David,

A newbie addition to this question.  What should the unused pins be =
"tied" to.  Ground???

Thanks,

Ken Crismon

-----Original Message-----
From: David Duffy [mailto:david@AUDIOVISUALDEVICES.COM.AU]
Sent: Wednesday, August 28, 2002 6:25 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: Unused pins


At 08:00 PM 28/08/2002 -0400, you wrote:
>In a message dated 08/28/2002 19:46:38 Eastern Daylight Time,
>bmoran@MILLENNIUM.CA writes:
>
> > That's what I *have* been doing, but since I'm committing this =
project to a
> > PCB, I want it to be done right.  And I know that if the pins are =
ignored,
> > then there could be some issues with power consumption. CMOS is =
worse than
> > TTL for this.
> >
>
>Brendan, I've made a lot of PC boards where I ignored the unused pins.  =
Power
>consumption was really never an issue because I was always running of a =
wall
>wart.  Even so, I can't imagine that the power consumed by an unused =
pin
>would be significant.  And I have followed the same procedure with the
>"other" micro-processor.

Hi Sid,
It's not the power consumption as such, but the whole chip can oscillate =
and
behave badly when you let inputs float. It's just like leaving unused =
inputs on
CMOS gates floating - just asking for trouble. They (CMOS) have a habit =
of
latching up, heating up and dying. The increased power consumption is =
just a
symptom of the problem and should not be ignored.
Regards...
___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: www.audiovisualdevices.com.au
___________________________________________

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