[SI-LIST] Re: IBIS Model error
- From: "Jon Powell" <jonpowell@xxxxxxxxxxxx>
- To: <chris.mcgrath@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 17 Nov 2003 08:49:26 -0800
Chris,
you should go take a look at the IBIS spec to make sure I am right about
this but....
One of the problems we had when we were writing IBIS was trying to condense
many corners (fast, slow, hot, cold, big, little, etc) into just 3. I don't
remember why we chose 3 when it would have been just as easy for us to
choose N, but we did. So there. Anyway, I think we decided that MIN was fast
and MAX was slow (in general) and there are recommendations in the IBIS spec
on how to achieve this.
But I do agree that TYP should somehow be in between MIN and MAX.
jon
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chris McGrath
Sent: Monday, November 17, 2003 8:29 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: IBIS Model error
Speaking of IBIS model problems...
I have a model that has a couple of odd parameters that are inconsistent
with all other models we have used.
First, in the VI curve, the falling edge "maximum" is between the
"typical" and "minimum" curves.
Second, dV/dt_r and dV/dt_f do not increase from minimimum to typical to
maximum.
In both cases when firing these drivers into test loads (PCI-X), they do
not follow the expected trend where the "maximum" settings show the
fastest rise/fall time and the "minimum" settings show the slowest
rise/fall times.
This operations seems very odd, but given my limited experience with
dissecting IBIS models I'm open to suggestions on why this component
behaves the way it does.
Thanks,
Chris
> -----Original Message-----
> From: Ingraham, Andrew [mailto:a.ingraham@xxxxxxxx]=20
> Sent: Monday, November 17, 2003 9:38 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: IBIS Model error
>=20
>=20
> Suresh,
>=20
> All these errors point to an incorrect IBIS model. Contact=20
> IDT and ask them to fix it.
>=20
> The IBIS checker in the simulator tries to verify that the=20
> waveform data is consistent with the I-V tables. Ohm's law=20
> and the I-V tables should tell you the steady-state (initial=20
> and final) voltages, which ought to closely match those in=20
> the waveform tables. In this model, they do not come close.
>=20
> The I-V data doesn't seem to be pulling the output down. =20
> Even when driving a 50 ohm load resistor to 1.5V, the LOW=20
> state is 2.13V. Something is seriously wrong here.
>=20
> Regards,
> Andy
>=20
>=20
> ...
> > ERROR- Model IOPAD2546Z: The [Rising Waveform]
> > with [R_fixture]=3D50 Ohms and [V_fixture]=3D1.5V
> > has TYP column DC endpoints of 0.50V and 2.21v, but
> > an equivalent load applied to the model's I-V tables yields=20
> different=20
> > voltages ( 2.13V and 2.69V), a difference of 288.80% and 84.70%,=20
> > respectively.
> ...
>=20
>=20
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>=20
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