DS1339 I2C Serial Real-Time Clock
Table 2. Alarm Mask Bits
ALARM 1 REGISTER MASK BITS
(Bit 7)
ALARM RATE
DY/DT
A1M4
A1M3
A1M2
A1M1
X
X
X
X
1
1
1
1
1
1
1
0
1
1
0
0
1
0
0
0
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
0
1
0
0
0
0
0
0
0
0
Alarm when day, hours, minutes, and seconds match
ALARM 2 REGISTER MASK BITS
(Bit 7)
ALARM RATE
DY/DT
A2M4
A2M3
A2M2
X
X
X
0
1
1
1
0
0
1
1
0
0
0
1
0
0
0
0
Alarm once per minute (00 sec. of every min.)
Alarm when minutes match
Alarm when hours and minutes match
Alarm when date, hours, and minutes match
Alarm when day, hours, and minutes match
1
SPECIAL-PURPOSE REGISTERS
The DS1339 has two additional registers (control and status) that control the RTC, alarms, and square-wave
output.
CONTROL REGISTER (0Eh)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
BBSQI
RS2
RS1
INTCN
A2IE
A1IE
EOSC
Bit 7: Enable Oscillator (EOSC). This bit when set to logic 0 starts the oscillator. When this bit is set to a logic 1,
the oscillator is stopped. This bit is enabled (logic 0) when power is first applied.
Bit 5: Battery-Backed Square-Wave and Interrupt Enable (BBSQI). This bit when set to a logic 1 enables the
square wave or interrupt output when VCC is absent and the DS1339 is being powered by the VBACKUP pin. When
BBSQI is a logic 0, the SQW/INT pin goes high impedance when VCC falls below the power-fail trip point. This bit is
disabled (logic 0) when power is first applied.
Bits 4 and 3: Rate Select (RS2 and RS1). These bits control the frequency of the square-wave output when the
square wave has been enabled. The table below shows the square-wave frequencies that can be selected with the
RS bits. These bits are both set to logic 1 (32kHz) when power is first applied.
Square-Wave Output Frequency
SQUARE-WAVE
RS2
RS1
OUTPUT
FREQUENCY
1Hz
0
0
1
1
0
1
0
1
4.096kHz
8.192kHz
32.768kHz
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DALLAS [ DALLAS SEMICONDUCTOR ]
