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From: mouth@ibm.net (John Kelly)
To: Michael Smith <msmith@atrad.adelaide.edu.au>
Cc: msmith@atrad.adelaide.edu.au, freebsd@atipa.com, hackers@FreeBSD.ORG,
        terry@lambert.org
Subject: Re: Sharing interrupts
Date: Wed, 30 Jul 1997 09:05:47 GMT
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References: <199707300848.SAA21116@genesis.atrad.adelaide.edu.au>
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On Wed, 30 Jul 1997 18:18:14 +0930 (CST), you wrote:

>I would avoid the use of silicon power diodes for this application;
>they have a significant parasitic capacitance, and will generate a
>substantial spike on the ICU input when your device signals an
>interrupt.  They also have a long Toff (turnoff time), meaning that
>when your device drives the interrupt output low you will generate
>another spike and considerable ground noise.  They also have a very
>_substantial_ voltage drop at low current, certainly not "minimal".
>
>If you must use a large diode, use a "fast-recovery" type such as a
>UF4001; ideally, you should be using a fast small-signal diode like
>the (very cheap) BAT-47.  This device also has a much lower Vf(max),
>around 0.4V, and very low parasitic capacitance.

More interesting points.  Thanks for the heads-up.

John