Mikroelektronika MIKROE-742 데이터 시트

mikroPascal PRO for AVR treats comments beginning with a 

“$”

immediately fol-

lowing an opening brace as a compiler directive; for example, 

{$ELSE}

. The compil-

er directives are not case sensitive.

You can use a conditional compilation to select particular sections of code to com-
pile, while excluding other sections. All compiler directives must be completed in the
source file in which they have begun.

Use directive 

$DEFINE

to define a conditional compiler constant (

“flag”

). You can

use any identifier for a flag, with no limitations. No conflicts with program identifiers
are possible because the flags have a separate name space. Only one flag can be
set per directive.

For example:

{$DEFINE Extended_format}

Use 

$UNDEFINE

to undefine (“clear”) previously defined flag.

Note: Pascal does not support macros; directives 

$DEFINE

and 

$UNDEFINE

do not cre-

ate/destroy macros. They only provide flags for directive 

$IFDEF

to check against.

Conditional compilation is carried out by the 

$IFDEF

directive. 

$IFDEF

tests whether

a flag is currently defined or not, i.e. whether a previous 

$DEFINE

directive has been

processed for that flag and is still in force.

Directive 

$IFDEF

is terminated with the 

$ENDIF

directive, and can have an optional

$ELSE

clause:

{$IFDEF flag}

<block of code>

{$ELSE}

<alternate block of code>

{$ENDIF}

First, 

$IFDEF

checks if flag is defined by means of 

$DEFINE

. If so, only 

<block of

code>

will be compiled. Otherwise, 

<alternate block of code>

will be compiled.

$ENDIF

ends the conditional sequence. The result of the preceding scenario is that only

one section of code (possibly empty) is passed on for further processing.

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- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 5