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DAC53204: readback mode adds a 1 to the read register, for R/W ?

THOMAS WALTER
Prodigy 170 points
Part Number: DAC53204


Tool/software:

Hi,

I am using the echo (readback ?) mode of the DAC53204, but in the echo frame it is like if the first bit (MSB) was set to 1 altough sent  0 (write command).

Here, I send write on 0x26 and it echoes 0xA6 which is 0x26 with MSB to 1:

I wasn't expecting this, I was expecting a deformation less echo.

Is it normal ?

  • 0
    TI__Expert 4970 points

    Hi,

    The device should be echoing the previous command, with a write command to 0x26, it should echo that same command back.

    I have a few clarifying questions about the scenario:

    Was the write command successful?

    Was this the first command after power up for the device? Or did you communicate with the device before the picture?

    Are you able to zoom into the SPI so we can observe if the data bits are lining up properly with the SCLK?

    Thanks,
    Lucas

  • 0 in reply to Lucas Burnette
    Prodigy 170 points

    Hi, well noted.

    To answer your questions:

    - The command was indeed successfull, as it is the one enabling the echo (SPI 26h: interface config: SDO EN).

    - It is the first command after power up.

    For what its worth here is a zoom

    I will check if the problem persist with other than the first frame

  • 0 in reply to THOMAS WALTER
    Prodigy 170 points

    Hi,

    To better answer your question I made a loop write so we can exclude the first frame.

    Here are the results:

    I send:

    0x26 0x00 0x01 --> Echoes 0xA6 0x00 0x01

    0x1F 0x12 0x49 --> Echoes 0x9F 0x12 0x49

    0xFF 0x0F 0xF0 --> Echoes 0xC0 0x00 0x00 (normal as invalid address) ?

    As you can see, for the 2 valid addresses, the MSB of the echo is always set to 1.

    Analog domain seems also OK

  • +1 in reply to THOMAS WALTER
    TI__Mastermind 42273 points

    Hi Thomas, 

    The MSB is always set to 1 in the echo like you have observed. I've asked the design team about this before, and they have verified that this is inherent to the SDO design. 

    Best,

    Katlynne Jone