[ibis-macro] Re: redriver in spice simulation

  • From: Todd Westerhoff <twesterh@xxxxxxxxxx>
  • To: ambrishv@xxxxxxxxxxx
  • Date: Tue, 12 Mar 2013 21:23:41 -0400 (EDT)


I guess I missed part of this conversation. What problem are you trying to 


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Todd Westerhoff 
VP, Software Products 
Signal Integrity Software Inc. • www.sisoft.com 
6 Clock Tower Place • Suite 250 • Maynard, MA 01754 
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“ I want to live like that” 
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----- Original Message -----

From: "Ambrish Varma" <ambrishv@xxxxxxxxxxx> 
To: "fangyi rao" <fangyi_rao@xxxxxxxxxxx>, ibis-macro@xxxxxxxxxxxxx 
Sent: Tuesday, March 12, 2013 7:34:02 PM 
Subject: [ibis-macro] Re: redriver in spice simulation 

Actually, if we short the Rx and Tx of the redriver, regular spice simulations 
using IBIS models and analog repeaters will have issues with the Tx trying to 
pullup to power and pulldown to ground. 

In that case, redriver simulation within the realm of an IBIS cct, solutions 
can be: 

1) No spice (non AMI) simulation allowed for redrivers (easier) 
2) Series switch like implementation (harder) 


From: fangyi_rao@xxxxxxxxxxx [mailto:fangyi_rao@xxxxxxxxxxx] 
Sent: Tuesday, March 12, 2013 4:58 PM 
To: Ambrish Varma; ibis-macro@xxxxxxxxxxxxx 
Subject: redriver in spice simulation 

Hi, Ambrish; 

I am not sure if your suggestion of shorting redriver Rx ibis output pin to the 
redriver Tx ibis input pin in spice simulations will work because in spice 

1. legacy Tx ibis model is driven by input signal threshold crossing events. 
That’s not how a redriver Tx half is driven by input signal. 
2. legacy Rx ibis model output is a digital signal of 1’s and 0’s (hopefully I 
am correct here). That’s not what redriver Rx half outputs. 

Due to the uncertainties in redriver model behavior in non-AMI simulations, I 
prefer to keep my redriver BIRD separate from Walter’s repeater BIRD, at least 
for now. 


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