Accessing assembly variables in an ANSI-C source file

A variable or constant defined in an assembly source file is accessible in an ANSI-C source file.

The variable or constant is defined in the assembly source file using the standard assembly syntax.

Variables and constants must be exported using the XDEF directive to make them visible from other modules, as listed in the following listing:

Listing: Example of data and constant definition


          XDEF  ASMData, ASMConst
DataSec:  SECTION

ASMData:  DS.W  1      ; Definition of a variable

ConstSec: SECTION

ASMConst: DC.W  $44A6  ; Definition of a constant

We recommend that you generate a header file for each assembler source file. This header file should contain the interface to the assembly module.

An external declaration for the variable or constant must be inserted in the header file, , as listed in the following listing:

Listing: Example of data and constant declarations


/* External declaration of a variable */
extern int       ASMData;

/* External declaration of a constant */

extern const int ASMConst;

The variables or constants can then be accessed in the usual way, using their names, , as listed in the following listing:

Listing: Example of data and constant reference



  ASMData = ASMConst + 3;