John,
There is a subtlety here. There is nothing in IBIS that prevents using AMI
modeling in memory channels, but the intent of AMI modeling was for
differential SerDes modeling. So do not expect all tools to support this
capability. The other part of this is how to process the results.
Generally tools assume the clock is imbedded in the data. DDR4 (DDR5?)
is(?) different. Generally DDR4 has eye mask rules at either the pin or
pad of the receiver, with AMI modeling one would need to specify rules at
the latch of the device. These rules are not defined as part of the model,
but the standard that the model is being used in. This is why I asked what
standards group (presumably JEDEC) is going to govern this capability.
Walter
From: Yan, John [mailto:jyan@xxxxxxxxxx]
Sent: Monday, January 25, 2016 2:59 PM
To: Walter Katz <wkatz@xxxxxxxxxx>
Cc: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
Subject: RE: There are no changes to the IBIS Parser to support AMI models
in single ended buffers
Hi Walter,
Thanks for following up.
This is good to know. If a customer finds a problem with the simulation
result, I can tell them that they should talk to their EDA supplier :)
I'll say the same thing when they try to simulate an IBIS-AMI model with
an IBIS model and when they try to simulate multi-drop configurations
since technically the channel is up to the EDA supplier.
Best Regards,
John
From: Walter Katz [ <mailto:wkatz@xxxxxxxxxx> mailto:wkatz@xxxxxxxxxx]
Sent: Monday, January 25, 2016 11:45 AM
To: Yan, John
Cc: IBIS-ATM
Subject: There are no changes to the IBIS Parser to support AMI models in
single ended buffers
John,
I verified that the IBIS 6.0 parser generate no warnings or errors when an
[Algorithmic Section] (interface to IBIS AMI model) is added to a singled
ended Input, Output or I/O buffer.
On page 171 IBIS 6.1 says:
"The [Algorithmic Model] always processes a single waveform regardless
whether the model is single-ended or differential. When the model is
differential, the waveform passed to the [Algorithmic Model] must be a
difference waveform."
The bottom line is that this is nothing in the IBIS specification that
limits AMI modeling to Inputs, Outputs, I/O, single ended or differential.
There is also no constraint in IBIS that the Impulse Response must start
at zero, and end at zero. A number of tools will generate an impulse
response by differentiating a step response. This will lose any DC offset
in the data, but this is a limitation of the implementation of AMI on that
tool.
IBIS does say that AMI modeling is used for SerDes designs, but does not
limit it as such. It certainly would not hurt to add some language that
AMI modeling can be used for other than SerDes.
Walter
Walter Katz
<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
