Datasheet

Alarms
The device contains two time of day/date alarms. Alarm 1
canbesetbywritingtoregisters07hto0Ah.Alarm2can
besetbywritingtoregisters0Bhto0Dh.Thealarmscan
beprogrammed(bytheAlarmEnableandINTCNbitsof
theControlRegister)toactivatetheSQW/INT output on
an alarm match condition. Bit 7 of each of the time of day/
date alarm registers are mask bits (Table 4
).Whenallthe
maskbitsforeachalarmarelogic0,analarmonlyoccurs
whenthevaluesinthetimekeepingregisters00hto06h
match the values stored in the time of day/date alarm
registers. The alarms can also be programmed to repeat
every second, minute, hour, day, or date. Table 4 shows
the possible settings. Configurations not listed in the table
result in illogical operation.
The DY/DT bits (bit 6 of the alarm day/date registers)
controlwhether the alarmvalue storedin bits 0to 5of
that register reflects the day of the week or the date of
themonth.IfDY/DTiswrittentoalogic0,thealarmis
theresultofamatchwithdateofthemonth.IfDY/DT is
written to a logic 1, the alarm is the result of a match with
day of the week.
The device checks for an alarm match once per second.
When the RTC register values match alarm register
settings,thecorrespondingAlarmFlag‘A1F’or‘A2F’bitis
settologic1.IfthecorrespondingAlarmInterruptEnable
‘A1IE’or‘A2IE’isalsosettologic1andtheINTCNbitis
settologic1,thealarmconditionactivatestheSQW/INT
signal.IftheBBSQIbitissetto1,theINT output activates
whilethepartisbeingpoweredbyV
BACKUP
. The alarm
output remains active until the alarm flag is cleared by
the user.
Table 4. Alarm Mask Bits
DY/DT
ALARM1 REGISTER MASK BITS (BIT 7)
ALARM RATE
A1M4 A1M3 A1M2 A1M1
X 1 1 1 1 Alarm once per second
X 1 1 1 0 Alarm when seconds match
X 1 1 0 0 Alarm when minutes and seconds match
X 1 0 0 0 Alarm when hours, minutes, and seconds match
0 0 0 0 0 Alarm when date, hours, minutes, and seconds match
1 0 0 0 0 Alarm when day, hours, minutes, and seconds match
DY/DT
ALARM2 REGISTER MASK BITS (BIT 7)
ALARM RATE
A2M4 A2M3 A2M2
X 1 1 1
Alarmonceperminute(00sec.ofeveryminute)
X 1 1 0 Alarm when minutes match
X 1 0 0 Alarm when hours and minutes match
0 0 0 0 Alarm when date, hours, and minutes match
1 0 0 0 Alarm when day, hours, and minutes match
DS1339B Low-Current, I
2
C, Serial Real-Time Clock
For High-ESR Crystals
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