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ADS131M06: DRDY SYNC BETWEEN TWO DEVICES

srinath B
Prodigy 100 points
Part Number: ADS131M06
Other Parts Discussed in Thread: AMC131M03, ADS131M04,

Hi, i have attahced an image of DRDY signal of two devices ADS131M04 and AMC131M03, image.png

in this image blue and yellow waveforms are two DRDY signals from each device. 

blue colour : AMC131M03

yellow colour : ADS131M04 

pink: single SPI 

and both the devices are controlled through single SPI, sync and clkin signal. and you we can see the both the device are synced almost.

here my doubt is when blue waveform drdy is low spi transfer is happening and blue colour become high, meanwhile the yellow color drdy signal is becoming high after reading from that particular device only, till that yellow wave form is low.

so my doubt, when the DRDY signal will become actually high, after reading from the device or what,  till then it will be low or what.

because the yellow waveform is low only , after reading only it is becoming high.

 

and another doubt we planned to use two ads131m06 but for that CLKIN signal only same , rest of other signals like spi, sync/rst, cs are all different, so both the devices can be synced or not same like the above image.

 

regards,

srinath

  • 0
    TI__Mastermind 46915 points

    Hi srinath,

    For both ADS131M04 and AMC131M03, the /DRDY will switch from low to high when the ADCs are shifting out the last word (CRC). The falling edge of the /DRDY indicates that the data is ready so you only need to check the falling edge of the /DRDY signals by using /DRDY as an interrupt to your MCU. Both /DRDY in your timing have been aligned very well at the falling edges, so I did not see any issue from the timing you shared, both ADCs worked well.

    BR,

    Dale

  • 0 in reply to Dale Li
    Prodigy 100 points

    Hi Dale,

    Thanks, 

    my doubt is DRDY signal transition from low to high happens only ADC are shifting out last word, till then the DRDY will be low only? you can see the image above message yellow waveform, yellow waveform is low until reading from device and shifted to high after last word out.

    if we not read the data from device, that time DRDY low to high transition how will work? DRDY will be low only until next read happens.

    with 2 ADS131M06 how this sync will work, for that CLKIN only same, rest of other signal is different from MCU.

    regards,

    Srinath

  • 0 in reply to srinath B
    TI__Mastermind 46915 points

    Hi srinath,

    The behavior of /DRDY is more complicated than what you thought. If you did not read the data, the /DRDY can still go to high and then to low when next data is ready, but the pulse of /DRDY will become narrow to indicate that the data has been omitted. As I said, you only need to monitor the falling edge of /DRDY for reading data.

    Please see the 8.5.2 Synchronization section about synchronization, the details in the following sections can also help you understand the synchronization:

    • 8.5.1.5 Data Ready (DRDY)
    • 8.3.7.1.2 SINC3 and SINC3 + SINC1 Filter
    • 8.4.1.2 SYNC/RESET Pin

    BR,

    Dale