ANALOG DEVICES DS17887-5+

The DS17887-5+ is a real time clock in 24 pin EDIP package. It provides a real time clock/calendar, one time of day alarm, three maskable interrupts with a common interrupt output, a programmable square wave and 114 bytes of battery-backed NV SRAM. It integrates a quartz crystal and lithium energy source. The power control circuitry allows the system to be powered on by an external stimulus such as a keyboard or by a time and date (wake-up) alarm. The active-low power-on reset output pin is triggered by one or either of these events and is used to turn on an external power supply. This pin is under software control so that when a task is complete, the system power can shut down. The date at the end of the month is automatically adjusted for months with fewer than 31 days including correction for leap years. A precision temperature-compensated circuit monitors the status of VCC. If a primary power failure is detected, the device automatically switches to a backup supply.