An Atmega328 is used for the main microcontroller which communicates via I2C both to a DS1307 real time clock (RTC) and a TEA5767 FM module.

Here is the circuit diagram of a compact RTC module, based on the popular RTC IC DS1307, for your everyday microcontroller projects. The DS1307 serial real-time clock (RTC) is a lowpower, full ...

Like many early microcomputers, the Commodore VIC-20 did not come with an interna real-time clock built into the system.