Wake on EXT isr question

[iso9001]

Can a pic detect a change (and then wake from sleep) on a port if it goes from no conection to ground ? (Float to Low) ?

[Mark]

No connection can pick up stray noise and cause you to int when you don't want it. But to answer your question, it has to see the change so if the input were to go to ground then it would need to be high first. The only way to ensure this is to put it there.

[iso9001]

Thats what i figured. Thanks,


Well.. I guess I could put a pullup on the line and then the int could be any change or L_to_H... problem is it will always be draining a little power then.

Maybe I could put some crazy high value resistor in there though. Is there a min value amperage value the pic can read ?

Ie: if I have 5V to a 100k resistor, obviously the strength of the signal will be low, but is there a "too low" amperage ?

[Mark]

The input impedance of the input is pretty high. What you are concerned with is noise affecting the signal. If the impedance is too high, then the noise could still affect the signal.