> >I would like to make a brief comment about hiding power pins.  I have
been
> >burned.  My advice to anyone who thinks this is a good idea is don't do
it.
> >Show everything where nothing is assumed to be connected.

I second this motion!

Which snake are you more likely to get bitten by:  the one you can see, or
the one that is hidden?

And so it goes with power pins.  When I create parts symbols, I always make
the power pins visible.  That way I can connect them to whichever power bus
I need to, and know that they are indeed connected.

The same goes for NC pins.  Show them, and use a no-erc symbol on them to
explicitly declare that "No, I didn't forget to connect it.  It's supposed
to be unconnected".

[Off topic]  I also hate assembly language code written with macros.  Same
concept (hidden code).  It makes it very difficult to figure out what's
really happening.

Best regards,
Ivan Baggett
Bagotronix Inc.
website:  http://www.bagotronix.com


----- Original Message -----
From: Abd ul-Rahman Lomax <[EMAIL PROTECTED]>
To: Protel EDA Forum <[EMAIL PROTECTED]>
Sent: Tuesday, March 13, 2001 8:39 PM
Subject: Re: [PEDA] Protel default Vcc hidden power pins


> At 06:36 PM 3/13/01 -0600, John Lemburg wrote:
> >I would like to make a brief comment about hiding power pins.  I have
been
> >burned.  My advice to anyone who thinks this is a good idea is don't do
it.
> >Show everything where nothing is assumed to be connected.  This allows
> >proper identification of all bypass caps shown right where they are
> >connected to the device.
>
> I routinely use hidden power pins without a problem. But I also know that
> it is easy to wander blindly into the world of hidden pins and get burned
> fairly badly. *If* there is a single hidden power supply on the board,
> *and* one has verified that the hidden pins have the appropriate
> attributes, there can be good reasons for using them. Ideally, when we
> design parts that might be candidates for the use of hidden pins, the pins
> are placed such that they can be unhidden and used with ease and grace.
Not
> all the Protel parts have been made this way.
>
> If one uses unhidden pins for power, with multigate ICs, as a common
> example, the question arises of where to put the power pins, i.e., on
which
> section or on all sections. Suffice it to say that this can be a nuisance
> in itself. How many times I have ended up with a mess because section
> numbers were changed for various reasons with a part with power on a
single
> section, I don't care to count.
>
> Something that I would try if I had time today would be to unhide the pins
> on one section of an IC with hidden power pins and connect that to a
> differently named power supply. I would expect this to generate an error
or
> at least a net renaming warning if other sections with hidden pins were
> present in the design.
>
> If so, and if one wants to be explicit, one could simply unhide one
> section, any convenient section, assuming that all the sections have
hidden
> pins, and wire it explicitly. This would be very safe. If one wired it
> explicitly to a different net than the hidden net, it would generate an
> error or warning.
>
> Thus one would have the best of both worlds.
>
> As to bypass capacitors, it is just as explicit to place a bypass cap with
> power objects next to the part in question, and it is easier to implement;
> one can do it for a whole page at once by placing one cap and its power
> objects and copying it as many times as necessary. Since it is not
actually
> going to a pin, the location is not critical.
>
> [EMAIL PROTECTED]
> Abdulrahman Lomax
> P.O. Box 690
> El Verano, CA 95433
>

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