PROSEL

Introduction

In addition to power-on reset, there are manual reset methods.

MCU reset circuit

MCU reset circuit

The capacitor is connected to the high level at the top, the resistance is connected to the ground at the bottom, and the middle is RST. This reset circuit is a high-level reset.

Its working principle is: when power is on, both ends of the capacitor are equivalent to a short circuit, so the RST pin is high, and then the power supply charges the capacitor through the resistor, and the voltage at the RST terminal slowly drops to a certain level, which is low level , The microcontroller starts to work normally.

First, RST is automatically reset when it maintains a high level for more than two machine cycles

1. Power-on reset: At the moment of power-on, the capacitor charging current is the largest, the capacitor is equivalent to a short circuit, and the RST terminal is at high level, automatically reset; when the voltage across the capacitor reaches the power supply voltage, the capacitor charging current is zero, and the capacitor is equivalent to an open circuit. The RST terminal is low, and the program runs normally.

2. Manual reset: First, after power-on reset, when the button is pressed, RST is directly connected to VCC to form a reset at a high level, and the electrolytic capacitor is short-circuited and discharged; when the button is released, VCC charges the capacitor, and the charging current is at On the resistance, RST is still high and it is still reset. After charging is completed, the capacitor is equivalent to an open circuit, and RST is low and it works normally.