Subject: rise & fall waveforms

From: Tim McKinney <[email-masked]>
Date: Wed, 23 Jul 1997 10:46:03 CDT

My question is about rising and falling waveforms.
In order to generate these curves with s2ibis2, you have to specify
certain parameters for the test fixture.  This makes it relevent to
that specific fixture.  So, should these curves be generated
only when making actual measurements to produce an IBIS model,
or should I generate them using s2ibis2 ?
If I should generate them with the automatic conversion,
what is a common fixture resistance?

Tim Mcinney
[email-masked]

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From: Andy Ingraham <[email-masked]>
Date: Wed, 23 Jul 97 22:26:46 EDT

> or should I generate them using s2ibis2 ?

They are meaningful whether generated by SPICE or measured data.  
Test fixture = test load (applied to the SPICE model, or to the
real DUT via test fixtures.)

> what is a common fixture resistance?

For ordinary TTL/CMOS outputs, try 50 or 100 ohms to GND (for rising)
and to POWER (for falling).  Also a few other resistances, up to
1000 ohms or so.  Do the same when you generate measured data.

Regards,
Andy