[ibis-macro] Re: ignore_bits and TX vs. RX

  • From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
  • To: "michael.mirmak@xxxxxxxxx" <michael.mirmak@xxxxxxxxx>, "IBIS-ATM (ibis-macro@xxxxxxxxxxxxx)" <ibis-macro@xxxxxxxxxxxxx>
  • Date: Wed, 27 Jun 2012 13:43:44 -0700

I would say that the tool would need to ignore only 35 bits in the waveform for 
deducing the final results. My understanding is that the tool does not really 
'shorten' the number of bits by the ignore bits, but actually simply 'ignores' 
it in the final analysis for results etc, as that is the number of bits 
required for the models to adapt/optimize or settle down.



Ambrish Varma   |  Member of Consulting Staff

P: 978.262.6431   www.cadence.com<http://www.cadence.com>

From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Mirmak, Michael
Sent: Wednesday, June 27, 2012 4:31 PM
To: IBIS-ATM (ibis-macro@xxxxxxxxxxxxx)
Subject: [ibis-macro] ignore_bits and TX vs. RX

A deceptively simple question...

Ignore_bits as a parameter can apply to the TX or the RX.  The language of the 
specification states that it determines the number of bits to be ignored by the 
simulation tool.

In the case where I have a link where only an isolated TX or an isolated RX, 
this is easy to understand.  But what happens when I combine a TX with an RX on 
the same link where both use ignore_bits?

I would assume that the TX (using GetWave) would provide the tool with a 
waveform that the tool would then shorten by the stated number of bits (say, 
21.  But would the RX GetWave then use the shortened waveform in its own 
analysis, before the tool reports back an even shorter waveform?

Specifically, if ignore_bits is 21 in the TX, and ignore_bits is 35 in the RX, 
does that mean that the final waveform reported out by the tool would be 
shorter than the original pattern by 56 bits?

-          MM

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