The MSM6542 is a perpetual-calendar-based real time clock with an alarm function which can read and write data in units of seconds. It can be connected to various buses and can function as a peripheral IC of a microcomputer. The clock ranges are seconds, minutes, hours, days, months, years, and days of the week. The alarm ranges are seconds, minutes, hours, days, months, and days of the week. An event trigger is generated when the time matches the specified time and an alarm occurs or when the clock counter generates a carry. The interrupt and pulse outputs are provided for each of an alarm and a carry. An interface with a microcomputer is implemented by four data bus pins, four address bus