Thanks all. But I've already wrote some asm routines for I²C from the 80C535, so I know what I²C is. The problem is that, when I use the Philips aproach I have some problems.
I use (probeley not know to anyone of you) the ELEKTUUR monitor program and development print for the 80552. Well here the program address starts at 2100 so I've start writing my code (I²C) at this address, put the higher address in the HADDR variable and what do I get Nopes, zero. Just the SCL line gose down and thats it. I think there may be A bug in the monitor or the philips I²C source routines.

J. Leroy