Microchip Technology DM183037 Data Sheet

DS30575A-page 314

 2012 Microchip Technology Inc.

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.

17.3.2

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

The RTCC pin can also 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> bits (RTCCON2<1:0>) select
between these two outputs:
• Alarm pulse – RTSECSEL<1:0> = 00
• Seconds clock – RTSECSEL<1:0> = 01

Annually, except when configured for February 29.

0000 – Every half second

0001 – Every second

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