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Rokyy
Rokyy
Associate
Jul 12, 2019 3:01 AM UTC
Solved

stm8af5288 nrst pin 1K resistance?

Will the external 1k resistor of the nrst pin have an effect?

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    Sisto Zànier
    Sisto ZànierBest answer
    Senior
    Jul 16, 2019 7:14 PM UTC

    In the worst case, the internal pull-up resistor may have a minimum value of about 30K , so when you generate a Reset, the effective voltage level of NRST input, will be (VCC/31K)*1K = 0,106V

    This value is much lower than the maximum level of 0.8V, required to reset the STM8Lxx.

    Therefore all voltages below this value will generate a microcontroller reset.

    Instead, I don't know how your MCU reset is generated, but if you really want to insert a 1K resistor in series at the NRST input, it would be better if it was placed before the 100nF by-pass capacity.

    In this way you would also have a certain filter effect.

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    Sisto Zànier
    Sisto ZànierBest answer
    Senior
    Jul 16, 2019 7:14 PM UTC

    In the worst case, the internal pull-up resistor may have a minimum value of about 30K , so when you generate a Reset, the effective voltage level of NRST input, will be (VCC/31K)*1K = 0,106V

    This value is much lower than the maximum level of 0.8V, required to reset the STM8Lxx.

    Therefore all voltages below this value will generate a microcontroller reset.

    Instead, I don't know how your MCU reset is generated, but if you really want to insert a 1K resistor in series at the NRST input, it would be better if it was placed before the 100nF by-pass capacity.

    In this way you would also have a certain filter effect.

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