Place small ASM code at specific flash location

Calin,

You must use the .sect directive, as well as correspond that with a section in your linker CMD file.

I just happened to be working on a similar thing. Check the attached project, where several pieces of code and data are allocated throughout the memory, and one in particular (.const) is allocated to a fixed address.

Hope this helps,

Rafael

Hello Rafel,

    I placed some constant data into a specific flash address with this approach:

#pragma RETAIN(watermark)
#pragma location=0x1604
const unsigned char watermark[] = {'M','e','t','r','o','l','o','g'};

    It worked fine.

    Now I tried your idea:

    - Created a SECTION { .blentry    : {} > 0x1600 ... at lnk_msp430f149.cmd
    - Created a new .s file, with these lines:

.sect .blentry
br     #0123h

    It compiles ok, however no data is placed at the correct address (0x1600). Am I missing something here?

    Also, do you have idea how to refer to the linker function _c_int00? I tried br #_c_int00 (and some variations) but the linker keeps complaning about undefined "c_int00"

Thank you for your tips!

Calin

Calin,

A few details:

I am assuming you are putting a space before the "br #0123h" so it is properly considered as a mnemonic, right? 

If you don't have any label that references the assembly piece of code you just wrote, chances are the linker will automatically remove it (it is not called from anywhere). In this case, you could try to define a symbol and call it from your C source code.

   .sect .blentry
   .global my_func
   .asmfunc
my_func
   br     #0123h
   .endasmfunc

Not all details are accurate, therefore you should take a look at section 6.5 of the MSP Compiler User's Guide (a link to it is here)

I am unsure how the symbol _c_int00 would be called, but the section I referenced above mentions the & operand to access variables, therefore you could try the same with functions.

Hope this helps,

Rafael

Calin,

Ah, I forgot the .retain, which is mandatory for ELF...

Glad everything is working.

Cheers,

Rafael