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Date: Tue, 11 Feb 2014 11:27:37 +0100
From: Gabriel Paubert <paubert AT iram DOT es>
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Subject: Re: [geda-user] How to identify nc pads in tsym files
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On Tue, Feb 11, 2014 at 10:24:34AM +0100, Richard Hughes wrote:
> On 10 February 2014 15:15, Gabriel Paubert <paubert AT iram DOT es> wrote:
> > On this kind of package, typically the center pad is some kind of
> > ground/power. It's a bit surprising that you call it "signal", but
> > we've seen strange things.
> 
> It's a bit of a strange chip:
> http://www.mazet.de/en/english-documents/data-sheets/mtcsicf/download
> 

Thanks, at least the nc are really nc, that's quite explicit in
the doc on page 6 ("The NC pads on PCB could be used for PCB layout 
routing) and on figure 6 on page 9, where it is actually ground, 
although I could imagine applications where you want to have the
backside at a floating, albeit stable, potential.


> > Otherwise you can always explicitly show these pins on the symbol
> > and connect them to the net that goes to the center pad.
> 
> Yes, I thought about that, but that means if I upload the symbol then
> someone might get confused they *have* to use this pin. Seems a bit of
> hack, but it's the favourite so far.

Do not try to cater to the people too dumb to read a datasheet!

Personnally I'd give the net that goes to VPD a name, say VPD, 
and add a net=VPD:1,2,3,4,6,7,9,10,11,12,14,15 (or a subset of 
the list if I don't route through all the nc pins).

This makes the symbol smaller (5 pads instead of 17 and space
is always at a premium on schematics, or is it just me?), 
its shows only the important connections on the schematics 
and is easy to edit. 

	Gabriel