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ADS1263: Serial Interface Chip Select Signal

Rico Schmitt73
Prodigy 100 points
Part Number: ADS1263

Hello,

I am wondering about the Chip Select Signal for a transmission longer than 2 bytes. This is from the Datasheet at page 87.

To produce this kind of communication it is nessasary to drive the CS signal by the application software instead of the SSI module (SSI Module of the TM4C only operates with maximum 16bits message length)

I am not sure about Note 1. So i was wondering if the following communcation Signal would work. If this is the case i could use the DMA Operations.

My intetion here is to send 4 1-byte messages using the CS signal in the SSI Module. This would look like:

Thanks for your help :)

  • 0
    TI__Mastermind 44680 points

    Hi Rico,

    The ADS1263 interface is "SPI-compatible" but it does not fully adhere to the Motorola SPI standard and this is one of the main differences...

    The /CS pin on the ADS1263 frames the data bytes and toggling it between command bytes will terminate the command. The reasons for this are:

    1. The ADC data and commands are variable length.
    2. The synchronization of the the master and slave can be "reset" and corrected (by toggling /CS) should a glitch occur on SCLK.
    3. Multiples devices on the same SPI bus will require some kind of manual selection using GPIOs anyways.

    Generally, you can configure the SSI frame signal pin to be a GPIO output and manually control it inside of the functions that send SPI commands.

    Regarding Note 1 in Figure 122...When /CS is tied low there is no way of "resetting" the SPI communication, unless you use the SPI timeout feature of the ADS1263. Therefore, the ADS1263 will expect you to finish sending all of the command bytes. Sending a partial command and then starting a new command will result in the both SPI commands being decoded incorrectly.

    Best regards,
    Chris