Datasheet

 2010 Microchip Technology Inc. DS39951C-page 201
PIC24FJ64GA104 FAMILY
19.0 REAL-TIME CLOCK AND
CALENDAR (RTCC)
The RTCC provides the user with a Real-Time Clock
and Calendar (RTCC) function that can be calibrated.
Key features of the RTCC module are:
• Operates in Deep Sleep mode
• Selectable clock source
• Provides hours, minutes and seconds using
24-hour format
• Visibility of one half second period
• Provides calendar – weekday, date, month and
year
• Alarm-configurable for half a second, one second,
10 seconds, one minute, 10 minutes, one hour,
one day, one week, one month or one year
• Alarm repeat with decrementing counter
• Alarm with indefinite repeat chime
• Year 2000 to 2099 leap year correction
• BCD format for smaller software overhead
• Optimized for long-term battery operation
• User calibration of the 32.768 kHz clock
crystal/32K INTRC frequency with periodic
auto-adjust
19.1 RTCC Source Clock
The user can select between the SOSC crystal
oscillator or the LPRC Low-Power Internal Oscillator as
the clock reference for the RTCC module. This is con-
figured using the RTCOSC (CW4<5>) Configuration
bit. This gives the user an option to trade off system
cost, accuracy and power consumption, based on the
overall system needs.
The SOSC and RTCC will both remain running while
the device is held in Reset with MCLR
and will continue
running after MCLR
is released.
FIGURE 19-1: RTCC BLOCK DIAGRAM
Note: This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive reference
source. For more information, refer to the
“PIC24F Family Reference Manual”,
Section 29. “Real-Time Clock and
Calendar (RTCC)” (DS39696).
RTCC Clock Domain CPU Clock Domain
RTCC
RTCC Prescalers
RTCC Timer
Comparator
Alarm Registers with Masks
Repeat Counter
0.5 Sec
ALRMVAL
RTCVAL
ALCFGRPT
RCFGCAL
Alarm
Event
YEAR
MTHDY
WKDYHR
MINSEC
ALMTHDY
ALWDHR
ALMINSEC
RTCC
Interrupt
RTSECSEL<1:0>
RTCOE
10
00
01
Clock Source
1 Sec
Pin
Alarm Pulse
Input from
SOSC/LPRC
Oscillator
RTCC Interrupt Logic