Re: gEDA-user: Tools for timing diagrams for digital signals

[Andrew Bardsley <bardslea@cs.man.ac.uk>]

On Wed, 12 Feb 2003 steve@spiketech.com wrote:

> Andrew,
> 
> I've got to disagree with you here.
> 
> Timing waveforms are a succinct way to illustrate relationships
> between signals. They do a GREAT job in specifications of
> interfaces in particular. I would wager they do the best job
> in trying to define interfaces in particular.
> 
> If you use them in your design efforts initially without worrying
> about how the nano-seconds, but just which clock something occurs
> you can also use them to GREAT effect in figuring out how
> a state machine NEEDS to work in the first place.

Interesting points.  I still disagree though, the fact that a timing
diagram implies by the placement of events relationships between
signals which may not exist.  Timing diagrams are often ambiguous about
sets of transitions for which there is no required ordering but one
is often present in common usage.  I probably have a skewed view here
as I don't generally work with clocked circuits.

> Timing diagrams still serve a place in my design bag of tricks.

Agreed, I usual used them to expand particular examples of interfaces
but I prefer to specify interfaces in other ways.

Actually, from a GTKWave point of view, being able to annotate with
causal-relationship arrows (either by hand or from a textual/graphical
spec) would be quite cool and very handy for visualising relationships
between signals in real communications (or example communications acting
as specs.).
Hmm, I should prob. think about this.  My main interest in GTKWave has
always been in adapting it to show request-acknowledge channel
communications for my own tools.  I've begun to thing recently of
extending this to show abstracted-from-signals channel comms. in the
generated circuits from my tools.  Perhaps arrow annotation would be
good for that.

What do you think?

- Andrew 
    __________________
___/Dr Andrew Bardsley\_________________________________________
University of Manchester Dept. of Computer Science  Amulet Group
Research Associate bardsleyATcs.man.ac.uk  Tel: +44 161 275 6844
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