[SI-LIST] Re: Test Loading Issues on Quad XTK
- From: "lting168" <Lawrence.Ting@xxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 29 Apr 2003 01:13:37 -0000
Thanks for your kindly help.
But, I don't understand if test loading parameters are not present in
the IBIS model and V(m) correction is enable in the XTK,
how XTK can still generate V(m) data.
Lawrence
--- In si-list@xxxxxxxxxxxxxxx, "Abe Riazi" <ariazi@xxxx> wrote:
>
> Dear Lawrence and others,
>
> In my opinion, when considering the effects of TIME_TO_VM in XTK
> simulations we need to focus on two operations:
>
> I. IBIS2XTK
> II. XNS
>
> How TIME_TO_VM comes into existence and influences results are
> explained below.
>
> I. When translating an IBIS model into QUAD format, IBIS2XTK
normally
> computes TIME_TO_VM (by calling the "mtest" program) if the timing
test =
> load=20
> parameters (e.g. Vmeas, Vref, Rref, Cref ) are present in the IBIS
=
> file.=20
>
> However, to ensure reliable TIME_TO_VM values in XTK models, it is
a =
> good=20
> practice to manually determine/check TIME_TO_VM values. This
usually =
> involves=20
> obtaining the test load parameters ( Vmeas, Vref, Rref, Cref )
either =
> from the=20
> IBIS model (or preferably from the device data sheet), carrying out
XNS =
> simulation
> and then measuring the rise and fall delays (by definition
TIME_TO_VM is =
> the time
> it takes the driver output to cross the Vmeas voltage when the
driver is =
> connected to a=20
> desired test load).=20
>
>
> II. With the V(m) correction Enabled, XNS will subtract the driver =
> TIME_TO_VM and
> report the corrected delays in .idd, .rep and .gen files. Such =
> TIME_TO_VM
> correction (to prevent double counting of buffer intrinsic delay)
can =
> prove critical when
> flight time values are to be applied for setup and hold margin =
> computations.
> Furthermore, the delays measured by the XNS (or TLC) cursors differ
from =
> the delays
> reported when TIME_TO_VM correction is enabled. However, as noted
by =
> Jon Powell
> TIME_TO_VM does not have any effects on signal quality such a
> overshoot/undershoot, ringback, etc.
>
> In summary, it is important that during the model =
> translation/verification phase,=20
> accurate TIME_TO_VM parameters be incorporated into the model's =
> DRIVERSPEC. This requires utilization of correct timing parameters
( =
> Vmeas, Vref, Rref, Cref )
> and measurement approach. During the XNS simulations, with the V
(m) =
> correction
> enabled the reported rise and fall delays (in .rep , .idd, and .gen
=
> files) differ from those
> which can be manually measured by the XNS (or TLC) cursors.
> =20
>
> Best Regards,
>
> Abe Riazi
> ServerWorks
>
> -----Original Message-----
> From: lting168 [SMTP:Lawrence.Ting@xxxx]
> Sent: Monday, April 28, 2003 3:30 AM
> To: si-list@xxxx
> Subject: [SI-LIST] Test Loading Issues on Quad XTK
>
>
> Dear all,
>
> I am using Quad XTK to do simulation. When I get the rising delay
or=20
> falling delay data, those values should be substrated by the=20
> Time_TO_VM values from the IBIS model of driver. However, if the
IBIS=20
> model doesn't include Time_TO_VM data, XTK automatically
generates=20
> the Time_to_VM values. Does anyone know how these values come from?
>
> Thanks in advance
>
> Lawrence
>
>
>
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