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TUSB4020BI: I2C interface

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Replies: 3

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Part Number: TUSB4020BI

Hi,

Do we need to program the chip through I2C to get usb hub working? Or we can use directly the chip without any I2C/SPI programming.  

Please check the post linked with this for functional usage block diagram.

  • Hi Selvaraj,

    No, I2C is not needed for hub operation.  Please note that if a pulldown resistor is installed on SMBUSz, the hub will hang in programming mode until a SMBUS host configures it.  Also if SMBUSz is pulled high, the hub will hang in programming mode if a blank EEPROM is installed.  In all other case, the hub defaults to pin configuration mode.

    Regards,

    JMMN

  • In reply to JMMN:

    Hi JMMN,

    Thanks.

    As per the datasheet following is the definition of SMBUSz pin,

    "SMBUS mode.

    The value of the terminal is sampled at the deassertion of reset to enable

    I2C or SMBus mode.

    0 = SMBus mode selected

    1 = I2C mode selected

    After reset, this signal is driven low by the TUSB4020BI. Due to this behavior, it is recommended to not

    tie directly to supply but instead pull-up or pull-down using external resistor.".

    As per your above comments i need to leave this pin unconnected right?. Is my understanding correct?

    What is blank EPROM? Is it refers to TUSB4020'S internal ROM?.we have not connected any external EEPROM.

    Please share the details of default pin configuration mode you have mentioned in comments ?

  • In reply to Selvaraj Karuppusamy:

    The SMBUSz pin has an internal pull-up, it can be left unconnected for pin configuration mode.  EEPROM refers to an external I2C EEPROM.  See notes below:

    • if SMBUSz pin is pulled low, the hub will stay in programming mode until a SMBUS host configures it and clears the cfgactive bit.. 
    • if SMBUSz pin is pulled high, the hub will stay in programming mode if a blank EEPROM is installed. 
    • if SMBUSz pin is pulled high, the hub will read in configuration data if a programmed EEPROM is installed. 
    • if SMBUSz pin is pulled high, the hub will default to pin configuration mode if a no EEPROM is installed. 

    Pin configuration refers to using the FULLPWRMGMTz, GANGED, PWRCTL_POL and BATENx pin settings to configure the hub operation.

    Regards,

    JMMN