[sdiy] Binary state change detector

[Czech Martin]

if it is all clocked, why don't you use a clocked FF
to hold the information. This is ok as long as you can make
up for the additional delay of one clock, which is possible 
for many applications.

Why build some asynchronous logic when synchronous stuff
will do the job?

m.c.

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Peter Grenader
> Sent: Mittwoch, 8. Oktober 2003 16:21
> To: Synth DIY
> Subject: [sdiy] Binary state change detector
> 
> 
> 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
> 
>