[10GBASE-CX4] Comments on latest revision
To the CX4 SG,
Congratulations on a great job of pulling all of this together. Thank you
for the opportunity to comment.
sections
54.6.7 and 54.6.8 Global and Lane-by-lane transmit disable functions.
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I think that the "Global" disable function should be mandatory and the
"Lane-by-lane" disable should be optional. Because this is CX4 and not
four asynchronous channels, the link should disabled with one bit. It
doesn't really matter if you have MDIO, one bit is as easy as four bits to
set. In designs without the optional MDIO, one bit becomes much easier to
implement than four. The priority should be placed on disabling the link
in as simple a manner as possible. One bit (a.k.a. one pin) does this.
"Lane-by-lane" disable is helpful for debugging and evaluating designs,
but it does not make sense at runtime for a XAUI link. Please make the
"Lane-by-lane" disable the option for those who need to tinker off line.
section
54.7.3.4 Amplitude and Swing (and Table 54-6)
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Line 37 - Dc-reference logic level is meaningless because of the ac
coupling. This makes sense.
Line 38 - If dc-reference logic level is meaningless because of the ac
coupling, then the common mode voltage should also be meaningless. A dc
common-mode voltage requirement does not make sense. I recommend deleting
the common-mode voltage requirement.
Regards,
Clark Foley
Maxim Integrated Products
(503) 547-2018