Rainbow Electronics DS1339 - Manual (Page 7)

DS1339
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Figure 3. ALARM MASK BITS
ALARM 1 REGISTER MASK BITS
(BIT 7) DY/DT
A1M4 A1M3 A1M2 A1M1
ALARM RATE
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
ALARM 2 REGISTER MASK BITS
(BIT 7) DY/DT
A2M4 A2M3 A2M2
ALARM RATE
X 1 1 1 Alarm once per minute (00 second 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
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
EOSC
0 BBSQI RS2 RS1 INTCN A2IE A1IE
EOSC (Enable Oscillator) – 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.
BBSQI (Battery-Backed Square-Wave and Interrupt Enable) – This bit when set to a logic 1 enables
the square-wave or interrupt output when V
CC
is absent and the DS1339 is being powered by the V
BACKUP
pin. When BBSQI is a logic 0, the SQW/
INT
pin goes high impedance when V
CC
falls below the power-
fail trip point. This bit is disabled (logic 0) when power is first applied.
RS2 and RS1 (Rate Select) – These bits control the frequency of the square-wave output when the
square wave has been enabled. Figure 4 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.