单片机开发板的电路图 包含 PCB。。。。U1=89C51 U2=555 U3=MAX232 U4=24C01 U6＝X25045看门狗 X1=共阳数码管 -Single-chip development board contains the circuit PCB. . . . U1 = 89C51U2 = 555U3 = MAX232U4 = 24C01U6 = X25045 watchdog X1 = total yang digital tube

Running LED display, timing is controlled withthe helpof 555 timer. microcontroller used is 89c51

555定时器基于STC 89C51单片机制作声响和光电报警装置。-555 timer-based STC 89C51 microcontroller produced audible alarm device.