I don't see anything confusing here. If you want the EDA tool to shift the
waveform, you must tell the tool explicitly how much to shift.
Neither do I see anything cumbersome for model maker. Returning the DC_Offset
value in AMI_Init is just one line of code.
From: ibis-macro-bounce@xxxxxxxxxxxxx <ibis-macro-bounce@xxxxxxxxxxxxx> On
Behalf Of Fangyi Rao
Sent: Tuesday, August 13, 2019 6:06 PM
To: ambrishv@xxxxxxxxxxx; IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: DC_Offset BIRD - shifting the output waveform.
[EXTERNAL]
"and not shift the waveform and expect/let the EDA tool handle the shift."
Specifying the DC_Offset usage to be In is equivalent to telling the EDA tool
NOT to shift the waveform because the default output value of DC_Offset is 0.
If you want the EDA tool to shift the waveform, specify the DC_Offset usage to
be InOut and return the value in AMI_Init so that the EDA tool knows how much
to shift.
Fangyi
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
<ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>> On
Behalf Of Ambrish Varma
Sent: Tuesday, August 13, 2019 4:41 PM
To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>>
Subject: [ibis-macro] DC_Offset BIRD - shifting the output waveform.
[EXTERNAL]
Hi All,
At the end of today's meeting, I raised a couple of question about finding out
1. Who creates the final waveform - the EDA tool or the AMI Model and
2. Whether the waveform output from the Rx AMI Getwave is the physical
waveform at the latch.
It appeared that the lines in the Definition
"The output value of DC_Offset returned by Rx AMI_Init is to be added to the Rx
AMI_GetWave output waveform by EDA tools to form the complete waveform at the
Rx algorithmic model output."
clarified this. A few people in the meeting agreed that the EDA tool is the one
that creates the final waveform and that the Getwave output is NOT the waveform
at the latch.
On closer reading though - there is a scenario where I am still not clear if
that is the case.
If the DC_Offset is In, the BIRD says that the output value is assumed to be
0.0 Volt, in that case, the EDA tool is not creating the final waveform and the
waveform output is the output of the latch.
If the AMI model does not want to shift the O/P waveform, it has to pass the
DC_Offset value as an Out parameter such that the EDA tool may then create the
physical waveform.
This is a very common scenario where the AMI model may use the DC_Offset to
determine its CTE code/taps etc and not shift the waveform and expect/let the
EDA tool handle the shift.
In this case - it must pass the DC_Offset as an Out parameter which will be
cumbersome for the model/model maker.
This is confusing and will invite errors and result in faulty models.
Comments?
Thanks,
Ambrish.
