Hi Chad,
This is totally different case.
In clause 33 we add a text “Transients less than 30 μs in duration may cause the voltage at the PI to fall below VTran-2P.” that was not appeared in clause 33.
The addition of it creates a valid question i.e. what to do with this piece of information?
I am asking to explicitly say what to do with it. To say “No requirements are specified for transients <30usec” is also clear statement which makes it similar to clause 33.
We can’t be worse than clause 33 in terms of clarity.
That is why I disagree with your statement “If we listed everything that wasn’t specified, we’d never finish” since I am not asking to specify new requirement. I am asking to clarify what was clear in clause 33 and now in clause 145 it is not.
Yair
EXTERNAL EMAIL
Yair, we’ve be at this specification stuff for 15 years (you and I). Many, many times we have talked about how we don’t address what’s not addressed (and yes, that circular text was intentional). If we listed everything that wasn’t specified, we’d never finish. I cannot support the addition of this statement.
Chad Jones
Tech Lead, Cisco Systems
Chair, IEEE P802.3bt 4PPoE Task Force
Principal, NFPA 70 CMP3
After seeing all the responses, I propose the following remedy to my comment below.
The concept is to make it similar to what we have in clause 33 which is no PSE requirements for transients below 30usec
Make the following changes:
"Transients less than 30 μs in duration may cause the voltage at the PI to fall below VTran-2P. Requirements for Transients less than 30 μs in duration are not specified. See 145.3.8.6 for PD transient requirements."
Other option is to delete “"Transients less than 30 μs in duration may cause the voltage at the PI to fall below VTran-2P.” however I see the value with keeping this text but to complete explicitly the needed requirements which is in this case “no requirements are specified”.
Yair
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In clause 145 in the PD side we have clear requirements for what to do below 30usec and what to do between 30-250usec.
In the PSE side, it is only clear what to do between 30usec to 250usec.
Below 30usec the spec just giving us the info that the voltage can be lower than Vtran-2P but doesn’t say what to do in this case.
If for example we didn’t have this text "Transients less than 30 μs in duration may cause the voltage at the PI to fall below VTran-2P” as we don’t have in clause 33, that it will not be raising the question OK so what netx? What is the requirement from PSE in that case. Should we keep the power? Should we remove power? We don’t care? Or It is system decision? (i.e. may or may not remove power or “no requirements are specified” ? This is the problem that I am trying to resolve.
Yair
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