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Re: [802.3ae] XGMII output load requirements

The XGMII compatible output driver should be an HSTL Class I compatible driver
with the additional requirement of having an output impedance greater than 38
ohm. It should be designed to drive a 50 ohm unterminated line. The 38 ohm
limit ensures acceptable signal quality.
The output driver must meet the timing specification while driving the test


"Grow, Bob" wrote:

> You are working from an old draft.  The current draft is D4.2.  I will leave
> interpretation of the draft to you, since a draft is subject to change.  I
> don't recall in which previous draft the language around the 10 pF changed,
> but I vaguely recall it changing at some point, and it now is used only in
> the context of conformance testing.
> Bob Grow
> Chair, IEEE 802.3
> (Editor, 802.3ae clause 46)
> -----Original Message-----
> From: Iliana Fujimori [mailto:iliana.fujimori@xxxxxxxxxx]
> Sent: Monday, March 25, 2002 9:30 AM
> To: stds-802-3-hssg@xxxxxxxx
> Cc: Iliana Fujimori
> Subject: [802.3ae] XGMII output load requirements
> Dear Editor,
> I am wondering about the output load requirements for the XGMII output
> buffers.  According to IEEE Draft P802.3ae/D3.1 section 46.4, an output
> impedance greater than 38 ohms is required along with a capacitive load
> of 10 pF.  These two figures give me a time constant of  380 ps.  Could
> you please let me know if this is the correct interpretation of the
> specification?
> Thank you for your attention.
> Sincerely,
> Iliana Fujimori
> Design Engineer
> Silicon Laboratories
> (603)891-3650 x 17
> iliana.fujimori@xxxxxxxxxx