Dallas-Timekeeping-ICs-Maxim-DS1307-Real-Time-Clock-I2C-Serial-Interface-RTC-Features-56-Byte-Battery-Backed-General-Purpose-RAM-250ns-Data-Setup-Time-100k Hz-Clock-Frequency-4-5V-to-5-5V-Supply-Voltage-0-C-to-70-C-8-DIP-Case-The-DS1307-Serial-Real-Time-Clock-is-a-Low-power-Full-BCD-Clock-Calendar-with-56-Bytes-of-NVDs 1307-Timekeeper-with-BCD-Rtc