AN96667 describes how to design an accurate real-time clock for PSoC® 3, PSoC 4, and PSoC 5LP MCUs using the 50/60-Hz frequency of the mains (utility) AC power line as the time base. It also explains how to use a 32.768-kHz watch crystal as a backup time base in case of a mains power failure.
Introduction
Accurate timekeeping is a vital requirement for applications that need to perform operations at a certain time of day (for example, automated control of street lights), store the timestamp of events (such as energy meters and data acquisition devices), or display the time and date (such as a digital wall clock).These applications use a real-time clock (RTC) to generate and keep track of time. RTCs should be accurate, low cost, and low power and consume minimal printed circuit board (PCB) space.