Today I share the circuit board design of a 51 single-chip microcomputer minimum system (schematic diagram + PCB)
The technical manual above makes the following requirements for the minimum system of 51 single-chip microcomputer:
The download circuits mainly include the following:
Download using RS-232 converter: (R1OUT—P3.0; T1IN—P3.1):
USB to serial power supply circuit:
U8-Mini for ISP download:
Now commonly used is the cold start downloader: the circuit structure is relatively simple, and this download method is also used in my design:
The schematic diagram of the circuit is as follows:
The power supply is input through a 6-pin self-locking switch, and a diode is connected in series to prevent the reverse connection of the power supply; C1 filters the input power supply.
The 7805 three-terminal linear regulated power supply is used to stabilize the voltage and then supply power to the MCU, in which D2 prevents the LM7805 from being broken down. C2, C3 and C4, C5 perform input and output filtering.
Download circuit:
Manual reset and power-on self-reset combined reset circuit:
Crystal oscillator circuit:
The PCB layout is shown in the following figure:
The 3D view is shown in the image below;
