Mikroelektronika MIKROE-350 Fiche De Données

#IFDEF flag THEN

block of code

[ #ELSEIF flag_1 THEN

block of code 1

...
#ELSEIF flag_n THEN

block of code n ]

[ #ELSE

alternate block of code ]

#ENDIF

First, 

#IFDEF

checks if flag is set by means of 

#DEFINE

. If so, only block of code will

be compiled. Otherwise, the compiler will check flags 

flag_1 .. flag_n

and exe-

cute the appropriate block of code i. Eventually, if none of the flags is set, alternate
block of code in 

#ELSE

(if any) 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. The
processed section can contain further conditional clauses, nested to any depth;
each 

#IFDEF

must be matched with a closing 

#ENDIF

.

Here is an example:

' Uncomment the appropriate flag for your application:
'#DEFINE resolution8
'#DEFINE resolution10
'#DEFINE resolution12

#IFDEF resolution8 THEN

... ' code specific to 8-bit resolution

#ELSEIF resolution10 THEN

... ' code specific to 10-bit resolution

#ELSEIF resolution12 THEN

... ' code specific to 12-bit resolution

#ELSE

... ' default code

#ENDIF

The compiler sets directives upon completion of project settings, so the user does-
n't need to define certain flags.
Here is an example:

#IFDEF ATMEGA16 ' If ATmega16 MCU is selected

#IFDEF ATMEGA128 ' If ATmega128 MCU is selected

In some future releases of the compiler, the JTAG flag will be added also.

See also predefined project level defines.

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- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 5