Re: [TCLUG:5462] "Race Condition"?

[Mike Lindahl <mlindahl@phoenix.Princeton.EDU>]

Are you talking about a race condition in terms of digital logic?  If so,
race occurs whenever there is uninhibited feedback that causes a circuit
to oscillate back and forth between high and low.

For instance, if you have an R-S latch made out of NOR gates, you cannot
have the sequence from R=1, S=1 to R=0, S=0 (Both of these inputs are
forbidden) because when R=1, S=1, both outputs Q and Q' are driven to 0.
Then, when you move to R=0, S=0, both outputs Q and Q' are driven to 1.
Then, because of the feedback, the outputs will go back to 0.  This
process will continue indefinitely, and it is called the 'race condition.'

I don't have an online reference to the circuit diagram of an R-S latch
and I don't think that I could do it with text in this email, but if you
want me to post this, let me know and I will see if I can scan in a
schematic.  However, the formulas that specify an R-S latch are:
Q  = R NOR Q'
Q' = S NOR Q

Sorry if this is not the race condition that you are referring to, but
this is the context in which I have heard of race.

Mike Lindahl
mlindahl@princeton.edu

On Wed, 21 Apr 1999, Michael Hicks wrote:

> I was wondering if someone could explain to me exactly what a 'race condition'
> is.  I've heard about it many times, but the context is usually weak and I can't
> quite figure it out.
> 
> Thanks..
> -- 
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