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Re: XAUI Driver Spec


The receiver max amplitude need to be higher than transmitter to allow
margin and protection.  Very likely in Tampa the max transmit amplitude
be raised, where 1.6 V max will become more logical.  The 1.6 volts is
diff. so each wire only drives 800 mV.




Robbie Shergill wrote:
> Hello all,
> Last week in Austin the XAUI group decided to change Max Diff. Amplitude to
> 1.6 volts. As I understood it, the rationale for increasing the max amplitude
> was to achieve commonality with the Infiniband spec. Although I agree with
> the spirit of this rationale, I checked the Infiniband spec and found
> that they are trying to drive a cable as well as a backplane with one
> electrical specification; thus the reason for the 1.6v spec. In this
> case, I'm not sure if it is worth matching the Infiniband spec in this
> one area. My feeling is that a driver circuit can be made to drive
> up to either 1.0 volt or 1.6 volt relatively easily; but it would be
> much more troublesome for a (XAUI) receiver to tolerate 1.6 volts
> *needlessley*.
> So, if the above reasoning is agreed to by others, I would propose that we
> stay with 1.0 volt max. diff. amplitude that is in the current draft 1.0
> (page 119, line 22).
> -Robbie Shergill
>  National Semiconductor