[Daily circuit diagram] 1, based on AT89C52 microcontroller minimum system interface circuit "turn"

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Come from:http://www.21ic.com/dianlu/basis/interface/2015-04-21/621607.htm

AT89C52 is a low-voltage, high-performance CMOS 8-bit microcontroller produced by Atmel Inc., which contains 8KB of reusable program memory and 256B of random Access Data memory (RAM), using Atmel's high-density, Non-volatile storage technology, compatible with the standard MCS-51 instruction system, on-chip configuration of the general 8-bit central processing unit (CPU) and flash memory units, the powerful AT89C52 microcontroller can be flexibly applied to a variety of control areas. AT89C52 single chip microcomputer belongs to the enhancement of at89c51 single chip microcomputer, and the 80c52 of Intel Corporation is compatible with the pin arrangement, hardware composition, working characteristic and instruction system. AT89C52 has Pdip, PQFP/TQFP and PLCC three kinds of package form, in order to adapt to the needs of different products MCU normal work, need to have a clock circuit and a reset circuit. Single-chip microcomputer reset, crystal oscillator circuit .

AT89C52 and clock circuit (including crystal oscillator, capacitance C19, C20), power-on reset circuit (including R42, C5, S3, VD1, C3, R9) constitute a microcontroller minimum system. Among them, the crystal oscillator chooses 12MHz high stable passive crystal oscillator, it and the reverse amplifier in the at89c52 form the oscillator, provides the CPU the high stable clock signal. Capacitor C19, C20 can play the role of frequency tuning , capacitance value between 5pf~30pf choice, this circuit selected 20pF. The capacitance C5 and the resistor R42 form The power-on reset circuit . when the power is on, the power supply C5 the capacitor and generates a high pulse at the reset end of the CPU. As long as the high-level maintenance time is greater than two machine cycles (24 oscillation cycles). The CPU can be reset. The function of the diode VD1 is that when the power is cut off, the electric charge stored in the capacitor C5 can be released quickly so that the next power-up is reliably reset. Capacitor C5 can filter out high-frequency interference to prevent the single-chip computer from resetting by mistake. key S3 and resistor R9 form the key reset circuit .

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[Daily circuit diagram] 1, based on AT89C52 microcontroller minimum system interface circuit "turn"