The minimum system circuit of 51 single-chip microcomputer (circuit diagram + experience explanation)

 Here we take the 89c5x microcontroller as an example.

First look at the circuit I drew using protel.

 This is a board I soldered. It is roughly soldered according to the circuit, with an additional 74573 and digital tube.

There are two ways to get the 5V power supply here. One is from the USB port of the computer (this is explained in the article about the spi download line)

The second is to obtain it from 220v AC power. How to obtain 5v power will be introduced in the next article. Today we will introduce the minimum system of the microcontroller.

I connected a light-emitting diode to the 5V output of the circuit. I forgot to connect a 1k resistor in series here. Don't forget to use it when you use it.

It is used to limit the current, otherwise the LED will burn out. I usually connect it outside the switch, so that I can find out if the power supply is connected in reverse, so as not to cause

Reverse power connection may cause risk of circuit burnout.

It doesn’t matter if it doesn’t work overnight. I connected a diode behind the switch to prevent the power supply from being reversed. This way, even if the circuit is blocked, no problems will occur.

Please note that the vcc used by the microcontroller is drawn from the place where I marked vcc in the picture, because it can be controlled by a switch there.

Crystal oscillator circuit, I usually use 11.0592 and 22.1184 crystal oscillators. The higher the oscillation frequency, the faster the MCU runs. This will be in the delay program editing

It will be reflected at this time. As long as c1 and c2 are between 15pf and 22pf, it is generally ok.

There are many kinds of reset circuits. Here is the one I use most often. When the switch is not pressed, reset is low level, the capacitor is fully charged, and when the key is pressed

The capacitor is discharged instantly, the voltage across the capacitor is 0, and then it is slowly charged, and the reset pin receives a high pulse, which resets the microcontroller. The circuit component parameters are shown in the figure.

As we all know, the p0 port is different from the other three ports in that it has a very weak driving capability and cannot function without a pull-up resistor. Generally, a 10k resistor is sufficient.

After pulling up, p0 outputs 1, and the current is provided by the pull-up power supply. When p0 is low, the power supply current flows into the pin.

In addition, if the microcontroller is used to make a common circuit, I suggest soldering an 8-pin socket on each pin like I did.

It is easy to expand and use, very convenient. There are eight-pin and eight-pin cables and slots on the market, which are very easy to use.