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ADS9224R: Registers confusion (reading, writing)

Nandan Dayal
Prodigy 30 points
Part Number: ADS9224R

1) If I send a command to SDI that says I want to read a register (e.g BUS_WIDTH register), where would I see the output of that register, I wasn't able to find this info on the datasheet (not sure if I missed it)? 

2) Every single register that is listed on the datasheet has reserved bits which specify that we should not write to them. How should we not write to them, since we are using the SDI to write in the bits, we will have to input a value somehow to SDI?

3) Let's say if we write to the PROTOCOL_CFG register, and activate the SPI-xy-S-SDR protocol. The SDO-0 to SDO-8 pins will be outputting whatever the ADC converts. If we were to send a command to SDI at that time saying I want to read a register, what would happen?

  • 0
    TI__Guru 64716 points

    Hello Nandan,

    Welcome to our forum and thank you for your post!

    1. After sending a register READ command, the contents of the register are output in the next frame.
    2. All RESERVED bit fields should be treated as NOP ("no-operation") bits. You can write 0b for these bits without any issue.
    3. I'm a little unsure of what you mean in this last question. The default SPI protocol is the SPI-00-S-SDR. Data will be clocked out of the device while you send the READ command. In the next frame, the conversion data will be replaced by the register contents.

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 30 points

    Hello Ryan,

    Thanks for responding.

    1) I remember reading this in the datasheet, but was confused what it meant "in the next frame". What pins exactly will the contents of the register be on? Does next frame mean SDO-0 - SDO-7?

    2) Got it!

    3) Okay that makes sense. Also, I think I mistakenly said the data would be out on SDO-0 to SDO-7, instead of SDO-0A and B. So, instead of the conversion data, the register contents will appear, and then the conversion data will appear again once all the register contents have appeared?

  • 0 in reply to Nandan Dayal
    TI__Guru 64716 points

    Hello Nandan,

    The register contents should be output on the same SDO pins that you've configured the device to use for conversion data. I'm confirming with my team whether this means both SDO_xA and SDO_xB will output the same thing or not. For example, if you're using the SDO-00-S-SDR interface, I believe you will see register contents in the next frame on SDO_0A and maybe also SDO_0B. Please give me a couple days to get back to you on this.

    Best regards,

  • 0 in reply to Ryan Andrews
    TI__Guru 64716 points

    Hello Nandan,

    The register contents will be output on both SDO_xA and SDO_xB.

    Regards,