[ibis-macro] input to Tx analog model
- From: <fangyi_rao@xxxxxxxxxxx>
- To: <ibis-macro@xxxxxxxxxxxxx>
- Date: Wed, 19 Jan 2011 20:10:49 -0700
Hi, Experts,
In light of IBIS analog model enhancement discussed at recent ATM meetings, I
want to raise a question: in SPICE level transient simulations (w/o AMI), what
is the input signal to the Tx analog model?
In IBIS 5.0 the answer is simple. The input is digital signal whose threshold
crossing events trigger rise and fall edges being formed and transmitted. The
swing and waveform of the edges are part of the analog model. They are
independent of the input signal and user doesn't need to know about them.
If we are to make Tx analog model able to accept AMI_GetWave output waveform as
input, we need to abandon this notion of event trigger and make the input
signal a continuous analog waveform (e.g. PWL). The output waveform of Tx
analog model will be directly shaped by the input waveform. As a result, to run
a SPICE level transient simulation (w/o AMI) user has to look up the swing and
slope parameters (Voh, Vol, trise, etc) from model files in order to create the
input signal with proper amplitude and shape.
Is this an acceptable use model for transient? If user replace his old model
with a new one, then the result is most likely wrong because his old digital
input signal doesn't have the correct amplitude and slope.
Regards,
Fangyi
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