I should have google bit more before doing this post.

In a meenwhile found partly an answer. It is described very good here:
http://www.esacademy.com/automatio...er/c05.htm

So my conclusion is that I can use subfunctions with USING if I really know what am I doing. And even a better way is to define the REGISTERBANK pargma for subfuctions, because than no push and pop is done with the PSW.

It would be nice to have this thing in the 8051 FAQ section even if it is compiler specific. I think lot of trouble can be saved with it.

For my other question there is a directive NOREGPARMS.
http://www.keil.com/support/m...gparms.htm

greetings
Attila