Re: [IBIS-Users] IBIS AMI analog channel

From: Todd Westerhoff <twesterh_at_.....>
Date: Wed Sep 23 2009 - 05:31:04 PDT

Eric,

The way I usually describe this is to say the impulse response "contains the effects of the transmitter's analog back end, channel and the receiver's input termination network".  There are a number of ways to derive this, but one way is to take the network consisting of the transmitter analog output, channel model and the receiver input and simulate the step response.  The waveform at the receiver pad is then differentiated to obtain the impulse response for the analog network.

The "high impedance" points on slide 3 are shown to illustrate why the link can be broken into analog and algorithmic sections in the first place; i.e. why the two step process of network characterization and channel simulation is valid.

Does that help?

Todd.

Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@sisoft.com
www.sisoft.com

Eric Monteiro wrote:

Hello

 

Upon reviewing the following presentation:

http://www.eda.org/ibis/summits/jul09/katz1.pdf pages 3 through 6

 

Where the impulse respone is measured remains unlear. 

 

1) I assume the ideal pulse is forced at the input of the Tx and the output is measured after the analog front end of the Rx (i.e. the input to the CDR).

 

So my question is, where have other model developers forced the impulse (input or output of Tx), and measured the impulse reponse (input or output of Rx) that is then passed to AMI_Init?

 

2) If the pulse is indeed forced at the input of the Tx, and meausred at the output of the Rx (right before the CDR) does that not mean that AMI is NOT compatible with current IBIS models since you can't measure an output from an Rx input buffer?  In which case, AMI should just be its own standalone standard not imbeded within an IBIS model (like ICM), shouldn't it?

 

Regards,

Eric

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