Re: gEDA-user: Hierarchy question

[sdb@cloud9.net (Stuart Brorson)]

> 
> Hi.
> 
> I can now read schematics and symbols into a temporary set of data 
> structures, and build nets.  I'm working on writing the data structures 
> to the netlist database.

Cool!

> How do I know what the top level pins for a schematic are?  I need to 
> build a default symbol for the top level.  The use of flags makes sense, 
> but the IO symbols don't seem to make much use of the device attribute. 
>  I don't know how to tell what's a flag.  How can I tell?

I created a symbol for the IOs in a SPICE .SUBCKT.  The symbol is
called spice-subcircuit-IO-1.sym or  something like that.  It lives
in the sym/spice directory.  You can take a look at that -- it may
give you some ideas.

As for the default symbol for the top level, I also created a symbol
called spice-subcircuit-LL-1.sym, which you are supposed to place on a
.SUBCKT schematic when you are creating a SPICE .SUBCKT to embed in a
larger project.  It causes the netlister to barf out the 
".SUBCKT X Y Z Name" SPICE card at the head of the .SUBCKT deck.  As
far as I can tell, this way of identifying hierarchy works for people
when creating circuits to model with SPICE.  Perhaps this is close to
what you want? 

> I'm thinking that flag symbols should set their device attribute to 
> something like FLAG or IO.
> 
> Thanks,
> Bill
> 
> 
>