Abd ul-Rahman Lomax wrote:

>
> The "multilayer" layer causes all kinds of problems. For example, vias live
> on "multilayer," intrinsically. But blind and buried vias are most
> certainly not on every copper layer. As as result of how Protel treats
> "multilayer" and vias, one cannot get a true, simple, single-layer display
> showing only the blind and buried vias present on a particular layer. It's
> a mess. The only way to correctly view it -- as far as I know -- is to
> generate the gerber and then view it with a gerber viewer or import it back.

Yup, this is really a holdover from before blind and buried vias, and
shows a lack of thinking through all the ramifications of a change to
the software.

> If it is imported back, presumably after removing everything but those
> vias, I can turn off "multilayer" and see the pads that will then exist on
> the appropriate layers. But then it will be a pain to edit, as well as
> increasing the file size.
>
> Basically, multilayer should go. Instead, there should be a button that
> enables all copper layers. Or perhaps "multilayer" should stay, but not be
> necessary. In other words, pads and vias will display even when multilayer
> is turned off, if they exist on the enabled layers.

Yes, that sounds like the correct direction.  The only real purpose for
a multilayer-like pseudo-layer might be to have a drill display.  It would
show holes not only in pads and vias(where they are pretty much shown
ON the pad or via already) but on the inner planes (both power and
inner signals) where through holes that don't have isolation or thermals
on the power planes do not show at all, and where holes that pass through
without connection on signal layers also do not show.

But other than the above little idea for the holes, I don't see multilayer
as having much purpose anymore.

> I thought that Protel worked this way, but I could not get P99SE to do it.
> If I wasn't so busy, I'd go back and see what Protel 98 did with this.
>
> (In other words, if you had "top layer" enabled, you saw pads and vias in
> the top layer color instead of the multilayer color. As it is in P99SE,
> they aren't in the display at all, only *surface* top layer pads display.
> As far as P98 is concerned, maybe my memory is incorrect.)
>
> Technically, this too is a bug. If you have "top layer" enabled, you should
> be able to see everything on the top layer....
>
> It only becomes a serious bug when one is trying to do complex blind and
> buried via work. As it happens, that's my job at the moment.... grrr....
> The saving grace is that Protel will cheerfully route over those spuriously
> displayed vias. And the plots are correct.

The idea that (surface) pads display in one color, through holes in another,
and vias in still another is generally workable, and of use.  It gets a little
more blurry with blind and buried vias. (ie. do you have different colors for
blind and buried vias on different layer combinations - what about a
blind and a buried on top of each other?)

A simple fix would be that pads and vias show in the layer's color when
in single layer display, but in the special identifying color when in multi-
layer display mode.  This would than make single layer look a lot like looking
at the gerber files.

Maybe Protel should only draw a pad or via if it is on a displayed layer,
unless multilayer is turned on.  That would make a lot of sense.  It would
also work very much like the current program, except when blind and
buried vias are used.

Jon

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