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[ DS90UB925 & UB928 ] Register Settings

Kenichiro
Mastermind 9165 points


Hi,
Can you help me to answer for queries on FPD-Link III from my customer?
<DS90UB925, "PCLK Auto" setting and output status>:
I would like to make sure how device behave under loss of PCLK condition.
When "PCLK Auto" is set to 1(default), device still can maintain its video transmission and back channel communication, correcct?
On the other hand, if "PCLK Auto" is set to 0, no communication can be achieved.
Here I summarized in the table.
<DS90UB928, Forward Channel Sequence Error bit>:
Can you check whether register type of "Forward Channel Sequence Error" bit is correct?
If it's same as UB926, this should be "R".
<DS90UB928, GPIO0, normal operation>:
Can you let me know what is the "normal operation" of GPIO0 pin?
GPIO0 Function Enable bit enable to select GPIO0 mode between "normal mode(default)" and "GPIO operation".
However, GPIO0 pin should be single function pin and no other function is employed on this pin.
Thanks,
Ken
  • 0
    TI__Genius 14015 points

    Hi Ken,

    1) Your table is close. On the 925, if PCLK auto is set to 1 and PCLK is lost, then there will only be back channel communication. This means back channel in both forward and backward directions, but not video transmission. You can still access registers remotely via I2C when PCLK is lost. If PCLK auto is set to 0, lock will be lost and communication severed when PCLK is lost. 

    2) The forward channel sequence error bit is indeed Read-Only, as on the 926. The datasheet has an error.

    3) This description is a holdover from the 925/926 datasheets, which have GPIO's that share pins with video data pins. In that case, 'normal operation' would be video transmission. In the 927/928 case, GPIO EN set to 0 just disables the GPIO. 

    Let me know if you have any more questions!

    Thanks,
    Jason 

  • 0 in reply to Jason Blackman
    Mastermind 9165 points
    Hi Jason,
     
    Thank you for your support!!
    I think now I can discuss with customer, so I will come back to you, if necessary.
     
    Wrt datasheet typo, it's really appreciated, if you give this feedback to your document team.
     
    Thanks,
    Ken