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ADS112C04: Repeated START condition

Hiroaki Yuyama TED
Expert 1840 points

Part Number: ADS112C04

Dear, support team.
I have a question about ADS112C04.

About Sr (Repeated START condition)
Looking at the RDATA command in the data sheet, the RDATA command section and the SLAVE ADDRESS section that follows are separated by Sr (Repeated START condition).


Is it possible to divide this Sr part by STOP and START and divide it into two transactions as shown in the figure below?

The I2C master may not support Sr, and I would like to check if Sr support is required.

Best Regards,
Hiroaki Yuyama

  • 0
    TI__Guru** 113765 points

    Hi Yuyama-san,

    I am not aware of any microcontrollers that cannot send a repeated start as this is part of the I2C specification.  Using the repeated start is the fastest way to retrieve the data from the ADS112C04. 

    As to your specific question, sending the communication as 2 communication frames should be doable according to the design specification document of the ADS112C04.  Writing the RDATA command will load the output buffer with conversion data that can be then read out of the ADS112C04 in the next frame with a read.

    However, you cannot mix commands.  For example, if you write the RDATA command and then in the next frame write the RREG command, you will no longer be able to retrieve the conversion data until another RDATA command has been written to the ADS112C04.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Expert 1840 points

    Hi Bob-san,
    Thank you for your answer.

    I understand the I2C frame.
    When I send the RDATA command, I want to read the data in the next frame.

    Best regards,
    Hiroaki Yuyama 
    Tokyo Electron Device Analog FAE

  • 0 in reply to Hiroaki Yuyama TED
    TI__Guru** 113765 points

    Hi Yuyama-san,

    Sending the write frame for the RDATA command followed by the read frame is acceptable.

    Best regards,

    Bob B 

  • 0 in reply to Bob Benjamin
    Expert 1840 points

    Hi Bob-san,
    Thank you for your reply

    I understand that it is permissible to send a read frame following the write frame of the RDATA command.
    We will tell our customer engineers that we can send the I2C frame in two parts.

    Best regards,
    Hiroaki Yuyama