[SI-LIST] Re: ibis-ami models clarification.
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 28 Mar 2013 15:48:59 +0000
Balamanikandan,
Todd is correct that strictly speaking you have a non-IBIS
specification compliant IBIS-AMI model, because the spec
says that (pg. 122):
" The “analog” portion of the channel is characterized by means of an impulse
response leveraging the IBIS constructs for device models defined in Sections
6, 6A and 6B. "
However, if the EDA tool you are using has a simulator which
can handle other types of buffer models, such as transistor
level SPICE models, you can use those models in place of the
IBIS buffer models.
You have to realize that in an IBIS-AMI simulation the analog
buffer models are needed for running a channel characterization
simulation to generate the impulse response of the channel.
One way of doing this is to run a normal time domain step
response and take a derivative of that. Such step responses
can be simulated with .ibs models just as well as with SPICE
transistor models, or even other types of behavioral models,
such as Verilog-A or VHDL-AMS. (Our tools, by the way can
simulate with any of these models).
Once the impulse response is available, the EDA tool will read
the .ami parameter file, and pass the parameters and the impulse
response to the AMI DLL-s and executes them. Once the AMI DLLs
are done, the EDA toll will post process the results if necessary
and display it to the user.
The delay parameters you mention seem to be the parameters of the
[Driver Schedule] keyword in the .ibs file. You can make a normal
IBIS model with this keyword for a pre/de-emphasis buffer, which
is basically a two-tap SERDES buffer. You could use this model
instead of an AMI DLL to generate eye diagrams, but these are
still a lot slower than the AMI DLL-s, so you will not be able
to generate millions of bits worth of data for your eye diagram.
The main difference between a [Driver Schedule] model and AMI DLL
model is that the first is used in normal time-domain simulations.
The simulator is a nodal simulator which solves the currents and
voltages iteratively keeping all the laws (Ohm's, Kirchoff's, etc...)
IBIS-AMI models (DLL-s) contain signal processing algorithms, and
do not have to solve for voltages and currents iteratively. This
is why they are so much faster. Since these AMI DLL-s are binary
executables, they do not belong in the .ibs file.
I hope this answers most of your questions.
Thanks,
Arpad
======================================================================
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Todd Westerhoff
Sent: Thursday, March 28, 2013 5:20 AM
To: kbmanick@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ibis-ami models clarification.
Bala,
What you have been provided is not a compliant IBIS-AMI model.
AMI files use a different syntax than the .ibs file because they are one to one
associated with algorithmic models and serve a different purpose than the .ibs
file. We created a syntax that is better suited to describing the algorithmic
model, and it didn't make sense to include it in the .ibs file.
Todd.
--
Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx
www.sisoft.com
“I want to live like that"
-Sidewalk Prophets
On Mar 28, 2013, at 2:31 AM, Balamanikandan K <kbmanick@xxxxxxxxx> wrote:
> 1.
> IBIS-Ami Models consists of 3 portions all of which must be provided by the
> vendor.
>
> 1) Analog models for the transmitter and receiver (IBIS format)
>
> 2) Compiled Algorithmic models (the DLL library for Windows, or SO library
> for Linux/Unix)
>
> 3) A parameter file (.ami) for the algorithmic models
>
> But I have a file from a vendor. Name of the folder contains ibis-ami.
>
> But the folder contains spice files, AMI files and dll files. It does not
> contain a file with ibs extension.
>
> Is this an ibis-ami file? If spice file are available what is the purpose
> of ami file here? Please explain.
>
>
>
> 2. I know that AMI models define device parameters such as pre-emphasis and
> equalization that standard IBIS buffer models cannot.
>
> But, in an ibis model (not ibis-AMI model) Rise on delay, rise off delay,
> fall on delay, fall off delay are mentioned for the driver to handle pre
> emphasis.
>
> What way this ibis model differs from ibis-ami model?
>
> In ibis-ami model, Why are the ami models not integrated into the ibis
> file itself?
>
> Please clarify me and *refer me an application note to understand.*
>
>
> --
> Best Regards,
> Balamanikandan.K
>
>
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