Defining Macro

Use the define preprocessor directive to define an HLI assembler macro.

The following listing defines a macro that clears the R0 register.

Listing: Defining the ClearR0 Macro

/* The following macro clears R0. */
#define ClearR0 {__asm CLR R0;}

The source code invokes the ClearR0 macro in the following manner:

ClearR0;

Then the preprocessor expands the ClearR0 macro:

{ __asm CLR R0 ; } ;

An HLI assembler macro can contain one or several HLI assembler instructions. As the ANSI-C preprocessor expands a macro on a single line, you cannot define an HLI assembler block in a macro. You can, however, define a list of HLI assembler instructions (refer the following listing).

Listing: Defining Two Macros on the Same Line of Source Code

/* The following macro clears R0 and R1. */
#define ClearR0and1 {__asm CLR R0; __asm CLR R1; }

The source code invokes this macro in the following way:

ClearR0and1;

The preprocessor expands the macro:

{ __asm CLR R0 ; __asm CLR R1 ; } ;

You can define an HLI assembler macro on several lines using the line separator \.

Note: This may enhance the readability of your source file. However, the ANSI-C preprocessor still expands the macro on a single line.

Listing: Defining a Macro on More than One Line of Source Code

/* The following macro clears R0 and R1. */
#define ClearR0andR1 {__asm CLR R0; \

                      __asm CLR R1;}

The source code invokes the macro in the following way:

ClearR0andR1;

The preprocessor expands the ClearR0andR1 macro:

{__asm CLR R0; __asm CLR R1; };