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Original question:

MSP430I2021: About Designing Around RST Pins

MSP430I2021: RST Pin Handling

O.H
Genius 5635 points
Part Number: MSP430I2021

Hi experts,

My customer  has a question about the RST pin.
Could you tell me about the following items?

1)Is it okay to connect the RST pin directly to the VDD level?

2)If the RST pin is directly connected to the VDD level, will CPU reset work properly when an interrupt for a non-maskable reset request such as WDT interrupt is received?

3)Is there an internal circuit for the RST pin of the MSP 430I2021?
I checked it in the thread below, but I couldn't get an answer, so I will check it again.
https://e2e.ti.com/support/microcontrollers/msp430/f/166/p/903189/3338653#3338653

Best Regards,
O.H

  • 0
    TI__Genius 14165 points

    Hi O.H

    according datasheet you should connected RST pin via a pull up of 47 kOhm to DVCC and also apply a capacitor of at least 2.2nF due to following reasons prevent a short current on RST in pulling it low (resistor limits current) and apply a certain slow slope to RST pin during powering up giving the device a delay for release during power up.
    See datasheet:

    So for test purpose if device is properly powered up you can connect it to DVCC it will work but again it is not the specified and recommended way of using it.
    If RST pulled high all interrupts mask able or non mask able would work. The only thing which does not work is that you can have edges on RST/NMI pin to trigger a RST pin NMI interrupt because you would generate a short as mentioned above.

    So finally there is a Schmidt trigger or in simple words a comparator connected detecting if the RST pin is high or low to reset or release the device or to trigger an NMI. Also ESD structurs are connected.

    So maybe you can share you problem so that we can help you properly. Do I understand right that you get unintended RESETS during EMC noise?

  • 0 in reply to Dietmar Walther
    Genius 5635 points

    Hi Dietmar Walther,

    >So maybe you can share you problem so that we can help you properly. Do I understand right that you get unintended RESETS during EMC noise?Yes.However, the information I know is currently only in the following thread.
    https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/903189

    First, let them try "4. Use recommended reset circuit for better reset pin protection" in the MSP430 System ESD Troubleshooting Guide.
    We will contact you again when we get more information.

    Thank you for your support.

    Best Regards,
    O.H

  • 0 in reply to O.H
    TI__Genius 14165 points

    O.H,

    another very good document on EMC robus design is the following it also provides a lot of details how noise distributes through your PCB:

    http://www.ti.com/lit/an/slaa932/slaa932.pdf?&ts=1589439156947

  • 0 in reply to Dietmar Walther
    TI__Genius 14165 points

    Hi,

    were you able to resolve the problem with the help of the above mentioned Apps Notes?

  • 0 in reply to Dietmar Walther
    Genius 5635 points

    Hi,

    I contacted the information you gave me, but there is no response from the customer.

    Is it better to recreate the thread when new information is received?

    Best Regards,
    O.H

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