On Feb 19, 2009, at 3:25 PM, Yamazaki R2 wrote: > > Here is an annoyance I'm experiencing often when it comes to > gschem. > When I instance an symbol in, whether it be a transistor, a > subcell, > or any other random component, all of the attributes are saved > in the > schematic file instead of inherited from the symbol file. This > may not > seem like a huge concern but imagine that you have a fairly large > hierachrical design where you instanced transistors in from a > symbol > file 100's of times. Lets say the symbol properties of that > symbol are > refdes=M?, l=0.13u,w=1u,device=n3t,bulk=vss,value=n. Now, I > bring in a > new model for that transistor called nmos instead of n. So I go and > change the symbol file from value=n to value=nmos. But whoops, the > attributes are local so now I have to open up every schematic and > changes the transistors one by one instead of editing on symbol > file > and having my whole design inherit the attributes. > Now with that said, I know inheriting ALL attributes wouldn't > make any > sense. For example you can't have the refdes and w/l inherited.
You might want your most common w/l inherited. Doesn't hurt. > However, there should be some way in the symbol file what to > inherit > something by default and making the local version optional. I generally use (always-promote-attributes "") in gafrc. That stops most attribute promotion, but refdes and symversion still make it. Then, you inherit attributes unless you override them by attaching something. > For > example the way other CAD tools I know of handle this is that each > instance has a master attribute and a local attribute. If there > local > attribute is blank, it inherits from the master attribute. If the > local attribute is filled out, then it takes that value of the > master. > refdes should me mandatory, all else should be optional. And that's essentially what I get. That makes the project symbol directory really useful. "low_speed_opamp.sym" is what the project needs, and if I change it I don't need to edit dozens of instances. John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ [email protected] _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
