I2C read from AD5593R registers all return same value

I have seen this same question posted here and elsewhere, but see no subsequent resolution posted.

In my system I2C transactions to the part get ACK'd, and appear ok to me on a scope … but every address I read returns 0x0FF3.

As an example, below is scope shot of I2C transaction that attempts to read from the NOP control register, which I would expect to return 0x0000.

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  • So ... answered my own question.  For anyone else whom makes this same mistake:

    Missed in datasheet that their is an explicit "register readback" mode value of the pointer byte.   This means to read back a control register written to by a pointer byte value of 0x0X you have to perform a read of I2C data address 0x7X ... not 0x0X as I obviously guessed. 

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  • So ... answered my own question.  For anyone else whom makes this same mistake:

    Missed in datasheet that their is an explicit "register readback" mode value of the pointer byte.   This means to read back a control register written to by a pointer byte value of 0x0X you have to perform a read of I2C data address 0x7X ... not 0x0X as I obviously guessed. 

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