Hi everybody, i have one question for you.

I have to read a byte with the usart and save this value in a variable for control the main program. I am receiving this byte correctly with the usart but in the main if i do this, the program never works:

int main(){
unsigned char status=0x00;
. . .

while(1){
status=read_status();
switch(status){
case A: ...
case B: ...
....
}
}
}

if I add a printf at the end of the while the program works OK, can someone explain me why the printf makes the program works ?
Thanks everybody. Regards.

You don't specify a compiler, but I'd guess you either have a buggy compiler, issues with optimization, or you're not defining peripheral registers as volatile properly.

Without knowing more about the tool chain, compiler settings, linker scripts, etc. it could be any number of things.

Look at the assembler code that's being generated for your application, it might be more enlightening about what's really going wrong.