DS1306
CLOCK, CALENDAR, AND ALARM
The time and calendar information is obtained by reading the appropriate register bytes. The real time
clock registers are illustrated in Figure 3. The time, calendar, and alarm are set or initialized by writing
the appropriate register bytes. Note that some bits are set to 0. These bits will always read 0 regardless
of how they are written. Also note that registers 12h to 1Fh (read) and registers 92h to 9Fh are reserved.
These registers will always read 0 regardless of how they are written. The contents of the time, calendar,
and alarm registers are in the Binary-Coded Decimal (BCD) format.
RTC REGISTERS
Figure 3
RTC REGISTERS DS1306
HEX ADDRESS
READ WRITE
00H
80H
01H
81H
02H
82H
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
RANGE
0
0
0
0
0
0
03H
04H
05H
06H
07H
08H
09H
0AH
0BH
0CH
0DH
0EH
0FH
10H
11H
12-1FH
83H
84H
85H
86H
87H
88H
89H
8AH
8BH
8CH
8DH
8EH
8FH
90H
91H
92-9FH
M
M
M
M
M
M
M
M
10 SEC
10 MIN
12/2
10
10 HR
4
P/A
0
0
0
0
0
10 DATE
0
10 MONTH
10 YEAR
Alarm 0
10 SEC ALARM
10 MIN ALARM
12/2
10
10 HR
4
P/A
0
0
0
0
Alarm 1
10 SEC ALARM
10 MIN ALARM
12/2
10
10 HR
4
P/A
0
0
0
0
SEC
MIN
HOURS
DAY
DATE
MONTH
YEAR
SEC ALARM
MIN ALARM
HOUR ALARM
DAY ALARM
SEC ALARM
MIN ALARM
HOUR ALARM
DAY ALARM
00-59
00-59
01-12 + P/A
00-23
01-07
1-31
01-12
00-99
00-59
00-59
01-12 + P/A
00-23
01-07
00-59
00-59
01-12 + P/A
00-23
01-07
CONTROL REGISTER
STATUS REGISTER
TRICKLE CHARGER REGISTER
RESERVED
NOTE:
Range for alarm registers does not include mask’m’ bits.
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DALLAS [ DALLAS SEMICONDUCTOR ]
