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Original question:

MSP430I2021: RST Pin Handling

MSP430I2021: When RST/NMI/SBWTDIO is held at Low output

O.H
Genius 5960 points
Part Number: MSP430I2021

Hi experts,

Please let me check the RST/NMI/SBWTDIO pins.

Q1: Am I right in thinking that when the RST/NMI/SBWTDIO pin operates in reset mode (or NMI mode), it functions as an input and not as an output?

In general, I think the RST/NMI function works as an input. Also, I don't know the internal structure from the answer to the original question, but I believe it does not work as an output. However, since it is a dual-purpose pin with SBWTDIO function, it seems to work as input/output from the data sheet, so let me confirm this.

Q2: If the RST/NMI/SBWTDIO pin also functions as an output in reset mode, is there a case where the RST/NMI/SBWTDIO pin outputs Low?

Best regards,
O.H

  • 0
    TI__Mastermind 28955 points

    Hello,

    Yes, the RST/NMI pin always functions as a input pin.  I would never expect it to drive the output low unless it was somehow damaged.  

    The question about SBW is interesting because SBWTDIO is bi-directional.   I guess there is a pull-down circuit multiplex in if the JTAG interface is active.  I can't recall this ever interfering with the RST line outside of programming, but I guess it's technically possible.

    Are you seeing a specific issue of some sort? 

    Thanks,

    JD  

  • 0 in reply to JD Crutchfield
    Genius 5960 points

    Hello DJ,

    Thanks for the reply.

    JD Crutchfield said:

    Yes, the RST/NMI pin always functions as a input pin.  I would never expect it to drive the output low unless it was somehow damaged.  

    The question about SBW is interesting because SBWTDIO is bi-directional.   I guess there is a pull-down circuit multiplex in if the JTAG interface is active.  I can't recall this ever interfering with the RST line outside of programming, but I guess it's technically possible.

    I understood.

    JD Crutchfield said:
    Are you seeing a specific issue of some sort? 

    Related to the thread below, there is a problem with UART communication becoming unstable at high temperatures. (Data may not be observed on the communication line.)

    e2e.ti.com/.../msp430i2021-circuit-configuration-of-dco-and-relationship-between-external-resistance-value-and-oscillation-frequency

    According to the customer's investigation, sometimes no data is observed when a measurement device is connected to the communication line; when the RST/NMI pin is connected to the measurement device, it is fixed to Low, and shorting the RST/NMI pin to VCC restores the device.

    We have not been able to identify a clear cause, and since we are checking the frequency response of the DCO and the processing and operation of the RST/NMI pins. This is why I asked this question.

    Best regards,
    O.H

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