then you can generate hex image, and insert this into your boot loader project as a constant array.
    Inside your boot loader, you can copy this constant array into SRAM.

    To jump from boot loader to flash programming code, personally I got used to use embedded assembly:

    /* ARM RVDS or Keil MDK */
    __asm void jump_to_sram(void)
    {
       LDR   R0,=0x20000000  ; starting address of program in SRAM.
       LDR   R1,[R0]  ; Get initial MSP value
       MOV   SP, R1  ; Set SP value
       LDR   R1,[R0, #4] ; Get initial PC value
       BX R1
    }

    You can use function pointer to do the same.
    regards,
    Joseph
Reply
  • Note: This was originally posted on 15th March 2012 at http://forums.arm.com

    Hi Joseph,

    Thank you very much for your reply.

    Yes I think this will be a helpful way. I will try to implement this way.
    I will get back to you if I have any other doubts regarding the same.
    Thank you very much for your support..

    Regards,
    Rohit



    Hi Rohit,

    In this case you could develop the bootloader and flash programming code as two separate projects.
    The flash programming project is compiled and link using SRAM as program address.
    Then you can generate hex image, and insert this into your boot loader project as a constant array.
    Inside your boot loader, you can copy this constant array into SRAM.

    To jump from boot loader to flash programming code, personally I got used to use embedded assembly:

    /* ARM RVDS or Keil MDK */
    __asm void jump_to_sram(void)
    {
       LDR   R0,=0x20000000  ; starting address of program in SRAM.
       LDR   R1,[R0]  ; Get initial MSP value
       MOV   SP, R1  ; Set SP value
       LDR   R1,[R0, #4] ; Get initial PC value
       BX R1
    }

    You can use function pointer to do the same.
    regards,
    Joseph
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