AM1808_1008 Datasheet, PDF (241/264 Pages) Texas Instruments – AM1808 ARM Microprocessor

AM1808
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SPRS653A – FEBRUARY 2010 – REVISED APRIL 2010
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
Counter
32 kHz
Oscillator
Compensation
Week
Days
Oscillator
Seconds
Minutes Hours
Days
Months
Years
Alarm
Timer
Figure 6-82. Real-Time Clock Block Diagram
Alarm
Interrupts
Periodic
Interrupts
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Peripheral Information and Electrical Specifications 241
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