Datasheet

© 2009-2011 Microchip Technology Inc. DS61156G-page 151
PIC32MX5XX/6XX/7XX
21.0 REAL-TIME CLOCK AND
CALENDAR (RTCC)
The PIC32 RTCC module is intended for applications
in which accurate time must be maintained for
extended periods of time with minimal or no CPU
intervention. Low-power optimization provides
extended battery lifetime while keeping track of time.
A simplified block diagram of the RTCC module is
illustrated in Figure 21-1.
Following are some of the key features of this module:
• Time: hours, minutes and seconds
• 24-hour format (military time)
• Visibility of one-half second period
• Provides calendar: Weekday, date, month and
year
• Alarm intervals are configurable for half of a
second, one second, 10 seconds, one minute, 10
minutes, one hour, one day, one week, one month
and one year
• Alarm repeat with decrementing counter
• Alarm with indefinite repeat: Chime
• Year range: 2000 to 2099
• Leap year correction
• BCD format for smaller firmware overhead
• Optimized for long-term battery operation
• Fractional second synchronization
• User calibration of the clock crystal frequency with
auto-adjust
• Calibration range:
±0.66 seconds error per month
• Calibrates up to 260 ppm of crystal error
• Requirements: External 32.768 kHz clock crystal
• Alarm pulse or seconds clock output on
RTCC pin
FIGURE 21-1: RTCC BLOCK DIAGRAM
Note 1: This data sheet summarizes the features
of the PIC32MX5XX/6XX/7XX family of
devices. It is not intended to be a
comprehensive reference source. To
complement the information in this data
sheet, refer to
Section 29. “Real-Time
Clock and Calendar (RTCC)”
(DS61125) in the “PIC32 Family
Reference Manual”
, which is available
from the Microchip web site
(www.microchip.com/PIC32).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
Section 4.0 “Memory Organization” in
this data sheet for device-specific register
and bit information.
Seconds Pulse
RTCC Prescalers
RTCC Timer
Comparator
Compare Registers
Repeat Counter
YEAR, MTH, DAY
WKDAY
HR, MIN, SEC
MTH, DAY
WKDAY
HR, MIN, SEC
with Masks
RTCC Interrupt Logic
Alarm
Event
32.768 kHz Input
from Secondary
0.5s
Alarm Pulse
RTCC Interrupt
RTCVAL
ALRMVAL
RTCC Pin
RTCOE
Oscillator (S
OSC)