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DIFFERENT WAYS TO RESET ST7 MICROCONTROLLER

RESET pin connected externally form a voltage divider. Hence, this pull-down resistor should

be selected in such a way ensuring the voltage at the RESET pin is sufficiently low to reset the

microcontroller. Keeping this in mind the recommended value for this pull-down resistor is 10K

or lower, thus keeping the voltage at the RESET pin less than (1/3)*Vdd.

Figure 6. Waveform of Power-on-Reset with PNP Reset Circuit (Transistor biased with

Potential divider)

When you require more precision in terms of voltage threshold then you can replace resistor

R2 with a Zener diode. In this case the threshold of the circuit would be equal to the break-

above circuit.

Figure 7. Transistor based External Reset circuit with Zener diode to bias the transistor

RESET

R1= 33K, R2=150K

Threshold= 3.3V @Vbe = 0.6V

1K

R1

10K

RESET