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comments on Clause 47


I have two comments on the XAUI driver electrical specs in clause 47.
Ballot comments will be submitted, but I want to air them here on the
reflector in case I'm missing some piece of history on these issues.

1) Section 47.3.3  Driver characteristics:  (Table 47-1)
	Present maximum driver voltage is 2.3 volts.  I'm unaware
	of the origin of this number, but it seems to pointlessly(?)
	exclude devices with higher supply voltages.  I propose 
	this spec be changed to 3.3 volts.

	Also the minimum driver voltage is listed as -0.3 volts.
	I propose that this value be changed to -0.4 volts.  The
	motivation is to not preclude any driver that swings
	around ground.  The max dif'l swing of 1600 mVp-p implies
	a max single-ended zero-peak voltage of 400 mV, which
	would be the max swing below ground.

2) Section Driver template:  (Table 47-3)
	Present values for X1 and X2 are 0.325 and 0.450 UI,
	respectively.  I understand these are typos and comments
	have likely been submitted.  I propose (as I assume other
	comments will) that X1 be 0.175 UI, half the peak-peak TX
	jitter spec.  Several values have been proposed for X2,
	including X1+0.19 UI (the Fibre Channel value), as well as 
	a larger value.  I propose X2 = X1+0.205 UI = 0.380 UI.
	The derivation for this is attached, and is the closest
	I can come to the original Fibre Channel methodology.
	(The difference between X2=X1+0.19 and X2=X1+0.205 is
	about 5 ps, so this is not much of a big deal either way.)

Thanks in advance to anyone who can provide (helpful) feedback.

 Mike Jenkins               Phone: 408.433.7901            _____     
 LSI Logic Corp, ms/G715      Fax: 408.433.7461        LSI|LOGIC| (R)   
 1525 McCarthy Blvd.       mailto:Jenkins@xxxxxxxx        |     |     
 Milpitas, CA  95035      |_____|