RE: gEDA-user: Spooky Action . . at a distance!

["Mark Cianfaglione" <mark_cianfaglione@xxxxxxxxxxx>]

Samuel

Pretty scarry actually. I can't tell you how many designs I've seen in my
career that I've seen that "flaw" one or two of which had been been in
production for a while and the customers were complaining about random
events. I personally make all the pins for my devices present on the
schematic for that reason. I'm not a fan of the "hidden power pins" type
symbols for that reason. I'd rather have an "unsightly" schematic with all
its power pins and decoupling caps near the logic to prevent such a problem.
It also allows other people to review without having to assume that the
power is connect up properly...

At least this is not only a gschem issue... It happens to a lot others as
well.

Mark



-----Original Message-----
From: owner-geda-user@xxxxxxxx [mailto:owner-geda-user@xxxxxxxx] On Behalf
Of Samuel A. Falvo II
Sent: June 7, 2005 3:09 PM
To: geda-user@xxxxxxxx
Subject: gEDA-user: Spooky Action . . at a distance!

OK, I just had the *weirdest* experience of my life.

Spooky.

I am working on wiring up the IPL circuit as documented at
http://www.falvotech.com/projects/kestrel/repo/8k/prints/ipl-port_3.pdf
.  I plugged power in, and I ran the software on my Linux box to
program it (wrote it myself; sources coming soon).  I probed around
with the o'scope, and everything was working.

Perfectly.

Shortly afterwards, I noticed that Vss of U301 was not hooked up to
anything!!  Vdd was connected to +5V, as expected.  And yet, it worked
fully.

Anyone else ever have something like this happen?  I know this is
pretty much just a fluke, but I'm wondering *why* it worked?

Anyway, I hooked Vss back up, and the circuit operation didn't change
at all.  :-)

-- 
--
Samuel A. Falvo II