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RTC_SS
20.3 RTC_SS
20.3.1 Introduction
The real-time clock is a precise timer which can generate interrupts on intervals specified by the user.
Interrupts can occur every second, minute, hour, or day. The clock itself can track the passage of real time
for durations of several years, provided it has a sufficient power source the whole time.
The basic purpose for the RTC is to keep time of day. The other equally important purpose of RTC is for
Digital Rights management. Some degree of tamper proofing is needed to ensure that simply stopping,
resetting, or corrupting the RTC does not go unnoticed so that if this occurs, the application can re-acquire
the time of day from a trusted source. The final purpose of RTC is to wake the rest of chip up from a
power down state.
Alarms are available to interrupt the CPU at a particular time, or at periodic time intervals, such as once
per minute or once per day. In addition, the RTC can interrupt the CPU every time the calendar and time
registers are updated, or at programmable periodic intervals.
20.3.1.1 Features
The real-time clock (RTC) provides the following features:
• 100-year calendar (xx00 to xx99)
• Counts seconds, minutes, hours, day of the week, date, month, and year with leap year compensation
• Binary-coded-decimal (BCD) representation of time, calendar, and alarm
• 12-hour clock mode (with AM and PM) or 24-hour clock mode
• Alarm interrupt
• Periodic interrupt
• Single interrupt to the CPU
• Supports external 32.768-kHz crystal or external clock source of the same frequency
20.3.1.2 Unsupported RTC Features
This device supports only a single RTC external wake-up event.
3621
SPRUH73H–October 2011–Revised April 2013 Timers
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