[SI-LIST] Re: SpecctraQuest
- From: "Todd Westerhoff" <twester@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 24 Jul 2001 13:06:01 -0400
Greg,
You're correct - everything needs to be "placed" for SPECCTRAQuest to
extract a topology successfully. There are two reasons for this:
- until at least one copy of each component type is "placed" (in the Allegro
sense, more on that later), the part data for the component doesn't even
exist in the Allegro/SPECCTRAQuest database. Allegro/SPECCTRAQuest read the
part library and "import" the part data into the database when the first
component of each unique type is placed.
- SPECCTRAQuest wants to be able to determine a length for all line segments
when extracting. If the part isn't placed, there's no length to determine.
While it's true that the tool could just assume a length for unplaced
components, it doesn't.
"Placed" in the Allegro sense, means the component has been placed anywhere
in the design. It *doesn't* have to be inside the board outline.
As far as test points go, the issue is SPECCTRAQuest's ability to know what
to do with them, and that depends how they get implemented in the Allegro
database. There are different ways to create and manage test points. My
preference is to treat test points as single pin devices, which have an
associated signal integrity model having the correct parasitics. That
approach requires having the test points in the schematic, though, and
having the correct symbol/component correspondances into the schematic/PCB
databases. I can't speak to the other options in detail, as this is the one
I'm most familiar with.
Hope that helps,
Todd.
Todd Westerhoff
SI Engineer
Hammerhead Networks
5 Federal Street
Billerica, MA 01821
twester@xxxxxxxxxxx
ph: 978-671-5084
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Greg Letchworth
Sent: Tuesday, July 24, 2001 12:11 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] SpecctraQuest
Hello,
I had a question concerning the extraction of a
topology into SigXp. It is my understanding that in
order to examine a particular net, all components
associated with that net have to be placed in
SpecctraQuest. I understand how SigXp handles
discretes, IC's(with or without existing IBIS models),
and IO's. What I don't understand is how to handle
functional testpoints. What I mean by functional
testpoints is probing points for a lab scope for
critical nets, i.e. clocks. What does SigXp consider
them as; they aren't a 2 pin device like discretes,
nor do they have a driver or receiver like IOs, ICs.
Is there a special model I need to assign?
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