FreeLists / si-list / [SI-LIST] Re: Double Rising Waveform and Falling Waveform in one IBIS model

["Beal, Weston" <weston_beal@xxxxxxxxxxx>]

 Heinrich,

This IBIS specification doesn't define how the simulator should handle
these waveforms. The simulator programmer has to figure out a good way
to do it. I think all the simulators that use the rising and falling
waveforms do essentially the same thing, though. Given two rising or
falling waveforms, the simulator calculates internal time-dependent
current multipliers using linear equations. Think of the two waveforms
as two points in a plane and draw a line between them. This line is
analogous to the internal time-dependent current multiplier. If there is
only one waveform it is like one point in the plane and the desired line
is not defined. In fact, if the IBIS model has only one rising or one
falling waveform, the simulator probably has to assume something logical
for the other waveform in order to solve the linear equation.

In reality, the equation is not linear, but a 1st order differential
equation because of the C_comp parameter. Additionally, the inclusion of
the C_dut, L_dut, C_fixture, and L_fixture parameters turns the internal
calculation into a 5th order differential equation which potentially
introduces more error in the digital solution. I recommend NOT including
these reactive elements if possible.

Regards,
Weston


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Heinrich.Smith
Sent: Thursday, March 03, 2005 1:07 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Double Rising Waveform and Falling Waveform in one
IBIS model

Hi, all

  In some IBIS model, you may notice that some have two rising waveform
sections and two falling waveform sections with different test fixtures
in one model. And I wonder how the model works with these double rising
waveforms and double waveforms at the same time while the simulation
goes on. If anybody get ideas about this, please tell me the story. I'll
be really very appreciated!!
  Thx
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