CCS/CC3220MODA: Interfacing assembly with c/c++

joe boer

Part Number: CC3220MODA

Tool/software: Code Composer Studio

This should be simple but I cannot seem to find the answer; I am optimizing a bit of c/c++ code with assembly and need to interface with a few global variables declared on the c/c++ side. I cant seem to find how to do this. So for example:

==== c/c++ side defines these variables

int globalVar;

int globalArray[10];

=====

.global myfunc

myfunc;

ldr r0, <value of globalVar>

ldr r1, <address of globaVar>

ldr r2, <address of globalArray>

With the stuff between brackets <> what I don't know. I have the "ARMAssemblyLanguageToolsv18.1.0.LTS" from 2018 doc but this is either not documenting it or I missed it.

over 6 years ago

0 George Mock over 6 years ago

TI__Guru**** 253380 points

Please search the ARM compiler manual for the sub-chapter titled Interfacing C and C++ With Assembly Language.

Thanks and regards,

-George

0 joe boer over 6 years ago in reply to George Mock

Expert 1280 points

Thanks George, that was helpful.

The example shows the interaction between .global and .field directives

.global asmfunc

.global gvar

asmfunc:

gvar_a .field gvar, 32

The .field directive is not really explained in this document, is the '32' indicating the size of gvar_a in bits? So on a 64bit machine one could use 32 or 64 depending on addressing mode etc? I've got my code working without the '32' value, is this the default then?

0 George Mock over 6 years ago in reply to joe boer

TI__Guru**** 253380 points

All of the assembler directives, such as .field, are documented in the ARM assembly tools manual. Please search for the chapter titled Assembler Directives.

Thanks and regards,

-George

0 joe boer over 6 years ago in reply to George Mock

Expert 1280 points

thanks, good stuff. wish it was more discoverable/easier to find though.

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CCS/CC3220MODA: Interfacing assembly with c/c++