My experience with split planes in 99SE is that it doesn't work if you
autoroute the board.

I had a design about a year ago that I was initially going to use split
planes on (3.3V and 5V nets on the same layer).  After placing the split
planes, using the autorouter would result in the 3_3V and 5V pins being
connected to an *arbitrary* location in the split plane layer.  Sometimes a
3_3V pin would connect to the 5V plane, and vice versa.  Some of the power
vias would even straddle the boundary between the 2 splits, shorting them
both together.  I can't recall if DRC found this error, I think it did.  But
that really really sucks, when the autorouter won't obey a DRC rule, and
that negates the usefulness of split planes.  So I ended up not using split
planes, and going to an 8-layer PCB instead of 6-layer.  Chalk this up to
one more Protel hype-feature that doesn't really work!

Software industry motto:
1) Programming is for programmers
2) Product design is for marketing
3) Testing is for users
4) Big pay is for upper management

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


----- Original Message -----
From: "Harry Selfridge" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Thursday, July 03, 2003 12:59 PM
Subject: [PEDA] Nested Splits (Was - disappearing split planes)


> Steve -
>
> I know what it says on page 596 of the designer's guide, but you should
try
> an experiment yourself.  Define a plane as VCC, put a rectangular split
> VCC1 in the center of the plane, put another rectangular split VCC2 inside
> of that.
>
> You will find that nesting split planes works just fine.  We have done
> variations on that kind of nesting in several hundred designs without
> problems.  Perhaps the designer's guide was based on some variation of
> Protel99 before it evolved into Protel99SE+SP6.  If you should find a
> situation where it doesn't work - please let me know.
>
> Regards - Harry
>
>
>
> At 10:50 AM 7/3/03 +0100, you wrote:
> >03/07/2003 06:00:02, "H. Selfridge"
> ><[EMAIL PROTECTED]> wrote:
> >
> > >As an aside - there is no problem or prohibition regarding
> >nested split
> > >planes.
> >
> >Yes there is - page 596 of the manual you linked to - that picture
> >is an explicit ban on nesting split planes - you can wrap sausages
> >of planes around islands, but you can't put islands within islands.
> >The cleanup you have to do in the gerbers to close the sausages is
> >annoying and (as evidenced by my mistake last week) error
> >prone. I do wish Protel could just do this properly - does DXP?
> >
> >Steve
>
>
>



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