[SI-LIST] Re: Test Loading Issues on Quad XTK

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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