RE: [PROTEL EDA USERS]: PADS ASCII netlist reference designator bug - is there a workaround?

[Abd ul-Rahman Lomax <marjan@vom.com>]

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At 08:05 PM 9/9/00 -0700, Drew Lundsten wrote:
>My problem is not with the PADS limitation of 16 characters for ref des,
>it's with the Protel limitation of 7 characters. A reference designator of 8
>characters will not export correctly to a PADS ASCII netlist.

Yes. I would speculate that the Protel PADS netlist format was written to 
be compatible with an older version of PADS, though I don't know that for a 
fact. If this is true, if Protel "fixed" the problem, the Protel PADS ASCII 
netlist output could cause problems with older versions of PADS.... What 
would be necessary would be to create a new netlist output format.

>Protel exports the Protel netlist correctly because it adds a newline after
>the reference designator. The reason we have an 8 character ref des to worry
>about is that the ref des reflects the schematic sheet number (3 digits) as
>well as subassembly module (3 digits) for identification on the BOM and in
>DVT. Our only workaround so far is to convert the Protel netlist to a PADS
>ASCII format, but that means maintaining another piece of scriptware.

There can be situations where almost anything is appropriate, and I can 
appreciate that a company may be locked into a system, but this strikes me 
as a serious abuse of reference designators. Normally, a reference 
designator appears on the PCB in the silkscreened legend. It would be very 
common that there would be no room for such a long designator as described. 
Subassembly module number will be found on the BOM, on the PCB or assembly 
drawing, and thus, I would think, this information is redundant.

Reference designators are normally keyed to the BOM and schematic and carry 
no other information other than general part type (U, R, K, etc). Thus a 
six character reference designator will accomodate a two-character standard 
prefix (these prefixes are the subject of an ANSI standard) plus four 
digits for numbering, and it is very difficult for me to conceive of a 
printed circuit board with more than 9999 instances of a particular kind of 
part. So seven characters must have seemed enormous to the original writers 
of these programs. Of course, sometimes we like to do little tricks like 
labelling test points with the name of the net assigned to them, and there 
are plenty of designers who like to use reference designators, at least 
occasionally, that are more descriptive, like "EPROM23."

There is another string primitive in Protel, the "Comment", which can be 
made visible on the silkscreen, and this string, if desired, could carry 
the kind of information described. This could also correlate with what goes 
onto the BOM.

I'd think that PADS would have a similar facility.

>I can accept that Protel may not be concerned with exporting PADS ASCII
>netlists beyond 7-character reference designators, or at all - after all,
>why should we perform schematic capture in Protel and switch to PADS for PCB
>(other than the $20k investment in PADS). I was curious, however, to see if
>anyone else has run into this and found a workaround.

Mr. Lundsten has already found the workaround: an easily-written utility 
that does netlist conversion from the regular Protel format netlist to what 
he needs. But it might be better to look at the system that has such an 
unusual requirement, and give a little thought as to whether or not it 
could be improved by going to something more standard. I can easily see why 
one might want to have the schematic page readily accessible, but there are 
other ways to accomplish this. For example, an index of refdes-to-page 
added to the schematic. Protel schematic already will generate this as a 
report....

Once in a while, a strange ("innovative") way of doing things is better 
than the ways that designers have worked out over the decades. But not very 
often.

marjan@vom.com
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433



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