MCP7940N-ESLASHMS datasheet(20/58 Pages) MICROCHIP

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MCP7940N

DS20005010J-page 20

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5.4

Alarms

The MCP7940N features two independent alarms.

Each alarm can be used to either generate an interrupt

at a specific time in the future, or to generate a periodic

interrupt every minute, hour, day, day of week, or

month.

There is a separate interrupt flag, ALMxIF, for each

alarm. The interrupt flags are set by hardware when the

chosen alarm mask condition matches (Table 5-5). The

interrupt flags must be cleared in software.

If either alarm module is enabled by setting the corre-

sponding ALMxEN bit in the CONTROL register, and if

the square wave clock output is disabled (SQWEN =

0), then the MFP will operate in Alarm Interrupt Output

mode. Refer to Section 5.5 “Output Configurations”

for details. The alarm interrupt output is available while

operating from the backup power supply.

Both Alarm0 and Alarm1 offer identical operation. All

time and date values are stored in the registers as

binary-coded decimal (BCD) values.

TABLE 5-5:

ALARM MASKS

FIGURE 5-6:

ALARM BLOCK DIAGRAM

Note:

Throughout this section, references to the

ules are referred to generically by the use

of ‘x’ in place of the specific module num-

ber. Thus, “ALMxSEC” might refer to the

seconds register for Alarm0 or Alarm1.

ALMxMSK<2:0>

Alarm Asserts on Match of

000

Seconds

001

Minutes

010

Hours

011

Day of Week

100

Date

101

Reserved

110

Reserved

111

Seconds, Minutes, Hours, Day of

Week, Date, and Month

Note 1: The alarm interrupt flags must be cleared

by the user. If a flag is cleared while the

corresponding

alarm

condition

still

matches, the flag will be set again, gener-

ating another interrupt.

2: Loading invalid values into the alarm reg-

isters will result in undefined operation.

MFP

RTCSEC

RTCMIN

RTCHOUR

RTCWKDAY

RTCDATE

RTCMTH

Timekeeping

Registers

ALM1SEC

ALM1MIN

ALM1HOUR

ALM1WKDAY

ALM1DATE

ALM1MTH

Alarm1

Registers

ALM0SEC

ALM0MIN

ALM0HOUR

ALM0WKDAY

ALM0DATE

ALM0MTH

Alarm0

Registers

Alarm0 Mask

Alarm1 Mask

Comparator

MFP Output Logic

Set

ALM0IF

Set

ALM1IF

ALM0MSK<2:0>

ALM1MSK<2:0>

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