The Portable System Controller is a circuit which incorporates many of the functions necessary for low power portable products integrated into one chip. The DS1677 provides a Real Time Clock, NV RAM controller, micro-processor monitor, powerfail warning, and a 3channel, 8bit analogtodigital converter. Communication with the DS1677 is established through a simple 3wire interface. The Real Time Clock (RTC) provides seconds, minutes, hours, day, date, month, and year information with leap year compensation. The RTC also provides an alarm interrupt. This interrupt works when the DS1677 is powered by the system power supply or when in battery backup operation so the alarm can be used to wake up a system that is powered down.