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Hi David, During OFF state the PSE may select the impedance value. It can’t be too high since it needs to discharge Cpd in reasonable time so PD will be ready for next detection. During detection, the resistance must be >=45K and lower than some practical value. The PSE has very limited flexibility here. You said that
“There is no guaranteed 0.5mA offset”. During detection it is guaranteed. Not sure why you say this. Please clarify. Regards Yair From: Abramson, David [mailto:david.abramson@xxxxxx] EXTERNAL EMAIL Yair, There is no guaranteed 0.5mA offset. It is completely in the control of the PSE. The PSE can choose to have a lower Irev or no Irev at all. -Dave Sent from my phone. Please excuse the brevity. -------- Original message -------- From: Yair Darshan <YDarshan@xxxxxxxxxxxxx>
Date: 5/18/18 8:08 PM (GMT-05:00) Subject: [EXTERNAL] Re: [802.3_4PPOE] Classification Margin Slides- Review of David Abramson presentation by Yair
Hi Lennart, Thanks, please see below. Yair From: Lennart Yseboodt [mailto:lennart.yseboodt@xxxxxxxxxxx]
EXTERNAL EMAIL Hi Yair, First, nobody has suggested to allow Irev=1.3mA during classification, because this doesn't work. So we can discard that. Yair: Yes I know, we are now in
“0.5mA”. I was responding to earlier baseline number. Let's take Class 0 and Class 1 as an example. From the PSE's viewpoint it SHALL: - current of 0 to 5mA == Class 0 - current of 5 to 8 mA == Class 0 or Class 1 - current of 8 to 13mA == Class 1 The PSE has 3mA of grey area in which it can put the Class 0 / Class 1 threshold. Yair: Correct, and I want to concentrate on the case that the PSE threshold is set on one of the edges i.e. 5 or 8 mA.
The PD on the other hand has class current bands that are more narrow: Class 0 is 1 to 4 mA Class 1 is 9 to 12 mA Yair: Correct. By allowing Irev=0.5mA, we are essentially saying that now for the PD holds: Class 0 is 1 to 4.5 mA Class 1 is 9 to 12.5 mA Yair: Yes I know and I said in my response to David A presentation that it is not the problem that I am addressing. What changes for the PSE ? NOTHING. It still needs to - current of 0 to 5mA == Class 0 - current of 5 to 8 mA == Class 0 or Class 1 - current of 8 to 13mA == Class 1 Yair: My main concern is: there are PDs in the market that deviates from the PD requirements by up to 1mA e.g. 0.5mA since they utilize the (5-4)=1mA gape. So PDs that was used to be OK with legacy PSEs will not be with Type 3 and 4 PSEs due to the guaranteed addional “0.5mA”. This issue worry me it is kind of interoperability issue although you can argue it by saying
that the PD is not compliant.. there are millions of such PDs that where OK with Type 1 and 2 PSEs allowed margins. Now the margin will be short by 0.5mA.
There is no impact on PSE classification current margin. Kind regards, Lennart On Thu, 2018-05-17 at 08:09 +0000, Yair Darshan wrote:
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