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Original question:

accessing C structure members in c28x assembly

Compiler/LAUNCHXL-F28069M: Accessing C variable from Assembly function

Juan Gomez
Intellectual 335 points

Part Number: LAUNCHXL-F28069M

Tool/software: TI C/C++ Compiler

Hello Community,

I am working with the F28069M EVM and I'm trying to implement a assembly function, inside a C project, which has to use variable declare, externally, in .C file
The variable inside the .c file is: RunPt

and this is de code I had in the .asm file:

	;.cdecls C,NOLIST	%{ #include "x00_RTOS.h" %}

	.def _OS_Start
    .global _OS_Start
    .ref RunPt
***********************************************************************
* Function: codestart section
*
* Description: Branch to code starting point
***********************************************************************
    .sect "OS_Start"
_OS_Start:
	EALLOW
	MOVZ 	AR2,@RunPt
	MOV		@SP,AR2
EDIS
	LRETR

The output error is that the compiler:

 undefined first referenced
  symbol       in file     
 --------- ----------------
 RunPt     ./x00_OSasm.obj 
 
error: unresolved symbols remain

Does anyone know how to resolve this problem?

  • 0
    TI__Mastermind 27200 points

    To reference a variable declared in a C file in an assembly module, you'll need to prefix the variable name with an underscore.  Change the variable name in the assembly file to _RunPt, leaving the C name unchanged.  This was done in the thread you referenced with the variable "MyVar".

    Regards,

    Richard

  • 0 in reply to Richard Poley
    Intellectual 335 points

    Hello Richard,

    Thank you for your answer. The underscore prefix needs to be added to the variable name at every reference/usage of it inside the .asm code.

    ;	Created on: Mar 21, 2020
;	 Author: JuanFco

     .def _OS_Start
    .global _OS_Start
    .ref _RunPt
***********************************************************************
* Function: codestart section
*
* Description: Branch to code starting point
***********************************************************************
	.text
    .sect "OS_Start"
_OS_Start:	.asmfunc
	EALLOW
	MOVZ 	AR2,@_RunPt
	MOV		@SP,AR2
	EDIS
	LRETR
	.endasmfunc

    I would like to add that, the correct implementation is mentioned in the following document form TI: SPRU513C.pdf, Page 57, Section 3.14 Debugging Assembly Source, Example 3-4. Viewing Assembly Variable as C Types

    Regards.