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ADS131B04-Q1: SPI commands and responses

Todd Anderson3
Intellectual 370 points
Part Number: ADS131B04-Q1
Other Parts Discussed in Thread: ADS131A04, , ADS131A02

All:

From reading the datasheet, it appears that any spi command issued to the device results in 6 frames in reply, regardless of whether it is a single command. True?

(So in that respect, it differs from the ADS131A04?)

Regards,

Todd Anderson

  • 0
    TI__Mastermind 23785 points

    Hi Todd,

    I tried to explain how many words are output in an SPI  frame in section '8.5.1.6 SPI Communication Frames' in the ADS131B04-Q1 datasheet.
    The number of words for a RREG and WREG command can be different than six depending on how many register you want to read or write respectively.
    For all other commands the frame size is always 6 words as you correctly stated - even when you disable any of the ADC channels.

    Regards,

  • 0 in reply to Joachim Wuerker
    Intellectual 370 points

    Joachim:

    By the way - excellent part! This is a great addition to the ADS131 family.

    I am looking at Figure 8-14, which shows a single command with CRC, but the DOUT has 6 frames of response. I am also looking at Figure 53 of SBAS590E - ADS131A02, ADS131A04 which shows "Fixed verses Dynamic-Frame Modes in Standby Mode". I recommend that Figure 8-14 be modified to look like the d) Dynamic Frame Size (CRC Enabled).

    It looks like the SPI behavior of ADS131B04 is no different than the ADS131A04, correct?

    Regards,

    Todd Anderson

  • 0 in reply to Todd Anderson3
    TI__Mastermind 23785 points

    Hi Todd,

    thanks a lot for the positive feedback! It is always great and encouraging to hear that from our customers.

    The ADS131B04-Q1 doesn't really offer this 'dynamic frame size mode'.
    The output CRC for example cannot be disabled. It is always output by the device, but the host can simply ignore it or the host could 'short-cycle' the frame under certain conditions as explained in section '8.5.1.8 Short SPI Frames'.
    Also the device always outputs the data words for all 4 ADCs even when one or more ADCs are disabled or if the device is in standby mode.

    The only time the frame size could change is when reading or writing register data as shown in the RREG and WREG sections of the datasheet.
    I would agree though that the datasheet could benefit from some more timing diagrams for various scenarios. Let's see what I can come up with for the next datasheet revision.

    Regards,