Global nets

[Jason D. Bakos]

Hi everyone!

Does anyone know if there is any way in Virtuoso or Affirma to define a
net as being global? Any other words, when Affirma generates a netlist,
what tells it that certain nets such as vdd! and 0 need to be declared
as global? I need a way to trick Affirma into adding additional
netnames to the 'global' statement in the header of the netlist file.

Thanks!
-Jason

 

[Andrew Beckett]

Jason,

What tells it is if a signal in the database has the isGlobal attribute set.

cv=geGetEditCellView()
sig=dbFindSigByName(cv "gnd!")
sig~>isGlobal ; returns t if the signal is global.

Now, there is a convention where global signals end in !, and so
Composer will look for nets which end in !, and mark the corresponding signals
as being global. However, you can make any signal global in SKILL, but be warned
that Composer may stomp on this again when you check-and-save (actually, just
check) the cellView.

Note that in various ADE netlisters, gnd! is mapped to 0 to follow the SPICE
convention of node 0 being the global ground.

So if you want to "trick" ADE into netlisting other signals as global, you can
do:

a) create a net in the schematic, labelled fred! - this won't be tricking
anything, it will create a global signal called fred!
b) Fiddle with the isGlobal attribute on a signal in the database. Note,
you'll need to ensure that the lastSchematicExtraction date is greater or
equal to the instancesLastChanged attribute on the cellView otherwise
the netlisters won't netlist the cellView as they'll think it is changed
since the last connectivity extraction (which of course it is...)

Andrew.

On Mon, 09 Aug 2004 16:38:12 -0400, "Jason D. Bakos"
<jbakos@cREMOVEs.pitMEt.edu> wrote:

Hi everyone!

Does anyone know if there is any way in Virtuoso or Affirma to define a
net as being global? Any other words, when Affirma generates a netlist,
what tells it that certain nets such as vdd! and 0 need to be declared
as global? I need a way to trick Affirma into adding additional
netnames to the 'global' statement in the header of the netlist file.

Thanks!
-Jason

--
Andrew Beckett
Senior Technical Leader
Custom IC Solutions
Cadence Design Systems Ltd