AnsweredAssumed Answered

Ethernet MII mode issue on i.MX8MM (Applied PHY IC : KSZ8081MNX)

Question asked by Lee Jaehee on Sep 3, 2019
Latest reply on Sep 10, 2019 by igorpadykov

Please see the attached file for detail Picture : Ethernet MII mode issue on i.MX8MM_wKSZ8081MNX_20190904.pptx

* Applied IC

    1) Applied CPU : i.MX8MM (MAC included, possible RGMII/MII)   
    2) Applied PHY IC : KSZ8081MNX (Only MII mode)


1. Symptom
    A) ping communication between [PHY]-[MAC] is impossible (MAC setting : MII mode)

   Picture A.1) : when connecting <TXC line> between [PHY]&[MAC] measuring <TXC line>

   Picture A.2) : when cutting <TXC line> between [PHY]&[MAC] and measuring <TXC line > of PHY side.

   Picture A.3) : when cutting <TXC line> between [PHY]&[MAC] and measuring <TXC line > of MAC side.

   >> 25MHz Clock comes out from PHY side, Clock does not come out from MAC,

        Voltage level decreases when connected to each other

 

 B) Ping communication between [PHY]&[MAC] is possible, but sometimes disconnection(MAC setting: RGMII)

  Picture B.1) when connecting <TXC line> between [PHY]&[MAC] measuring <TXC line>

    >> 25MHz clock comes outboth PHY & MAC

       So, Ping communication seems sometimes possible because the signal is overlapped,

       but there is a disconnection depending on the voltage level.


2. Review for RGMII vs MII

   1) RGMII : TXC(TxClock) go to from [MAC] to [PHY]

   2) MII : TXC(TxClock) go to from [PHY] to [MAC] > Our Case

 

3. Symptom prediction

    1) We suspect the setting forENET_TXC“ net(Ball no.: AG24) of i.MX8MM for MII modeseems to be wrong.


4. Request

    1) please sharea patch or SW guide for MII mode.

    2) please share the HW guide for MII mode.  

 

 

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