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TUSB8020B: Clarification on SMBUS "Unsupported Protocol"

Michael Balourdas
Expert 4745 points
Part Number: TUSB8020B

Hello,

I'd like just to get some clarity the following section of the datasheet. My interpretation is that while the device is in SMBus mode set by the SMBusz pin, no other protocol can access the device (including standard I2C). Otherwise, in I2C mode, the device can be connected to a standard I2C host and communicate. Might be obvious, but I want to be sure.

Thanks,

Michael

  • 0
    TI__Guru 60865 points

    Hi Michael,

    In SMBUS mode, the hub is configured to be accessed by a SMBUS host and will not connect as a hub until the SMBUS host has set the cfgactive bit in the hub registers.  In this mode the hub is the target of the SMBUS (I2C) host.

    In I2C mode, the hub is configured to access an external I2C EEPROM.  If it does not find an EEPROM attached, it will use the pin configurations to configure the hub. In this mode the hub is the host of the I2C target.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 4745 points

    Hi JMMN,

    So if the device is in I2C mode, it can be used with a standard I2C host and does not need to support the SMBus protocol, correct?

    Thanks,

    Michael

  • 0 in reply to Michael Balourdas
    TI__Guru 60865 points

    Hi Michael,

    No, if the hub is in I2C mode - it is the I2C host.  If the hub is in SMBUS mode, it can be accessed by a host.  Please note that SMBUS and I2C are very similar, so if you have a I2C host it should be able to access the hub in SMBUS mode.

    Regards,

    JMMN