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LP-MSPM0C1104: Automation

Haibo Xu
Prodigy 130 points
Part Number: LP-MSPM0C1104


Hello Expert：

The MSPM0C1103QDYYRQ1 microcontroller's pin4 has both reset and I2C functions, and reset is definitely necessary.

1.If I still want to use the I2C function, can pin4 use both reset and I2C functions at the same time?

The reset pin only has external reset input during debugging.

During normal operation, only when powered on needs to use pin4 as the reset pin. The current application does not have RST signal input to the microcontroller.

After resetting, pin4 is used as I2C. Is this okay?

2.In addition, the reset function manual recommends 47K, and the pull-up resistance of I2C is 2.2K. Is it impossible to share pin4 at the same time?

 i2C SPEED 400KHz

Can the pull-up resistance of NRST be changed to 2.2K and remove the capacitor？

3.If it is in the case of LIN SBC, the LIN SBC will output a reset signal to the microcontroller,
Is it possible that reset and I2C cannot be shared, and during normal system operation, the pin also needs to be configured with reset function?

  

  • 0
    TI__Guru 71216 points

    Hello Haibo,

    According to the TRM, it is not possible to use the NRST pin for both RESET and I2C.  You select one or the other.  The NRST functionality is set during the system boot (before application runs) and can not be changed from within the application.

    So, during a POR, an external pull up is required in order for the MCU to start operating. Although the datasheet says you need a 47K resistor and capacitor on this pin, this is true when the NRST pin's function is for RESET.  In your case, you will have a 2.2K pull up resistor, so this satisfies the pull up resistor requirement.  You also don't want to put any capacitor on this pin, as this will add too much capacitance on the SCL line.

    After the POR, the system boot code will disable the NRST pin to allow the application to assign the I2C functionality. 

    So in summary, no, you cannot use the NRST pin for both RESET and I2C at the same time.

  • 0 in reply to Dennis Lehman
    Prodigy 130 points

    Hello Dennis

    Thank you for your reply.