The ISL1220 device is a low power real time clock with timing and crystal compensation, clock/calendar, power fail indicator, periodic or polled alarm, intelligent battery backup switching, battery-backed user SRAM and separate FOUT and IRQ outputs.
The oscillator uses an external, low-cost 32.768kHz crystal. The real time clock tracks time with separate registers for hours, minutes, and seconds. The device has calendar registers for date, month, year and day of the week. The calendar is accurate through 2099, with automatic leap year correction.