Re: [802.3ae] Proposed modifications to CJPAT
Tom Lindsay wrote:
> Folks - Per John D'Ambrosia's work on EMI and crosstalk testing for XAUI, it was recommended that
> CJPAT be modified to avoid transmitting synchronous patterns in all 4 lanes. I present 2 options
> for resolving this below.
I have to oppose this recommendation. One of the fundamental advantages
of the XAUI bus is that it has low EMI (due to the coding scheme). The
notion of developing a test to generate more EMI appears to contradict
this premise.
Secondly, the jitter test patterns were developed to allow testing of XAUI
modules in isolation from the system environment. Tests which over-
exercise the crosstalk and EMI would test the motherboard trace routing
more than the XAUI module in isolation. In other words, a great module
on a poorly routed board would be detected as a failing module - resulting
in finger pointing.
Thirdly, the generation of CJPAT requires fairly complex logic. The requirement
to generate four "correctly aligned" patterns un-necessarily complicates the
logic - requiring more gates and more power.
Lastly, the deadline for technical changes has passed.
The CJPAT was originally created to induce failure modes in the receiver
CDR. To that end, the pattern is good. The amount of effort required to
generate this new pattern is more than the failures it will induce.
--
Tim Warland P. Eng.
Applications Engineer
Quake Technologies (613)270-8113 ext 2311
Success is a journey, not a destination