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DAC61416: DAC61416 Streaming Mode Interaction with SDO Enable

Jemiah Aitch
Prodigy 10 points
Part Number: DAC61416

I'm using the DAC61416RHAT and configuring it VIA SPI.  3.3V system voltage,  3.3V SPI voltage using a clock of 2MHz.

I'm observing an issue where, when the STR-EN bit is set in the SPICONFIG register, the SDO pin becomes disabled as though the SDO-EN has been cleared. I experimented with some of the other bits in same register and isolated it to that specific bit. In the attached scope trace, you can see that Register writes of 0x0AA4 (the default value) and 0x0A84 leave the SDO pin operational. Writing a value of 0x0A8C (with STR-EN set) cause the SDO pin to go dead. The datasheet doesn't appear to show any relation between Streaming Mode and SDO output. Please see the attached scope trace. It shows each value being written twice to demonstrate the status of the SDO pin. First 0x0AA4, then 0x0A84, then 0x0A8C.  The last value adds in the STR-EN bit while keeping SDO-EN high and the SDO pin goes dead (Idle-High)


I'd appreciate any insights.

Thanks

.

  • 0
    TI__Mastermind 34098 points

    Hi Jemiah, 

    Sanjay is reviewing and will get back to you soon.

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    TI__Expert 3600 points

    Hi Jemiah, 

     

    SDO enable works only in normal and daisy-chain mode and SDO is disabled in Streaming mode as daisy-chain and streaming modes are not compatible with respect to the data interpretation.
     

    Thanks,

    Sanjay 

  • 0 in reply to Sanjay
    Prodigy 10 points

    Thanks Sanjay. 

    I was able to verify that the chip was still listening, even if it wasn't answering. I saw the bit in the datasheet about the daisy-chain limitation. It just said that it wasn't supported in Streaming mode, not that the SDO pin would be fully disabled.  It's unfortunate that it's not possible to verify register settings while in Streaming Mode. It would be nice if the data sheet was more explicit about that. The good news is that the part (along with the system it's in) is working perfectly. It's good to have this little mystery solved though. Thank you for that. 

    Jemiah

    .

  • 0 in reply to Jemiah Aitch
    TI__Expert 3600 points

    Hi Jemiah, 

     

    I understand your pain point and we will rectify this in next revision of the data sheet and make it more clear. 
     

    Thanks,

    Sanjay