STC89C52 minimum system

1. Reasons for design
This project is designed to train new students from the Electronic Technology Association of our school. It is hoped that through the training of the 51 microcontroller system board, students will deepen their understanding of the 51 microcontroller hardware and lay the foundation for future programming learning.
2. Project Introduction
The chip used in this design is STC89C52RC. This chip is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of Flash program memory and 512 bytes of RAM data memory. The instruction code is fully compatible Traditional 8051 microcontroller. Cheap, high-speed and reliable, low power consumption, strong anti-interference. This design also adds a USB to serial port chip, which provides convenience for downloading and debugging.
3. The onboard resource
master control is STC89C52,
a total of 5 LEDs, 3 for running water light function, 1 for power indicator, 1 for download indicator,
a total of 3 buttons, 2 for ordinary buttons, 1 for reset button
and one A toggle switch is used for downloading cold boot.
A USB to serial port chip is used for level conversion when downloading programs through the serial port.
A TYPE-C interface is used for power supply and program burning.
Four 8PIN headers are used to draw out microcontroller resources.
Two 4PIN headers. Used to lead out 5V and GND
4. PCB design instructions
adopt a four-layer board design, in which the upper and lower layers are used for signal lines, and the middle layer one and two are used for 5V and GND.
The middle layer 1 is covered with 5V copper, and the middle layer 2 is covered with GND copper.
The filter capacitor should pay attention to the current flow direction and try to be as close as possible to the component that needs to be filtered.
The crystal oscillator should be as close to the chip as possible, and no traces should be routed at the bottom to prevent signal crosstalk.
Prioritize routing in straight lines, and use obtuse angles or arcs where corners are needed.
5. Circuit model
6. Physical display