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Call functions

nels eira

Hi,

I have some assembly routines located in ROM memory, for example asmfunc that is located at address 0xF700 - is absolute address of flash memory.

The program memory is organized:
ROM code from address 0xF000 - 0xFFFF
Flash code from address 0x0000 - 0xEFFF

I have my C code and I want to call from C the assembly function asmfunc located at address 0xF700, how I can do this?

I know to call function asmfunc if my code is in Assembly using for example this:

asmfunc equ 0xF700
. .
lcall asmfunc
. .

Thanks,
Nels

Parents
  • 0

    The C convention is that function names start with an underscore. So, name your asm functions accordingly, and export the names of the functions with "public".

    Asm.a51

    PUBLIC _AsmFunc
_AsmFunc:
        RET

    Asm.h

    extern void AsmFunc (void);

    C.c

    void main (void)
    {
    AsmFunc();
    }

    If you're trying to jump to a particular address that you maintain manually, rather than letting the linker do it for you as above, then you can do something like: #define AsmFuncAddr 0xF700 *(AsmFuncAddr)(); to cast the integer constant to a function pointer and call the function. Generally if you go this route, it's a good idea to have vector table so that there's only one hardcoded address.

Reply
  • 0

    The C convention is that function names start with an underscore. So, name your asm functions accordingly, and export the names of the functions with "public".

    Asm.a51

    PUBLIC _AsmFunc
_AsmFunc:
        RET

    Asm.h

    extern void AsmFunc (void);

    C.c

    void main (void)
    {
    AsmFunc();
    }

    If you're trying to jump to a particular address that you maintain manually, rather than letting the linker do it for you as above, then you can do something like: #define AsmFuncAddr 0xF700 *(AsmFuncAddr)(); to cast the integer constant to a function pointer and call the function. Generally if you go this route, it's a good idea to have vector table so that there's only one hardcoded address.

Children
  • 0 in reply to Drew Davis

    "The C convention is that function names start with an underscore."

    C51 also has other conventions - you must read the Manual...

  • 0 in reply to Andy Neil

    Hi,

    First of all I read the manual. I think the problem is not "underscore" in assembly function but:

    My flash memory is mapped 0x0000-0xF000 for flash code, 0xF000-0xFFFF this address is re-mapped to other memory - ROM memory, here I have assembly code with some routines.

    so in my case I have two firmware projects! one project_rom.Uv2 written in assembly located in ROM, other project_flash.Uv2 located in the flash.

    I would like to call directly some assembly routines located in ROM from "C" in the flash memory --> that corresponds to the project_flash.Uv2

    Thanks you.