comments on Clause 47
All,
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 47.3.3.5 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.
Regards,
Mike
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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 http://www.lsilogic.com |_____|
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