[ibis-serdes-backchan] AMI Modeling, an introduction specifically targeted to time domain analysis.
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: <ibis-serdes-backchan@xxxxxxxxxxxxx>
- Date: Wed, 9 Feb 2011 14:58:47 -0500
All,
In my last e-mail, I described how IBIS AMI models are used to do
statistical analysis. IBIS AMI models are also capable of doing time domain
analysis as well. The same sequence of calls to the AMI_Init functions are
still required. The AMI_Init functions not only generate the data for doing
statistical analysis, they also are used to initialize the DLL to prepare it
for time domain analysis using the AMI_GetWave function. In the current
supported flow, after the Tx AMI_Init and Rx AMI_Init functions are called,
the Tx AMI_GetWave and Rx AMI_GetWave functions are called iteratively.
To be specific, a long stimulus waveform is created in short sections
(~1000UI). The stimulus is a "digital" stimulus with the time of the
transitions including various Jitter impairments such as DCD, Rj, Sj, . The
output of Tx AMI_GetWave is a waveform that includes the algorithmic part of
the Tx equalization. This waveform is normally convolved with the Impulse
Response of the channel to get the waveform that is then input the Rx
AMI_GetWave. The output of the Rx AMI_GetWave call is the waveform at the
decision point of the Rx buffer, along with a list of clock ticks. The EDA
tool processes the waveform and clock ticks on the fly to generate an eye
and a clock PDF.
Simulations of e6 UI and even 100e6 UI are not uncommon. The waveform is
partitioned into small (~1000UI) sections since allocated waveforms 100e6 UI
(with 32 samples per UI) would become unwieldy.
As the EDA Tool alternates between calls to the Tx and Rx AMI_GetWave. The
Rx AMI_GetWave can, based on the quality of the waveform at the Rx decision
point, determine not only improved Rx tap and peaking filter setting, but
can direct the Tx AMI_GetWave function to modify its tap coefficients. This
is the basic mechanism for supporting time domain backchannel
co-optimization. The Rx AMI_GetWave function can model at any level of
detail the method that the RX Silicon actually makes decisions and
recommendations to the Tx AMI_GetWave. This method relies on the Tx and Rx
AMI_GetWave being called on small chunks of the waveform. There are lots of
details to be worked out, like how to communicate to the EDA tool on each
call to Rx AMI_GetWave the data pattern that has to be fed into Tx
AMI_GetWave, and what commands the Rx AMI_GetWave needs to communicate to
the Tx AMI_GetWave.
Walter
Walter Katz
Chief Scientist
Signal Integrity Software, Inc.
wkatz@xxxxxxxxxx
303.449-2308
Other related posts:
- » [ibis-serdes-backchan] AMI Modeling, an introduction specifically targeted to time domain analysis. - Walter Katz
