RE: True or False?

Chris,

1) Could you please point it out to me where the spec says that it is NOT
allowed to have anything, except terminators on either side of the series
device? I don't recall reading that, but might have missed it.

2) Our device which has this situation actually does sense the signal
differentially, but since it never drives and the clamps are so far out from
the
signal swing, we didn't include a receiver model (even though I was
considering
to do it).

3) It may be sufficient to define [Series mapping] only if we didn't have a

receiver in the device.

Since we just made an IBIS model like that, you got my curiosity up, is it
really illegal to do this? By the way, it passed the parser, so if it is
illegal, should the parser check for that?

Arpad
============================================================================
===

Arpad,

The Spec explicitly does NOT allow either side of the series device to
be anything except terminator. So how can you have a differential
relationship (such as vdiff, or tdelay) between terminators (there's
no sensing nor driving)? I argue that if that component is not
sensing the voltage difference on those pins then from the point of
view of that component, the pins are not differential.

Note that if you want the nets to be connected differentionally, this
would occur at a another component(s) on the board which would have an
actual differential driver or receiver pair triggering an electrical
association between the nets.

   I+ ---series--- O+

   I- ---series--- O-

Would it be sufficient to define the [Series mapping] only and not the
[Diff Pin] relationship for the above case?

Chris

>
>
> I would vote for FALSE, because I could see them being used together in a
> situation where you have a differential pair going into the chip and come
> out on
> two other pins though a series model. For example, let's make
>
> pin2 = diff_in+
> pin3 = diff_in-
> pin4 = diff_out+
> pin5 = diff_out-
>
> where the ins and outs are "shorted" with metal.
>
> In this case the [Diff Pin] keyword would associate pins 2-3 and pins 4-5
as
>
> differencial, but the [Series Pin Mapping] keyword would connect pins 2-4
> and
> pins 3-5. Since the series models ignore the C_comp, the only way I can
> enter
> the die capacitance into this picture is if I use the Terminator model on
> each
> pin with nothing but C_comp in it.
>
> This is how I can see the series and terminator models used together with
> differencial pins.
>
> Arpad
> ==========================================================================

>
Received on Thu Oct 8 12:02:24 1998