Re: gEDA-user: Implicit terminal question

[Bill Cox <bill@viasic.com>]

Sribalan Santhanam wrote:

> Hi
>
> I just downloaded and installed the gschem tool suite.
> I'm playing around with it and and impressed with whats
> Been done so far. Great job!
>
> I do have two dumb/simple questions?
>
> 1. Is this the right forum/user group to address user questions
>   about the tool. Is there a newsgroup that I can read to 
>   look at archived questions if my question is already asked/answered?
>  
I think so.  The archives are available on the www.geda.seul.org site.

> 2 I just created my first symbol. A 3 terminal NMOS_TRANSISTOR and
> I ran into 2 issues.
> A) I'd like the 4th pin (the bulk) to be an implicit connection to
> ground.
> To do this, I simply added a net=vss:B attribute in the nmos.sym.
> However, when I gnetlist (spice or spice-sdb) the schematic I
> instantiate this symbol
>  
Assuming you're doing a CMOS IC design, you may want to use the spice 
netlister I've put into the 'gdatabase' tool.  It connects the base 
based on just this attribute.  In addition to dealing with this issue, 
I've also added some support for busses, hierarchy, and instance arrays. 
I'm the first user of this tool, so if you do use it, you might be the 
second, so you'll probably find some bugs.  I'll fix them quickly if you 
do.  There are a set of symbols I'm using to design my chip, including 
nmos and pmos devices, in the gdatabase/batch/test directory of the 
gdatabase source.  The source is on 
www.viasic.com/download/gdatabase_20031107.tar.gz.

> In, I get the following line in the netlist.
> 	M1 out in vss ERROR_INVALID_PIN
> Am I approaching this incorrectly? How should I handle implicit
> connections to pins?
>
> B) Whats the recommended method of passing device parameters 
>  (like area of source/drain) to transistors. Currently, I'm
>  creating new attributes "as", "ps" etc and things see to 
>  work but I figured there may be a better way. 
> /sri  
>
>
>  
I think this is the correct way.  The gdatabase spice netlister knows 
about the parameters each device can take, and only spits out the 
corresponding attributes.

Bill