• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 45 subscribers
  • Views 467 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS124S06: ADS124S06 RDATA continuous SCLK after all bytes were read

Masa Katayama
Intellectual 970 points
Part Number: ADS124S06
Other Parts Discussed in Thread: ADS1248

Dear Sir,

I have a question about RDATA command of the section 9.5.4.2 of d/s.

About DOUT/DRDY data if SCLK is continuing after all bytes were read which is after CRC were read on Figure 91 of d/s. 

The d/s describes that DOUT/DRDY will repeat to output from STATUS, Data1 . . . . again and again, is it correct understanding?

And what data will be read if SCLK is continuing after the following ADC conversion was completed? Is it still old data before conversion and need another RDATA to get new converted data (by monitoring /DRDY, referring Figure 86), or DOUT_DRDY will send new converted data without RDATA command again?

If both using /DRDY or every RDATA command for reading consecutive conversion data work, what is advantage/dis-advantage each? 

ADS1248 has RDATAC, so I am not sure how or if ADS124S06 will do similar.  

Best regards,

Masa

   

  • 0
    TI__Guru** 113765 points

    Hi Masa,

    Both the ADS1248 and the ADS124S06 have a command to read the conversion results (RDATA) and also have a direct read method.  For the ADS1248, the direct method is accomplished by first issuing the RDATAC (read data continuously) mode where data is then placed into the output shift register and can be read by issuing the correct number of SCLKs.  The ADS124S06 differs in two ways.  The first is there is no RDATAC command and the new conversion result is always placed into the output buffer after the conversion completes.  The second difference is the result can be read a second (or more times) by reissuing the SCLKs.  You can think of the output data buffer in this case as a ring or cyclical buffer.  The ADS1248 does not do this.

    When using the read data direct, the contents of the buffer must be read soon after DRDY transitions from high to low and the entire result must be read before the next conversion result completes and updates the output buffer otherwise the data will become corrupt.  So the ADS124S06 will work the same as the ADS1248 in RDATAC mode in this respect. 

    If the timing of DRDY is an issue with the ability to read the result, then it is best to use the RDATA command.  The data will go into the cyclical output buffer and is valid until all data are transmitted the first time.  However, I will have to check with the designer to see if continuing to send SCLKs after the first time can have the data corrupted if a new conversion completes while reading the result.  I believe it is possible to have corrupted data similar to the read data direct method if the data is read more than one time out of the output buffer.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    TI__Guru** 113765 points
    Hi Masa,

    I did check with the designer and my statements were correct in my previous post. Even though the conversion result can be read many times after the RDATA command is issued, the result is only truly valid the first time it is read. If additional SCLKs are sent to reread the contents of the buffer, the buffer can be updated and the result being read corrupted if a DRDY update should occur while reading the buffer contents. If the timing of the system is uncertain and DRDY is not monitored, then the RDATA command should be issued each time the conversion result is read.

    Best regards,
    Bob B