PIC18F87J90 Datasheet, PDF (169/450 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F87J90 FAMILY
FIGURE 15-5:
ALARM MASK SETTINGS
Alarm Mask Setting
AMASK<3:0>
0000 – Every half second
0001 – Every second
Day of the
Week Month
Day
0010 – Every 10 seconds
0011 – Every minute
0100 – Every 10 minutes
0101 – Every hour
0110 – Every day
0111 – Every week
1000 – Every month
1001 – Every year⁽¹⁾
d
dd
mm
dd
Note 1: Annually, except when configured for February 29.
Hours Minutes Seconds
s
ss
m
ss
mm
ss
hh
mm
ss
hh
mm
ss
hh
mm
ss
hh
mm
ss
When ALRMCFG = 00 and the CHIME bit = 0
(ALRMCFG<6>), the repeat function is disabled and
only a single alarm will occur. The alarm can be
repeated up to 255 times by loading the ALRMRPT
register with FFh.
After each alarm is issued, the ALRMRPT register is
decremented by one. Once the register has reached
‘00’, the alarm will be issued one last time.
After the alarm is issued a last time, the ALRMEN bit is
cleared automatically and the alarm turned off. Indefinite
repetition of the alarm can occur if the CHIME bit = 1.
When CHIME = 1, the alarm is not disabled when the
ALRMRPT register reaches ‘00’, but it rolls over to FF
and continues counting indefinitely.
15.3.2 ALARM INTERRUPT
At every alarm event, an interrupt is generated. Addi-
tionally, an alarm pulse output is provided that operates
at half the frequency of the alarm.
The alarm pulse output is completely synchronous with
the RTCC clock and can be used as a trigger clock to
other peripherals. This output is available on the RTCC
pin. The output pulse is a clock with a 50% duty cycle
and a frequency, half that of the alarm event (see
Figure 15-6).
The RTCC pin also can output the seconds clock. The
user can select between the alarm pulse, generated by
the RTCC module, or the seconds clock output.
The RTSECSEL<1:0> (PADCFG1<2:1>) bits select
between these two outputs:
• Alarm Pulse – RTSECSEL<1:0> = 00
• Seconds Clock – RTSECSEL<1:0> = 01
 2010 Microchip Technology Inc.
DS39933D-page 169