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ADS131M08: ADS131m08 vs. ADS131a04

Todd Anderson3
Intellectual 370 points
Part Number: ADS131M08
Other Parts Discussed in Thread: ADS1018, , ADS131A04,

There appears to be a lot of differences between these two parts, and because I am using both in the product, I need some clarification.

The a04 has a RREGS command, the m08 has RREG command that does the same thing? Why are the opcodes different?

Not quite sure how to do a single register read/write on m08 - does it have similar single frame mechanism as a04?

Are there always 10-frame mechanisms on m08? If i want to initialize registers, do I use only 10-frame mechanisms?

Why are the EVMs so different from each other? Could there not be a single platform (microcontroller-based) with multiple EVM boards?

(For instance, the ADS1018 EVM can also be directly connected to a Launchpad board - very nice!)

I will be receiving the ADS131m08EVM shortly - hopefully, a lot of questions will be answered by observation of the SPI bus, but until then I am perplexed.

Regards,

Todd Anderson

  • 0
    TI__Guru 66186 points

    Hi Todd,

    We try to make the interface protocol similar in most cases, but the ADS131A04 was designed a bit differently. The ADS131A04 allows you to read the register contents from the COMMAND STATUS RESPONSE words only, without causing you to miss data. Therefore, if you read more than one register, it will take multiple frames to read the register contents, as shown in Figure 76. For a single register read, the response of the next frame immediately contains the register contents (Figure 75).

    On the ADS131M08, you will use the same command for both single and multiple register reads. The op-code is a fixed two-byte op-code, which contains the starting address and the number of registers to read minus one. If you are reading only one register (nnn nnnn = 0h), then the register contents are contained in the response word of the next frame, followed by channel conversion data (Figure 8-23). For multiple registers, the response contains an acknowledgement of the command, followed by the register contents of each register requested in place of the channel data. The frame must be extended to accommodate all of the register data (Figure 8-24).

    To write multiple registers on the ADS131M08, you simply need to extend the frame to accommodate the total number of registers written.

    I completely understand your point about the EVM platforms. This has been a goal of our team for quite some time. The ADS131A04 was developed back when we were a smaller product line and supported only delta-sigma ADCs. Now we support SAR, delta-sigma, audio codecs, and isolated modulators and amplifiers! Believe it or not, we are closer than ever to standardizing our EVMs to only a few platforms (subject to change... Wink)

    In the meantime, we'll do our best to support your questions as quickly as we can.

    Best regards,

    Ryan