AN3350 datasheet(71/185 Pages) STMICROELECTRONICS

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AN3350

Working with the assembler

Doc ID 018512 Rev 2

71/185

#else

// this code is processed if both conditions are false

#endif

Note:

The #else and #elif clauses are optional. You can use several #elif clauses in

succession. You can also nest #if conditions.

Another illustration of conditional assembly is Example 11.

Example 11 Conditional assembly

#if %defined(INTERRUPTS_LEVEL)

nop

#if INTERRUPTS_LEVEL < 3

or.f a,d,a

#endif

#else

ori.f a,d,TRNR

#endif

#if

The #if directive, defined as #if expr, results in the processing of code only if the

numeric expression expr is evaluated to an integer other than zero. All expression elements

must be known at the preprocessing point when expressions are met, or error messages

occur.

The condition of the #if clause is preprocessed before evaluation. Therefore it is possible

to use preprocessor macros and operators as parts of the expression.

#ifdef

The #ifdef directive, defined as #ifdef macro, results in the processing of code only if

the macro has been defined by the #define directive.

#ifndef

The #ifndef directive, defined as #ifndef macro, results in the processing of code only

if the macro has not been defined by the #define directive.

#elif

The #elif directive, similar to #if, must follow an #if or #elif directive. This offers

another expression to test in case the previous conditions failed.

#else

The #else directive results in the processing of following code lines, in the instance that all

conditions defined by the else's corresponding #if and #elif have failed.

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