The MCP79521 SPI RTCC is highly integrated with memory and advanced features normally found in higher priced devices. By starting with a basic real-time clock, digital trimming was added for higher accuracy, a battery switchover for backup power, a timestamp to log power failures and three types of memory, which includes SRAM, EEPROM and a unique ID in a locked section of EEPROM. This ID is preprogrammed with a 48-bit MAC Address, but it can also be ordered blank for the end user to program.