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MSP430G2744: I2C tSU;STO with FAST MODE.

Hitoshi Sugawara
Mastermind 18640 points
Part Number: MSP430G2744

Hi experts,
According to the I2C specification, I2C tSU; STO is 0.6us (min) for FAST MODE 400KHz.
In the datasheet www.ti.com/lit/SLAS892, tSU; STO is 4 us (min).

I believe that it should be 0.6 us (min) if fSCL>100KHz.
Could you please double check?

In addition, tSU; STA in the datasheet is 0.6 us (min) which follows the I2C spec.
Thank you very much for your check.
Best regards,
Hitoshi

  • 0
    TI__Mastermind 26420 points
    Hello Hitoshi,

    Is the MSP430 the master or slave in the application? Is your customer seeing issues with stop conditions?

    I looked at the datasheet and I understand your question. As the datasheet spec states, the tSTO was only specified for I2C Normal Mode timings on this family.

    My guess is that this is because this spec for the stop bit is a small concern. In Master mode, we generate the stop condition. In slave mode, even if we don't register the stop immediately, we still should or we will detect a repeated start condition. Either way, the application should be able to handle this use case.

    Thanks,
    JD
  • 0 in reply to JD Crutchfield
    TI__Mastermind 18640 points
    Hi JD,
    The MSP430 is slave in this application.
    The I2C master has the fixed tSU; STO 1 us. It is hardly changed.
    There have been no issues so far, but my customer is concerned about any failure.

    "In slave mode, even if we don't register the stop immediately, we still should or we will detect a repeated start condition. "
    This could correct I2C communication even though the MSP430 fails to detect STOP condition.
    Am I correct?

    Thank you for your quick support.
    Best regards,
    Hitoshi
  • 0 in reply to Hitoshi Sugawara
    TI__Mastermind 26420 points
    Hey Hitoshi,

    Yes, in the use cases I can think of this should correct I2C communication. Might depend slightly on the applications state machine, but it should be easy to implement that a repeated start = normal start, etc.

    Honestly, I suspect the device will detect the stop bit just fine, but that we just didn't spec it or characterize it on the F2xx series of devices. On the F4x and F5xx devices and forward we do split the spec the tSU.STO to be .6us in Fast mode.

    Thanks,
    JD
  • 0 in reply to JD Crutchfield
    TI__Mastermind 18640 points
    HI JD,
    Thank you for your kind explanation.
    Will convey it to the customer and take care of it.
    Best regards,
    HItoshi

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