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TUSB8020B: Issues with documentation for configuration file

Part Number: TUSB8020B

I'm working on a configuration file to program an EEPROM and am running into some confusing information in the spec sheet.

In particular there are three areas for each offset that seem to relate to a "default" or reset value.

1) line with the name of the register, the line ends with a [reset = xxxx]

2) line under the yellow line, shows values for each bit

3) in the table the column labeled Reset

Sometimes all three have the same data, sometimes they are different. The documentation never says what each of these three are supposed to be so it is a little tough to figure out what to put in the configuration file.

One in particular is the offset 05, the device configuration register. Bit 1 says it is R/W so I need to put something in the file, but the description just says to use the default, but the three fields above disagree as to what the default it. So I don't know what to put in the file.

Offset 09 the PHY configuration register, says everything is reserved, but some bits are R/W, and again the three fields are different, what should I put in this offset?

The next is about custom strings. The documentation says to use UTF-16LE, my understanding of this is that each character takes two bytes, so the length field should be twice the number of characters. The LE encoding of  an upper case "A" would have the 41h in the lower byte offset and 00h in the upper byte offset. Is this correct?

Thanks,

John S.

  • Hi John,

    Bit 1 in register 5 should be 0, the X value is just intended to indicate that the values of bit 3 and bit 4 can be dependent on the associated pin configurations.

    All of register 9 should be 0, that is definitely a typo in the second line of Figure 12.

    Yes, the UTF-16LE encoding requires two bytes for each character. My notes show that the byte order is swapped, so "A" would be "41 00" in the EEPROM file.

    Regards,
    JMMN
  • Hi John,

    Please post if you have any more questions, otherwise I will close this thread.

    Thanks!
    JMMN
  • This works, just one issue, the strings for manufacture and product are seen and displayed on Macs but not on Windows (at least win8 and win10, haven't tried on win7 yet). Its exactly the same programmed board, but shows up differently on different OSes.

    Windows must be looking at something different that was not changed. We have gone through every parameter in the detail list and none have changed. We made sure we know which one is the TUSB8020B.

    It would be nice if our windows customers could see the strings, but it is not a show stopper.

    Thanks,

    John S.
  • John,

    The TUSB8020B reports the same descriptors regardless of host. If you want to check the reported descriptors on Windows machines, you can load usbview.exe (it is a debug application available for free from Microsoft). Install the utility, select the hub in the left hand window, select the Options > Config Descriptor, and then Options -> Auto refresh and then hit F5. You should be able to see most descriptors reported by the hub in the right hand window. There will be two instances for the hub (one for USB 2.0 and one for USB 3.0).

    Regards,
    JMMN