The DS28DG02 is a 2-kb SPI EEPROM with PIO, real-time clock (RTC), reset, battery monitor and watchdog that combines several functions needed in portable equipment and embedded applications. This application note supplements the product’s data sheet, gives additional information on the SPI interface and its write-protection scheme, and shows how to use the device’s 12 PIOs and the RTC alarm function. The document also includes guidance on battery selection, shielding of the RTC crystal pads, and the software response to alarm events.