Thanks for the tips.
My SO14-SO16W has short track segments between the equivalent pads -- maybe
this causes the DRC problems.
I was unaware of the function of Design/Netlist Manager/Menu/Update Free
Primitives, so I'll look into it.

Damon Kelly
R&D Engineer

Blastronics Systems and Services
Infratech Systems & Services
...business units of:

Texcel Pty Ltd
PO Box 3699
South Brisbane, QLD 4101
AUSTRALIA

24 Bank St
West End, QLD 4101
AUSTRALIA

Ph  +61 7 3237 8109
Fax +61 7 3237 8188

> -----Original Message-----
> From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]]
> Sent: Friday, 21 December 2001 08:25
> To: Protel EDA Forum
> Subject: Re: [PEDA] Dual Footprints
> 
> 
> At 08:48 AM 12/20/01 +1000, Damon Kelly wrote:
> > > If you want one footprint that can except two different
> > > devices you can
> > > do that with a special footprint (named ssop14-ssop16??).
> >
> >This option causes DRC errors - or at least it does in my 
> implementation. I
> >sometimes require an SO-14/SO-16W footprint, to allow 
> alternative op-amps,
> >and I always seem to get DRC errors of the type "extra pads 
> on net" etc...I
> >can live with them, but it's irritating.
> >Is there anyway to prevent the DRC from tripping over the extra pads?
> 
> Last time I looked, Protel does not generate a DRC error for 
> pads where the 
> pads have the same name. If one of the pads has no name, it 
> will create a 
> DRC error. However, in either case, track connecting the 
> pads, if it is 
> part of the footprint, will create short errors until the 
> track is assigned 
> the appropriate net, either as part of the synchronization 
> process or using 
> Design/Netlist Manager/Menu/Update Free Primitives.... -- which also 
> updates component non-pad primitives. Technically, this is a 
> minor bug, but 
> we use it.
> 
> To summarize, there are three ways to handle double-padding:
> 
> (1) Place two symbols on the schematic with a note that only 
> one of them is 
> to be inserted. If the two symbols are placed on top of each 
> other, the 
> note may not be necessary. Name one of them, for example, 
> U14A, the other 
> U14B. Each one of these may then have its own footprint. 
> There will be two 
> separate components on the PCB, they can be placed in any 
> arrangement that 
> works.
> 
> When one symbol is placed atop another, one may wish to hide 
> some of the 
> various text displays....
> 
> (2) Use a single symbol on the schematic but place a 
> double-pad pattern on 
> the PCB. This footprint has two pads for each original 
> schematic pin. Each 
> of these pads will have the same name. If the Synchronizer is used to 
> transfer net information, the pads will be properly assigned 
> nets; if track 
> or other primitives are added, Update will be required. If 
> Load Netlist is 
> used, there is still a bug which can cause assignment oscillation.
> 
> (3) Create a schematic symbol with double pins. I won't go 
> into detail on this.
> 
> Protel does not support multiple components with the same reference 
> designator. It will cheerfully allow you to create them, but 
> it does not 
> properly handle net assignments. I can see arguments for 
> leaving it this 
> way, but it could also be argued that allowing multiple 
> components with the 
> same refdes (and which would be assigned identical nets) 
> would be useful 
> for double-padding. On the other hand, a single footprint for 
> double-padding is schematic-controlled and thus will survive 
> synchronization with unused component removal, etc., and I think it's 
> better to leave it as-is.
> 
> Protel does not seem to support free primitives in Unions. If 
> it did, this 
> would provide another solution to this problem (though Update 
> would still 
> be required); one could simply add pads and create a union with the 
> original footprint. Free primitives in Unions would be useful 
> for other 
> reasons. My guess is that they did not do it because it would 
> have added 
> another field to all the primitives, whereas component Unions 
> only involved 
> the component primitive, not all its parts. Maybe next release.
> 
> 
> 
> 
> [EMAIL PROTECTED]
> Abdulrahman Lomax
> Easthampton, Massachusetts USA
> 

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