Carlos Nieves Ónega wrote:
Hi Dan,
El jue, 02-03-2006 a las 16:09 -0500, Dan McMahill escribió:
[snip]
I'm generally opposed to using "special" netnames. I've managed to jump
in here late in the discussion, but it seems to me that you shouldn't be
connecting your schematic up as a short.
Don't forget, you have 26 other backends besides the PCB backend.
Was this just to keep drc2 from complaining about unconnected pins?
If so, perhaps we can come up with a better no connect symbol which
doesn't use a fixed net name.
If you have unconnected pins and you don't use the DRC, it's all ok. If
you want to use the DRC, you should have some way to tell it that you
really want to leave a pin unconnected.
I've seen several approaches to this:
- Use a special no connect symbol. Currently there is such symbol in
gschem, which connects that pin to a net named "NoConnection".
- Another approach here would be that gnetlist don't add that pin to
the netlist (it can know it is a special symbol), but then the DRC won't
be able to check it.
- I've also seen some DRC markers so the DRC don't check a given net,
but this situation would be like the previous options.
Clearly if you're driving a spice simulation you want the net to be
given a unique name and have it show up in the netlist even if it
doesn't connect anywhere else. For example, you may have a subcircuit
where you're not connecting anything to one of the outputs but you want
to be able to plot the signal there.
In fact, right now if you use this no connect symbol, you'll actually
short out everything in the spice netlist too unless thats also updated.
I suppose the problem is if we simply get rid of the net connection in
the no connect symbol, we'll have a problem where various backends will
try to netlist it.
What would be nice is if attaching a no connect symbol could attach an
attribute to the net to indicate that a single connection is ok but
otherwise act as a graphical symbol which is ignored globally by
gnetlist. Then other backends won't have problems and drc2 can key off
of a net attribute.
-Dan
