Thanks for reply Steve,

>..anywhere thats timing critical. An >edge happens in an instant.

Ok, do you mean with this that I can lost an event if the interrupt is edge triggered? Is this avoidable with level trig. interrupt? Let me re-read the datasheets again... I can´t imagine how can I lost an event with edege triggered int. unless the event width is less than 1uS wide (@12Mhz).
Could you explain me more about this?

>Also where an event is marked by a >change of state, not by the state you >have entered.

Change of state...Hmmm...let me think...If you are talking about detecting both falling and rising edges of an external signal, I am not able to figure out how to do it using only interrupts without polling the pin.

I am afraid that I don´t understand your thinkings about change of state, Please.....

Fran Dominguez