利用2402掉电保护，保存数据，两个键值，一个是存储数据，另一个是读数据-Power-down protection by 2402, save the data, two keys, one for storing data, and the other is reading data

通用计数器C程序，采用芯片STC11F02E+74HC164，四位共阴数码管，不怕掉电，AC220V交流电检测采用频率采样而快速保存数据到EEPROM，电路简单，成本低，稳定性好。本程序完整，已经批量生产。-Universal counter C program using chip STC11F02E+74HC164, the four common cathode Digital tube, not afraid of power-down, AC220V AC detection usin

记忆存储，在单片机掉电的情况下，保存数据。-Memory storage, in the case of single-chip power-down, save the data.