单片机最小系统（Single chip microcomputer minimum system）.doc

单片机最小系统（Single chip microcomputer minimum system） Single chip microcomputer minimum system In intelligent instrument and meter, the control core of microprocessor, and single-chip microcomputer with high performance, high speed, small volume, low cost, stable and reliable and is widely used, is the first choice for designing intelligent instrumentation microcontrollers, single-chip microcomputer combined with simple interface circuit can constitute a single chip microcomputer minimum system, it is the basis of intelligent instrument and meter, and measurement and control. An important part of monitoring. I. system function requirements: 1. Display number: 6. 2. Keypad number: 16. 3. The initialization status displays P. 3. Can input and display hexadecimal number 0 -- f. Ii. Overall scheme of the system: 1. Single chip microcomputer can adopt AT89C51, AT89C52, AT89S52, fosc = 12MHz. 2. Design of clock circuit and reset circuit. Write system initializing main program, key scan subroutine, display subroutine, and other required subroutines. Iii. Hardware system design: 1. Clock circuit The design of the systems clock circuit is the internal way of using the internal oscillator circuit of the chip. AT89 microcontroller has a high gain inverting amplifier used to form the oscillator. Pins XTAL1 and XTAL2 are the input and output terminals of this amplifier. This amplifier forms a self-excited oscillator together with an external crystal resonator as a feedback element. The external crystal resonators and capacitors C1 and C2 form parallel resonant circuits, which are connected to the feedback loop of the amplifier. Although the value of external capacitance is not strictly required, the size of capacitance can affect the frequency of oscillators, stability of the oscillators, the speed of vibration and the stability of temperature. Therefore, the crystal oscillator of this system circuit has a value of 12MHz, and the capacitance should be as selective as possible to the