It helpd to define what a keypress is. If a keypress is a signal condition
that exists for more than 10 msec then theory says that if you have a
latency of one half of that or less in the method of aquiring it, it will
be aquired successfully.

So if you 'loop' fast enough to read the keys every 5 msec or have
response latency for interrupts of less than 5 msec then you should not
miss any key events. The 10 msec comes from the typical minimum acceptable
keypress time which is 100 msec, divided by 10 to make 'very sure'. You
will need some debouncing anyway.

With some keys it is possible to 'key' even shorter pulses by hand. In
that case the 'minimum keypress time' can be taken as 3x the contact
bounce time given by the manufacturer, and the latency will have to be 1/2
or even 1/3 of the bounce time.

hope this helps,

Peter

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics