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TUSB8042A: Downstream ports reset after connecting/disconnecting upstream port

Part Number: TUSB8042A
Other Parts Discussed in Thread: TUSB8042

Hi, 

I am using TUSB8042 and I am configuring it using SMBUS. I have everything working and I have configured downstream ports with BATEn. I observed that when I connect/disconnect upstream port, downstream ports reset. I understand that the downstream port have different modes when upstream port is connected/disconnected. I was wondering if there is a way I can avoid resetting of downstream ports. 

Thank you. 

  • Hi Kunal,

    If battery charging is supported, the downstream ports must reset between normal active mode and charging only mode.  This is because in charging only mode, the device has completed the charging mode only handshake (DCP mode) and will not connect to the hub until it is reset.  Likewise, a reset is necessary to get the downstream devices to exit normal mode and do the charging mode only handshake.  It is possible to implement a hub without using power switches, but not if you are also implementing battery charging.

    Regards,

    JMMN