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Message
From: John Sheahan <jrsheahan@o...>
Date: Tue, 29 Apr 2003 07:31:29 +1000
Subject: Re: [oc] Async reset: active high or active low?
On Mon, Apr 28, 2003 at 05:24:40PM +0200, cyrano@n... wrote:
> I really ask why active low reset is used in our labs. It was answer that it is an historical raison because in TTL high level signal consumme less energy than low one. Power up is not concerne any more because logic begin to work at ~2.5 V.
this is wrong. TTL inputs (real ttl, not this newfangled LS
rubbish :) drew about 1.4ma when low and and few hundred microamps
high. So an active low reset minimized power.
(note that using minimize power and TTL in the same sentance is tricky)
Also the (off) noise margin was much better for active low signals.
john
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