Design of Minimum System Interface Circuit Based on AT89C52 Single Chip Microcomputer

Single chip microcomputer STM32L151CCU6

1206RGB (single)

Test - lowercase jpg

Crystal patch M49SMD Mini S 4*7 24MHZ 24.000M

0201 package SLP0603 ESD electrostatic diode 5V one-way ESD

The AT89C52 is a low-voltage, high-performance CMOS 8-bit microcontroller from Atmel Corporation of the United States. It contains 8KB of re-writable program memory and 256B of random access data memory (RAM). The device uses Atmel's high-density, non- Volatile memory technology production, compatible with standard MCS-51 command system, on-chip configuration of general 8-bit central processing unit (CPU) and flash memory unit, powerful AT89C52 microcontroller can be flexibly applied to various control fields. The AT89C52 MCU is an enhanced version of the AT89C51 MCU and is compatible with Intel's 80C52 in terms of pinout, hardware composition, operating characteristics and command system. The AT89C52 has three package types: PDIP, PQFP/TQFP and PLCC to meet the needs of different products. When the microcontroller is working normally, it needs a clock circuit and a reset circuit. The reset of the MCU and the crystal oscillator circuit are shown in the figure.

AT89C52 and clock circuit (including crystal oscillator, capacitor C19, C20), power-on reset circuit (including R42, C5, S3, VD1, C3, R9) constitute the minimum system of the microcontroller. Among them, the crystal oscillator uses a 12MHz high-stability passive crystal oscillator, which forms an oscillator with the inverting amplifier in the AT89C52 to provide a highly stable clock signal to the CPU. Capacitors C19 and C20 can be used to fine-tune the frequency. The capacitance value is selected between 5pF and 30pF. This circuit selects 20pF. Capacitor C5 and resistor R42 form a power-on reset circuit. When the power is turned on, the power supply charges capacitor C5 and generates a high pulse at the reset end of the CPU. As long as the high level is maintained for more than two machine cycles (24 oscillation cycles). The CPU can be reset. The function of the diode VD1 is to enable the charge stored in the capacitor C5 to be quickly released when the power is turned off, so that it can be reliably reset at the next power-on. Capacitor C5 can filter out high frequency interference and prevent the MCU from being reset by mistake. The button S3 and the resistor R9 constitute a button reset circuit.