What is the minimum system of 51 microcontroller

1. What is 51 microcontroller

The 51-core microcontroller refers to the collective name for microcontrollers that are compatible with Intel's 8051 instruction system; in the decades since its birth, it has become a market-tested and mature chip product. At present, there are many 51 microcontroller manufacturers in China, and there are also many special-purpose microcontrollers with 51 cores used in various scenarios.

51 microcontroller internal frame:

The following takes the STC89C52 microcontroller as an example. Its internal overall structure and its basic characteristics are as follows:

8-bit CPU, 4-8k bytes ROM, 128 bytes RAM, 21 special function registers, 32 I/0 lines, addressable 64 bytes of external data, program storage space, 2 16-bit timer counters Interrupt structure: A bit processor with two priority levels, five interrupt sources, a full-duplex serial port, bit addressing (i.e., bit operation on the register) function, and can perform logical operations on a bit-by-bit basis.

In addition to 128 bytes of RAM, 4-8k bytes of ROM and interrupts, serial ports and timer modules, there are also 4 groups of I/0 ports PO~P3, and the rest is the entire composition of the CPU. Each part of the microcontroller is organically connected through an internal bus.

2. What is the minimum system of 51 microcontroller?

The minimum system of 51 microcontroller is the smallest hardware circuit that allows the microcontroller to work normally. It mainly includes 51 microcontroller chip, crystal oscillator circuit, reset circuit and power supply circuit.

in:

(1) The RST pin is connected to the reset circuit;

(2) XTAL1 and XTAL2 are connected to the crystal oscillator circuit;

(3) VCC and GND are connected to +5V power supply;

(4) Connect the EA pin to +5V or leave it unconnected (connect it to +5V or leave it unconnected, and the microcontroller will start executing the program internally after resetting; connect it to GND, and the program will be executed externally); the ALE and PSEN pins can be left unconnected.

(5) The other 32 pins are the input and output interfaces of the microcontroller.

3. Crystal oscillator circuit

The crystal oscillator circuit is the clock source of the microcontroller, providing a reference source for the microcontroller to execute programs. Its cycle determines the speed at which the microcontroller executes programs.

The crystal oscillator circuit is connected to the inverting amplifier inside the microcontroller to form an oscillator with a specific frequency, providing a stable high-frequency oscillation signal for the microcontroller. For a 12MHz solution, if the load capacitance of the crystal oscillator is 20pF, two external capacitors C1 The appropriate value for C2 is 27pF to 33pF.

4.Reset circuit

When the microcontroller is powered on, a reset signal is needed to put the internal registers, program counter and other internal states of the microcontroller in the initial state. Then the PC counter of the microcontroller can start executing the program in the most initial state.

The 51 microcontroller is a high-level reset, and its reset circuit is an RC circuit, which is composed of a capacitor and a resistor in series. When the system is powered on, the capacitor begins to charge, which is equivalent to a short circuit of the capacitor, and the RST pin is in a high-level state. The microcontroller enters reset state. When the capacitor is fully charged, it is equivalent to an open circuit and the RST pin is in a low level state. This completes the reset operation of the microcontroller.

The K1 button provides a manual reset function. When the button is pressed, the RST pin is high level (capacitor discharge). After the button is released, the RST pin is low level (capacitor charging).

5.Power interface

The final power supply provides +5V power for the minimum system of the microcontroller. Its P1 is the power interface, and S1 is a self-locking switch that can perform power-on and power-off operations. D1 is the power indicator light, allowing users to confirm whether the system is powered on or off during use.