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Original question:

SN75DPHY440SS: DA0P Lane not Passing HS Data

SN75DPHY440SS: 40% of DPHY440 units lost one pack of HS data after LP communication on Lane 0

Jerry Chen
Expert 5110 points
Part Number: SN75DPHY440SS

Hi team,

My customer found, after LP communication, 40% of the units lost one pack of HS data then recover to normal HS transmission. I didn't find similar issue on e2e. Could you pls give advice that where I could have a check?

Thanks.

  • 0
    TI__Guru**** 175971 points

    Hi,

    Is this a DSI or a CSI application?

    The DPHY440 lane 0 is a special lane. It supports DSI LP Backchannel. So, theDPHY440’s LP TX will expect to connect to an unterminated LP RX. With Lane 0 path (DA0P/N and DB0P/N) supporting bi-directional LP signaling, it is very important that DB0P/N LP TX is connected to an unterminated LP RX. If DB0P/N LP TX is connected to an HS RX, then LP signaling will not be able to reach the LP11 levels and which will cause the DPHY440 to not enable HS data path on Lane0.

    Can they enable HS path for Lane 0 only and see if they still lose HS packet?


    Write Register 0x50 with 8’h01 //Override enable for HS TX path
    Write Register 0x51 with 8’h01 //HS TX path enabled.
    Write Register 0x61 with 8’h00 // Disable LP path.
    Write Register 0x70 with 8’h01 //Override enable for HS RX path
    Write Register 0x71 with 8’h01 // HS RX path enabled.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 5110 points

    Hi David,

    Enabling HS path for Lane 0 only doesn't lose HS packet. In fact, it only lose one packet when about 4.3ms after LP communication. By the way, customer also found LP communication terminated after hardware reset DPHY440.

  • 0 in reply to Jerry Chen
    TI__Guru**** 175971 points

    Hi,

    I don't fully understand your response. If lane 0 is enabled for HS only, the source will only need to send HD packet only.

    The DPHY440’s LP TX will expect to connect to an unterminated LP RX. what do you mean LP communication terminated after hardware reset DPHY440?

    Thanks

    David