Hot!short connection interruptions at KSZ9896

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mcumaker
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2018/09/19 00:31:38 (permalink)
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short connection interruptions at KSZ9896

Hello,
I use the switch KSZ9896. My devices consist of a switch and a CortexM3-MCU connected via RMII/IIC. All devices hang in a daisy chain and receive mainly unicast UDP packets (traffic about 100kByte/device). Loops and time delays are no problems. I also entered the entries from the document "Silicon Errata" (it's a pity that almost all entries in the datasheet are undocumented and not traceable).
It works quite satisfactorily with two test setups of 20 and 10 devices.

Now to the problem: In irregular intervals (between 2min and 2h) the link seems to disappear at random places of the chain. I monitor the link state via the "PHY Basic Status Register" and/or the "PHY Digital PMA/PCS Status Register" of the KSZ9896. With the first one I also pay attention to the "Latch Low" function and read twice. If the link status changes for more than one second, my devices send a status message.
The disconnections are mostly short (probably about one second for auto-negotation) but still visible. Sometimes the connection stays away completely.

My questions:
- Is the behavior known or has it occurred in a similar way before somewhere?
- If so, how can the connection breaks be eliminated?
- or is there a way to find out what caused the connection to fail?




#1

2 Replies Related Threads

    ufficiotecnico@ailux.eu
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    Re: Link interruptions at KSZ9896 port 2018/09/25 00:32:20 (permalink)
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    Hi
    We have the same problem. The KSZ9896 is connectect to a NXP MCF52252 via MII 100Mbps (Port 6).
    A port (Port 2) is connected to a UDOO card that has the physical layer at 1000Mbps (Micrel KSZ9031rnxca).
    The other 4 ports are programmed as HUB / Switch 10/100Mbps. The link, on Port 2 disappears after a period of time that varies
    from a few minutes to a few hours and does not return until after the power on.
    The UDOO card connected to any other external device (PC, Switch etc.) works correctly without interruption.
    The other 4 ports connected to any other external device operate correctly without interruption.
    Now, why we must force the speed to 100MBps to have link to the UDOO Card?
    Why after few time this port lose link?
    We are very worried because we have to go into production with the cards and we have no alternative
    since we need 5 physical layer ports and we maybe can not change chip (maybe the KSZ9897 have the same issue).
    We hope that someone have an answer to help us...
    #2
    mcumaker
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    Re: Link interruptions at KSZ9896 port 2018/10/29 00:35:08 (permalink)
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    My problem is fixed:
    the switch was configured wrong.

    The registers are big-endianess but our I2C routines wrote little-endianess (MMD 16Bit Register Set). As a result, the workaround for the silicon errata was not really active.
    In my case, interruptions came from the non-functioning EEE (as described in the error data sheet).

    Now everything is running very well and error free.


    #3
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