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AM1808
SPRS653E – FEBRUARY 2010 – REVISED MARCH 2014
6.31 Real Time Clock (RTC)
The RTC provides a time reference to an application running on the device. The current date and time is
tracked in a set of counter registers that update once per second. The time can be represented in 12-hour
or 24-hour mode. The calendar and time registers are buffered during reads and writes so that updates do
not interfere with the accuracy of the time and date.
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.
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
•
Separate isolated power supply
Figure 6-82
shows a block diagram of the RTC.
RTC_XI
XTAL
RTC_XO
Oscillator
238
Peripheral Information and Electrical Specifications
Oscillator
Counter
Compensation
32 kHz
Seconds
Minutes
Figure 6-82. Real-Time Clock Block Diagram
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Week
Days
Hours
Days
Months
Alarm
Timer
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Years
Alarm
Interrupts
Periodic
Interrupts
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