The Real Time Clock (RTC) keeps track of time of day, to an accuracy of one hundredth of a second with a 100 Hz clock or one second with 1 Hz clock. The RTC has calendar functionality keeping track of the day, month and year. An alarm register allows comparison of month, date, hour, minute, second and hundredthsecond. This can be used, for example, to generate an alarm at 12:37 on the 15th of every month. The RTC can also generate an interrupt on the detection of a specific event. The event can be time or calendar based with the interrupt being triggered on a roll-over into a new month, date, hour, minute, second or hundredth of second.