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I am not literate in the uses/implications/etc. of the state
diagrams, and recognize that.

That said, I don't see a PSE denying or removing power
from a PD as necessarily a "Fault" in the sense of failure,
particularly as a PD may be dealing with more potential
power demand from devices than the PSE has the capacity for.
As an imperfect analogy, this seems to me like a vending
machine that could be broken (so a fault) and not able to
deliver candy bars -- or one that is simply out of the kind
you want (so also unable to deliver, but not a fault in the
sense of equipment failure).

Whether this should change how the state diagrams are
constructed or labeled, I can't say.  Thanks,


On Wed, Feb 11, 2015 at 10:39 AM, Dan Dove <dan.dove@xxxxxxxxxxxxxxxxxx> wrote:
Hi All,

In my work related to cleaning up the PSE state diagram as initiated at our last meeting, a drawing was put together by Dave Dwelley as a first stab of how one might break down the PSE diagram.

In this, (attached), the state "POWER_DENIED" was included in the "Delivering Power" group. As I proceeded on my task, I noted that POWER_DENIED could be considered a "Fault" condition depending on how you read the text.

I looked at the text and found the following; Power Denied or Removed (12.12)
When read as a one, bit 12.12 indicates that power has been denied or has been removed due to a fault
condition. This bit shall be set to one when the PSE state diagram (Figure 33–9) enters the states
‘POWER_DENIED’ or ‘ERROR_DELAY.’ The Power Denied bit shall be implemented with latching high
behavior as defined in 33.5.1.

So it occurs to me that the text is somewhat ambiguous. If you read it "{has been denied or has been removed} due to a fault condition"... you read the condition as a fault for either. If you read it "has been denied or {has been removed due to a fault condition}, then denial is not considered a fault, but removal due to a fault condition is a fault.

So, in order to move forward, I am going to consider the former for the basis of my effort. I will presume that denial of power is a "self-imposed fault" to advance this effort. If, due to consideration of the Task Force, its decided that this state should not be within the Fault group, it will be relatively easy to redraw things.

Feedback appreciated. In the last meeting, we discussed using the reflector for this purpose, hence, I'm reflecting on this issue.

Dan Dove
Chief Consultant
Dove Networking Solutions
530-906-3683 - Mobile

Bruce Nordman
Lawrence Berkeley National Laboratory
m: 510-501-7943