F21 datasheet(269/416 Pages) MICROCHIP

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DS30010118D-page 269

PIC24FJ256GA705 FAMILY

FIGURE 21-2:

ALARM MASK SETTINGS

21.6

Power Control

The RTCC includes a power control feature that allows

the device to periodically wake-up an external device,

wait for the device to be stable before sampling wake-up

events from that device and then shut down the external

device. This can be done completely autonomously by

the RTCC, without the need to wake-up from the current

lower power mode.

To use this feature:

Enable the RTCC (RTCEN = 1).

Set the PWCEN bit (RTCCON1L<10>).

Configure the RTCC pin to drive the PWC control

signal (RTCOE = 1 and OUTSEL<2:0> = 011).

The polarity of the PWC control signal may be chosen

using the PWCPOL bit (RTCCON1L<9>). An active-

low or active-high signal may be used with the

appropriate external switch to turn on or off the power

to one or more external devices. The active-low setting

may also be used in conjunction with an open-drain

setting on the RTCC pin, in order to drive the ground

pin(s) of the external device directly (with the appropri-

ate external VDD pull-up device), without the need for

external switches. Finally, the CHIME bit should be set

to enable the PWC periodicity.

Once the RTCC and PWC are enabled and running, the

PWC logic will generate a control output and a sample

gate output. The control output is driven out on the

RTCC pin (when RTCOE = 1 and OUTSEL<2:0> = 011)

and is used to power up or down the device, as

described above.

Once the control output is asserted, the stability

window begins, in which the external device is given

enough time to power up and provide a stable output.

Once the output is stable, the RTCC provides a sample

gate during the sample window. The use of this sample

gate depends on the external device being used, but

typically, it is used to mask out one or more wake-up

signals from the external device.

Finally, both the stability and the sample windows close

after the expiration of the sample window and the

external device is powered down.

Note 1:

Annually, except when configured for February 29.

Day of

the

Week

Month

Day

Hours

Minutes

Seconds

Alarm Mask Setting

(AMASK<3:0>)

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(1)

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