用51单片机写的时钟，用1602显示，附带闹钟功能，每隔5秒会由串口发送一次时间到电脑显示，且可通过串口和按键改时间-With 51 MCU write clock, with the 1602 show, with alarm function, every five seconds a time by the serial port to send to the computer display, and can be changed through the serial port and