The MCP79510-I/MS is a SPI Real-time Clock and Calendar (RTCC) IC, 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 blank unique ID in a locked section of EEPROM. The ID is blank in this device, but can also be ordered with a 48 or 64-bit MAC address. Along with a 32,768kHz crystal, this RTCC tracks time using several internal registers and then communicates the data over a 5MHz SPI bus that is fast enough to support a programmable millisecond alarm. As part of the power sense circuit, a time saver function is implemented to store the time when main power is lost and again, when power is restored to log the duration of a power failure.