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I have a question about the PSE Interface, Detection and Safety!
In the actual IEEE 802.3af standard, 33.2.9 Power supply allocation, the behaviour of connecting a PSE PI with another PSE PI is not explained.
33.2.9 Power supply allocation
A PSE shall not initiate power provision to a link if the PSE is unable to provide the maximum power level
requested by the PD based on the PD’s class. Where a PSE does not provide the optional classification function
specified in 33.2.7, all PDs are treated as Class 0.
The PSE may manage the allocation of power based on additional information beyond the classification of
the attached PD. Allocating power based on additional information about the attached PD, and the mechanism
for obtaining that additional information, is beyond the scope of this standard with the exception that
the allocation of power shall not be based solely on the historical data of the power consumption of the
If the system implements a power allocation algorithm, no additional behavioral requirement is placed on
the system as it approaches or reaches its maximum power subscription. Specifically, the interaction
between one PSE PI and another PSE PI in the same system is beyond the scope of this standard.
In the industrial field, line and ring topologies are very common, so my question is:
Does the new IEEE 802.3at standard explain this issue?
What happens if I connect two PSE PI’s together?
Can anybody help me with this question?
With best regards, mit freundlichen Grüssen
Hirschmann Automation and Control GmbH
Ê +49 7127 14-1561
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] Im Auftrag von McCormack, Michael
I would like to update everyone on the schedule for our work.
We are down to the end, please remain focused so we can complete.
Business Development Manager, Power over Ethernet
Hirschmann Automation and Control GmbH, Neckartenzlingen
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