DS1339A Datasheet, PDF (11/19 Pages) Maxim Integrated Products – Low-Current, I2C, Serial Real-Time Clock

DS1339A
Low-Current, I²C, Serial Real-Time Clock
Alarms
The DS1339A 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
X
X
X
X
0
1
ALARM1 REGISTER MASK BITS (BIT 7)
A1M4
A1M3
A1M2
A1M1
1
1
1
1
1
1
1
0
1
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
ALARM RATE
Alarm once per second
Alarm when seconds match
Alarm when minutes and seconds match
Alarm when hours, minutes, and seconds match
Alarm when date, hours, minutes, and seconds match
Alarm when day, hours, minutes, and seconds match
DY/DT
X
X
X
0
1
ALARM2 REGISTER MASK BITS (BIT 7)
A2M4
A2M3
A2M2
1
1
1
1
1
0
1
0
0
0
0
0
0
0
0
ALARM RATE
Alarm once per minute (00 sec. of every minute)
Alarm when minutes match
Alarm when hours and minutes match
Alarm when date, hours, and minutes match
Alarm when day, hours, and minutes match
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