DS1307 modules are readily available, and often the cheapest RTC solution available at most outlets. The DS3234 has the distinction of using an SPI interface instead of I2C. It also packs in 256 ...

only implementation of a synchronization core allowing to read and write a I2C Realtime Clock (RTC) like the DS1307 or MCP7941x. Access to the RTC is done from the FPGA without software interaction.