Datasheet

Control Register (0Eh)
ThecontrolregistercontrolstheoperationoftheSQW/INT pin and provides oscillator status.
Bit 7: Enable Oscillator (EOSC).
WhentheEOSCbitis0,theoscillatorisenabled.Whenthisbitisa1,theoscillator
isdisabled.Thisbitiscleared(0)whenpowerisfirstapplied.
Bit 5: Battery-Backed Square-Wave Interrupt (BBSQI).When setto logic1,this bitenables theSQW/INT output
functionalitywhilethepartispoweredbyV
BACKUP
.Whensettologic0,thisbitdisablestheSQW/INT output while the
partispoweredbyV
BACKUP
.
Bits 4 and 3: Rate Select (RS2 and RS1).
ThesebitscontrolthefrequencyoftheSQW/INT output when the square-
wavehasbeenenabled(INTCN=0).Table5 lists the square-wave frequencies that can be selected with the RS bits.
Bit 2: Interrupt Control (INTCN). This bit controls the relationship between the two alarms and the interrupt output pin.
WhentheINTCNbitissettologic1,amatchbetweenthetimekeepingregistersandtheAlarm1orAlarm2registers
activatetheSQW/INTpin(providedthatthealarmisenabled).WhentheINTCNbitissettologic0,asquarewaveis
outputontheSQW/INTpin.Thisbitissettologic0whenpowerisfirstapplied.
Bit 1: Alarm 2 Interrupt Enable (A2IE).Whensettoalogic1,thisbitpermitstheAlarm2Flag(A2F)bitinthestatus
registertoassertSQW/INT(whenINTCN=1).WhentheA2IEbitissettologic0orINTCNissettologic0,theA2Fbit
doesnotinitiateaninterruptsignal.TheA2IEbitisdisabled(logic0)whenpowerisfirstapplied.
Bit 0: Alarm 1 Interrupt Enable (A1IE).Whensettologic1,thisbitpermitstheAlarm1Flag(A1F)bitinthestatus
registertoassertSQW/INT(whenINTCN=1).WhentheA1IEbitissettologic0orINTCNissettologic0,theA1Fbit
doesnotinitiateaninterruptsignal.TheA1IEbitisdisabled(logic0)whenpowerisfirstapplied.
Table 5. SQW/INT Output
Bit # BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
Name
EOSC
0 BBSQI RS2 RS1 INTCN A2IE A1IE
POR 0 0 0 1 1 0 0 0
INTCN RS2 RS1
SQW/INT OUTPUT
A2IE A1IE
0 0 0 1Hz X X
0 0 1 4.096kHz X X
0 1 0 8.192kHz X X
0 1 1 32.768kHz X X
1 X X
A1F
0 1
1 X X
A2F
1 0
1 X X
A2F
+A1F
1 1
DS1339B Low-Current, I
2
C, Serial Real-Time Clock
For High-ESR Crystals
www.maximintegrated.com
MaximIntegrated │ 12