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Original question:

TPS23881: False Detection and classification in semi auto mode even when POE power is OFF

TPS23881: PSE Controller Detection Event for 4-pair Auto-class configured ports when connected to 2-pair PD

Jerry Leung
Prodigy 20 points
Part Number: TPS23881

Tool/software:

Hi,

I want to verify whether or not this is an expected behavior when I configure the TPS23881 as an auto-class 4-pair port, and connected to a 2-pair PD (Type 2).  I see the PD load powered up successfully but I continue to see the the Detection Event Register (0x05h CoR) indicating a detection cycle occurred when I poll status on the I2C bus.  Is this due to the fact that the other pair is left unconnected?

Thanks for the help in advance,

Jerry

  • 0
    TI__Prodigy 595 points

    Hi Jerry, 

    Thanks for your question. What is the value you are reading for 0x05? Which channels of the device are being used with the 2-pair PD? 

    In the meantime, I will test this on our end and get back to you. 

    Best,

    Anagha

  • 0 in reply to Anagha Jagannath
    Prodigy 20 points

    Thank you for investigating, attaching an image below for reference.  I'm reading out the (0x05h) register that clears on read.  When I first enable the channel I see the detection at 8 (0b1000), which corresponds to DETC4, then goes to value 4 for DETC3 (0b0100). 

    Interesting though is that I thought on the cycle where the value read out 8, I thought it would be 12 (0b1100), corresponding to a detection cycle on both DETC4 and DETC3.


  • 0 in reply to Jerry Leung
    TI__Prodigy 595 points

    Hi Jerry, 

    Thanks for providing register reads. Unfortunately, I was unable to recreate this issue. I had a follow up question - are all 4 pair-sets connected to the diode bridge on the PD?

    Below are the steps in our test procedure: 

    1. Power on 881 EVM

    2. Enable Autoclass on all channels (0x50)

    3. Connect to PD (one diode bridge has been removed, ensuring that PD is only 2-pair)

    4. Read Detection Event Register (0x05) - reading is always 0F, meaning that detection has occurred on DETC1, DETC2, DETC3, and DETC4. 

    Can you please provide your test setup? 

    Best,

    Anagha

  • 0 in reply to Anagha Jagannath
    Prodigy 20 points

    Interesting... I think this is similar to what I'm seeing.  In my setup I don't have the first port connected and not enabled so I don't expect DETC1 and DETC2 to go through a detection cycle and flag. 

    On the PD side I just have 2 pairs connected to the diode bridge with the other 2 pairs unused and unconnected.


    When I connect to a 4-pair PD I see the Read Detection Event register (0x05) flag in one cycle but then once it's powered up the register is cleared and does not keep indicating it's going through detection.