INT_RB problem - pic18f2550

[Pichuqy_1]

PCM programmer,

Could you explain to me, please, why the code #elif HIGHTOLOW, is never executed?

[temtronic]

I'll try to explain...

That #if...else... is a 'pre processor' directive

..from the manual
The pre-processor evaluates the constant expression and if it is non-zero will process the lines up to the optional #ELSE or the #ENDIF.

So what happens is the compiler, on the 1st pass, determines which of the if 'sections' it will then 'process' or compile during the 2nd pass which then gets put INTO your program.

This is not the same 'If then else' that you put INTO your program that does 'this' or 'that' based upon variables when your program runs.

hope this helps
Jay

[PCM programmer]

[Ttelmah]

Key is to get into your head, the difference between 'source code', and the
'runtime' code this generates.

#if is a command executed at _compile_ time, affecting which part of the
source code is actually compiled.

if is a command executed at _run time_ affecting which part of the code
actually executes.

[temtronic]

You're wrong..but I understand why you're confused.

You need to read Mt. T's reply again

#IF (condition is true...) CREATES code that gets loaded into the program that you download into the PIC

if (condition is true) EXECUTES code WHILE the program is running

If you look at some of the CCS suppled example programs you'll see at the top of the code something like

#IF __PCM__
...do this code
#ELIF __PCH__
...do this code
#ENDIF

What this is doing is telling the compiler to 'configure' or 'create' a section of code based upon what type of PIC you're using. It then adds that code
to the overall program THEN compiles it.
Only ONE section of code is put into the program.

I understand English is difficult ! I live in Canada and after 65 years STILL cannot understand some of it !!

Hope this helps
Jay