[En-Nut-Discussion] Best way to implement a time-critical RS485driver

[Christian.Schilmoeller at camco.de]

By  trouble I just meant the following:
If C-functions are called from within interrupt handlers, the compiler has 
to save/push (and restore/pop afterwards) the registers that might be 
altered by the C-function, regardless if there are in fact altered or not. 
I observed this behaviour by looking into the compiler-generated 
*.lst-files - although it might be affected by the different optimization 
switches.
Therefore it could make sense to avoid function calls in irq handlers at 
all - or replace them by macros.