# [SI-LIST] : RE:

obennig ([email protected])
Wed, 14 Apr 1999 14:20:21 -0600

Stephen

Thanks for the answer, do I need an end fork for every fork I use?

Otto

-----Original Message-----
From: Stephen Peters [mailto:[email protected]]
Sent: Wednesday, April 14, 1999 1:33 PM
To: [email protected]
Subject:

Otto Benning wrote:

> Hi
>
> I am using IBIS 3.0 and the question is
>
> I am trying to model the circuit board traces of a memory board
> how do I model forks in side of forks
> example
>
> Fork
> Len = 20
> Fork
> Len =30
> Endfork
>
> or
> are they just separate forks, no matter how many times the traces
> has forks in it.
>
> example
> fork
> Len = 20
> Endfork
> Fork
> Len = 30
> Endfork
>

The first example describes a trace (of Len=20) that branches (forks) from
some unspecified main trace, then a trace (of Len=30) that forks from the
previous fork:

main trace -------------------+------------------------
|
|
Len=20 at this point +-------------------- (Len=30)
|
|

The second example describes two forks (one of Len=20, the other Len=30)
that branch from the same point on an again unspecified main trace -- in
other words, a 'Y' or 'V' type structure.

The general algorithm for producing this kind of tree diagram (there is some
formal name for this style of topological description but I can't think of
it off hand) is:
1. Start walking down a path
2. If a branch (fork) is encountered, then branch from this main path.
3. Walk down the branch until a matching endfork is encountered.
4. Return to the main path at the point at which the fork occurred and
continue
tracing the main path.

Of course, while is step 3, step 2 can be called recursively. I hope this
helps.

Regards,
Stephen Peters
Intel Corp.

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