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DS90UB954-Q1: I2C SDA, SCL

Dustin Yim
Expert 4096 points
Part Number: DS90UB954-Q1
Other Parts Discussed in Thread: ALP

Hi Expert,

I looked into the I2C (SCL, SDA) data of DS90UB954 by using ALP tool like below.

click Apply (*The data maybe different with image upper.)

 As you can see there are two SCL part(18bits, 18bits).

Frist : Start/Slave address, R/W /ACK(0)/ Offset Address/ACK(0)/ Stop

Second : Start/Slave address, R/W /ACK(0)/ DATA/ NACK(1)/ Stop

I have two questions.

1. The reason of narrow width pulse. Would It be matter?

2. If I regard the narrow pulse as R/W = 1, this operation is Read. Is it right?

(+ also second data part seems to include slave address as well as data. This format is for read operation.)

Thank you.

  • 0
    TI__Expert 4160 points

    Dear Dustin,

    Thank you for your question and supporting image!

    To clarify, you are trying to read from your device and have noticed an abnormal narrow pulse after the first device address, is that correct?

    I have taken a closer look at the image you have provided and annotated it shown here:

    It looks like the narrow pulse occurs when the clock is down. It shows up after the R/W pulse and before the ACK pulse. It should not affect you from reading the device. Attached is the I2C protocol below.

    1. No, the narrow width pulse should not matter. Are you able to correctly read from the device's register?

    2. No, the R/W should 0 after the first Device Address if you are trying to read from the device. The narrow pulse looks like it is showing up after the R/W pulse and before the ACK pulse.

    I hope this help. If you have any further questions, please reach out.

    Best Regards,

    William Yi