Great!
really my problem was only to set something at the beginning of the code (particularly the cristal speed and so the reload value for timers), so I thought to do this by setting a jumper
But the answers of you all have extended my vision and now I have much more ideas on this and other problems :-)
thanks everybody!
(I also read the links, which are favourites of Erik :o) )
Best regards,
and thanks very much
teo.