Re: Pspice compatibility: Bus representation in subcircuit calls

mostly from Jim:

>>
>> We still seem to be running in circles.  In my mind schematic capture
>> must be able to do the following things:
>>
>> (1) Create a netlist readable without ambiguity by the Spice engine.
>> (2) Yet present a useful visual representation of the circuit...
>> humanly readable; AND handle hierarchical and bussed designs.
>> (3) Have a user-friendly GUI to make drawing convenient.
>> (4) Allow placing "markers" on the schematic that then show waveforms
>> in an appropriate viewer.

I agree, except for this.  I find it unnecessary.  This is simply
preference.

>> (5) Show operating point data (voltages and currents) directly on the
>> schematic, for debugging, if desired.

I miss this.

>> (6) Be able to produce LVS netlists in formats readable by many layout
>> tools.
>>
>> PSpice Schematics can do *all* of the above ;-)

Except I don't believe it does iterated instances, does it?  If you
don't do large arrays, you don't need it.

I got used to the Cadence Edge program years ago which I think was a
lot better than the current Opus or whatever.  At any rate, I looked
for pc based software that had the key features I used in Edge.  I
like the way Cohesion deals with arrays and busses (just like Edge
basically).  

It's possible to make an 8k x 8k array of cells with 3 levels of
schematics: one for x, one for y, and the cell itself.  The bus
structure lets you connect a unique line to each cell for addressing
and at the same time connect a single line shorting all the cells for
power and common row or column select lines.  In 6.0, they improved
the bus structures to allow an intermediate breakout and reconnect
between busses.

You can also highlight a node at the top level and follow it up and
down the hierarchy to verify connectivity.  I used this a lot on large
chips in Edge and still use it in Cohesion.  The limitation is that in
Edge, each successive node selected would be a different color.  In
Cohesion, all selected lines are  the same color.  

I use names and globals a lot for connectivity to simplify schematics.
This highlighting can really help spot a misspelled node.

[LTspice schematic will also highlight a node, but seems to only
highlight a single node at a time.  Highlighting the next node seems
to deselect the previous one.  I didn't find a way around this.]

Archiving is another important feature I like.  Cohesion allows the
user to set up libraries anywhere they want.  There's a master.ini and
a local.ini to set up pointers to these libraries.  At the end of a
design, I archive everything to a single directory for storage.
Otherwise schematics become useless as libraries change.  Cohesion
will also archive the executables so that you can always open the
schematic without invoking the main software.  I send these archives
to customers along with the gds at the end of a job as part of the
documentation.

I've used Cohesion for a decade in it's various forms as
ECS/Synario/CohesionTools.  The guys are friendly and great to deal
with.

It's is a viable work-around if you lose Pspice Schematics eventually.
It will output a Pspice compatible deck with all the trimmings. .  If
you select {} for busses, pspice runs, but may or may not allow you to
look at these busses in probe. (Probably not, since Pspice schematics
loses the brackets. )

Since Cohesion is a separate schematic capture, it won't back annotate
or cross probe with Pspice, though I understand the code is there on
the Cohesion side to do this.  If you need this, you'll have to look
elsewhere.

http://www.cohesiontools.com/

Another program I've been looking at is Smash from Dolphin:

http://www.dolphin.fr/medal/smash/smash_overview.html


Smash started out fairly economical, but has gotten more and more
expensive.  They started with the Cohesion 5.1 schematic capture, but
recently are offering an additional alternative I haven't seen.  They
back-annotate, cross probe and all that stuff as I recall.  They are
French, though, so the culture is different.  I'm told they can be
hard to deal with.  That must be after the sale though, because I've
never seen this.  I have friends that use Smash that really like it.
They use the vhdl front end to control analog sims in large mixed mode
designs.  

>
>That is a good list.  I certainly hope I never
>implied anything in contradiction to it.  My own
>focus was on it "(1) Creating a netlist readable
>without ambiguity by the Spice engine", and then
>differentiating that from the SPICE engine itself.
>

Regards,
Larry