Hello, and thanks for your replies!
I'm sure they will solve my problem.

I originally took the code from an example which is still available in several places in internet, and without further studying it I applied it into my application, because it seemed to work fine 3 years until now. I remember I sometimes wonderd that "setb ti" in the initialization but let it be there.

I use mixed C and assembly language because I do assembler optimization for some parts of the code. I just was too lazy to translate everything into one language for my question. Probably all the members of this forum are accustomed to both languages anyway. Sorry about the bad looking code!

To Jan: You are right, next time I will study FAQs more before asking stupid questions here. Sorry! I have nothing to do with Turku and any links or schools in there or anywhere else.

Thanks again to all of you!
Best regards,
Ari