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TUSB8020B: Two questions

Shu-Cheng LIN
Guru 11785 points
Part Number: TUSB8020B
Other Parts Discussed in Thread: TUSB8041

Hi Sirs,

Sorry to bother you.

1. If TUSB8020 two I2C/SMBUS to be high (3.3v) it mean external I/F, right? so if no data on I2C EEPRON, no setting from SMBUS host side.

Does TUSB8020B still can be enable?

2. As below, if no data on EEPRON, the 8020 will still into programming mode? if yes, what is program data?

Thanks!!

  • 0
    Guru 11785 points
    Hi Sirs,
    Sorry for pushed, have any update on this case?
    Thanks!!
  • 0 in reply to Shu-Cheng LIN
    TI__Guru**** 181321 points
    Shu-Cheng

    Sorry for the delay.

    1. The hub will still be powered up, but TUSB8020B will not enumerate until the SMBus host configures the device and/or clearing the CFG_ACTIVE bit.

    2. When the hub enters programming mode, it reports a different VID/PID than the usual hub VID/PID to the host controller so that a programming endpoint driver can be loaded. While in programming mode, the TUSB8041 does not operate as a hub: only the upstream USB port is active.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 11785 points

    Hi Sirs,

    Thanks for your reply.

    Actually we have meet same issue on 8041 before. HUB upstream couldn't active until removed I2C/SMBUS Pull high resistor 

    We still not clear why Hub need into programming mode?? because I2C pull up, the hub is be host to read EEPROM, find EEPROM no data then into programming mode?

    In this time only upstream USB port is active? down stream no function?

  • 0 in reply to Shu-Cheng LIN
    TI__Guru**** 181321 points
    Shu-Cheng

    There are two reasons for the hub to remain in programming mode:

    SMBUSz is asserted and the SMBUS host has not set/cleared the cfg active bit
    An unprogrammed EEPROM is attached

    So the hub will go into programming mode if the EEPROM is not programmed. And when hub is in programming mode, only upstream USB port is active.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 11785 points

    Hi David,

    Thanks for your reply.

    We still not clear why Hub need into programming mode.

    Based on before information, no data on EEPROM or no SMBUS comment to HUB, the HUB will into programming mode. right?

    Then there will different VID/PID report to Host? Upstream port can successful connected but down stream doesn't work? why need this limitation?

    By the way, when no data on EEPROM or no SMBUS comment, why HUB couldn't switch internal OTP?

  • 0 in reply to Shu-Cheng LIN
    TI__Guru 60870 points
    Hi Shu-Cheng,

    The TUSB8041 will automatically enter USB programming mode if:

    SMBUSz is pulled low, this is to prevent the hub from connecting to USB before the SMBUS host has the time to configure the hub.

    SMBUSz is pulled high, and a blank EEPROM is connected to the SDA and SCL lines, this is to enable quicker EEPROM programming during production.

    The hub should not enter programming mode if SMBUSz is pulled high and no EEPROM is attached.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Guru 11785 points
    Hi Sirs,
    Thanks for your reply. Actually we use TUSB8020B, so it's same as TUSB8041, right?
  • 0 in reply to Shu-Cheng LIN
    TI__Guru 60870 points
    Yes, the behavior is the same for TUSB8041 and TUSB8020B. Sorry for the confusion.

    Regards,
    JMMN