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Chapter 23
Real-Time Clock (RTC)
This chapter discusses how to operate and program the real-time clock (RTC) module that maintains the
system clock, provides stopwatch, alarm, and interrupt functions, and supports the following features:
•
Full clock—days, hours, minutes, seconds
•
Minute countdown timer with interrupt
•
Programmable daily alarm with interrupt
•
Sampling timer with interrupt
•
Once-per-day, once-per-hour, once-per-minute, and once-per-second interrupts
•
Operation at 32.768 kHz or 32 kHz, or 38.4 kHz (determined by reference clock crystal)
As shown in the RTC block diagram (Figure 23-1), the real-time clock module consists of the following
blocks:
•
Prescaler
•
Time-of-day (TOD) clock counter
•
Alarm
•
Sampling timer
•
Minute stopwatch
•
Associated control and bus interface hardware
MOTOROLA
Real-Time Clock (RTC)
23-1
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