[sdiy] Binary state change detector

[Peter Grenader]

I am looking for a circuit that detects when the state (number) of a  four
bit binary word changes state.

I've been putzing around with the idea of using a 74C85 in conjunction with
a 4242 (using the 42 to latch the the last occurrence of change and feed it
back into the C85 for the next comparison, and then running that output
through a oneshot to keep it from disappearing as soon as it is sensed, but
to this I have a question:

How short of a incoming pulse does a oneshot require in order to react?  For
instance, another perfect example is a sequencer reset pulse coming from one
of it's stage gate outputs.  As soon as it goes high, the reset function
occurs and the gate is no longer high.  Will that pulse width, as short as
it is, be long enough for a oneshot to react?  Although this isn't my
application, its the same idea and if it's long enough, me thinks I've got
the circuit I need here.

If not, I'm totally screwed and am asking the masters here if they have any
other suggestions.

thanks in advance,

Peter