Hi All,

I'm Not sure if my earlier post got thru but ..

Terry Harris wrote:

> On Fri, 27 Apr 2001 07:55:37 -0400, you wrote:
>
> >> Bottom line, the format is a netlist as we understand a net list plus the
> >> physical location and dimensions of the pads.

It is more than that. It  defines the location pads for of "say" U1 in X-Y
coordinates and rotation. As well as connectivity of the components in a given
net.
It also proves out plane hits. I know this because I have to manipulate
gerbers to make some boards due to Protels limited capablilities in this regard.

Ie, I have 3 ground planes and want the IC's to connect to all three but the
filter caps to connect to the core ground  only.

>
>
> I hope it isn't that simple - testers, particularly roving probe testers
> only test continuity from each end of a 'net' + any stubs. For testing
> non-continuity (shorts) they don't bother looking for shorts between nets
> which don't get close to each other. You need more than a netlist and pad
> locations to figure out net ends, stubs, and net proximity

This is confusing me. If they dont get close to each other how is it a short?

> .
>
> >>It looks quite simple to
> >> write; it would be much easier to generate this from the Protel PCB ASCII
> >> file than from gerber; all the necessary data is there in named fields,
> >> mostly in the pad records.

That is how the 3rd party software I use works.

>
>
> >So here is the scoop, a spectra dsn file contains everything-  all of the
> >pads, pad shapes, and netlist information, maybe one of you hotshot
> >programmers out there can convert the dsn file to a much needed 356 file

I don't have spectra. Can I generate this file From Sp5/6?

> .
>
> Much needed?

Yes it is Much needed.

>
>
> While Gerber is not an ideal format for generation of connectivity
> information at least it is a standard and one that PCB houses are going to
> get from all customers.

That is a MAJOR  problem. This File Needs to come fron the database
so it verifys the gerbers. I have been almost bitten and the D-356 saved me.

>
>
> If you choose to supply the board house with additional information then it
> is your problem if it is wrong - and you are going to be less familiar than
> the board house is with the conversion tool and less able to 'tune' it to
> suit their tester

Not if it is pulled directly from the database. The Gerbers can be wrong for
many reasons.

>
>
> I think it would be more useful to be able to check a conectivity netlist
> against a Protel design, the PCB house gives you the netlist generated from
> Gerbers the way they think they plotted them. That would check the
> connectivity netlist and Gerbers and check them before they have made a
> batch of possibly bad PCBs.

Yes this would work but... I have TOO much work as it is and I'm not getting
paid
to verify the Board houses work. I can Prove the IPC file does this and puts
the responsiblity in the board houses hands where it belongs.

Thanks for the input Terry. I am not trying to Jump on you, but my experience
has proved otherwise. Protel would be well advised to work on this as opposed
the simulation stuff as this could be used Now and it appears the Sim libs, etc
need
lots of work..

Regards,

Jim McGrath
CAD Connections, Inc.


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