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DAC128S085: Daisy-chain operation

Lach Temelkov
Prodigy 110 points
Part Number: DAC128S085

We have 2 DACS hooked in a daisy-chain operation. As such, user has to always write to  both DACs    SPI_MOSI: <DAC2><DAC1>

If a channel on DAC1 need be updated but no channel on DAC2 needs updating, is there a NOP( No Operation) command for DAC2 ( I don't see it)?

Could you describe the right sequence for writing daisy chained DACs for the example above?

  • +1
    TI__Mastermind 28008 points

    Hi Lach,

    I do not know of a NOP command for this device. There are 4 command bits and it looks like every combination of those bits associated with a command.

    It should be safe to send the highlighted command with DB[11:0] set to 0. This way none of the DAC registers will be updated.

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 110 points

    Hi Katlynne,

    Thanks for the response. I have been using the highlighted command above, but I am using a persistent storage array in the following way:

    If i need to update DAC1 and not DAC 2, I read the old value from my array storage for DAC2 ( the value DAC2 channel was set last). 

    In that way, DAC1 is updated with new value and DAC1 is updated with the same old value - that is just workaround.

    It never occurred to me that 1010 command can be send with empty D[11:0] . That would work

    Thanks

  • +1 in reply to Lach Temelkov
    TI__Mastermind 28008 points

    Hi Lach,

    I do not have a  DAC128S085 on hand to test this with so please reach out if this ends up not working for some reason and we can brainstorm another solution. 

    If it does work for you, then great! Feel free to reach out if you have any additional questions. 

    Best,

    Katlynne Jones