DS1306_05 Datasheet, PDF (6/21 Pages) Dallas Semiconductor – Serial Alarm Real-Time Clock

DS1306
Figure 2. RTC REGISTERS AND ADDRESS MAP
HEX ADDRESS
READ WRITE
Bit
7
Bit6
Bit5
Bit4
Bit3
00H
80H 0
10 SEC
01H
81H 0
10 MIN
P
12
02H
82H 0
A 10-HR
24 10
03H
83H 0 0 0
0
0
04H
84H 0 0
10-DATE
05H
85H 0 0 10-MONTH
06H
86H
10-YEAR
07H
87H M 10-SEC ALARM 0
08H
88H M 10-MIN ALARM 0
P
12
09H
89H M
A 10-HR
24 10
Bit2 Bit1
Bit0
SEC
MIN
HOURS
DAY
DATE
MONTH
YEAR
SEC ALARM 0
MIN ALARM 0
HOUR ALARM 0
0AH
8AH M 0 0
0
0
DAY ALARM 0
0BH
8BH M
0CH
8CH M
0DH
8DH M
0EH
8EH M
0FH
10H
11H
12–1FH
20–7FH
8FH
90H
91H
92–9FH
A0–
FFH
10 SEC ALARM 1
SEC ALARM 1
10 MIN ALARM 1
MIN ALARM 1
P
12
A 10-HR
HOUR ALARM 1
24 10
00
0
0
DAY ALARM 1
—
CONTROL REGISTER
STATUS REGISTER
TRICKLE CHARGER REGISTER
RESERVED
96-BYTES USER RAM
Note: Range for alarm registers does not include mask’m’ bits.
RANGE
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
—
—
—
—
—
The DS1306 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the
12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is
the AM/PM bit with logic high being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20 to 23
hours).
The DS1306 contains two time-of-day alarms. Time-of-day alarm 0 can be set by writing to registers 87h
to 8Ah. Time-of-day Alarm 1 can be set by writing to registers 8 Bh to 8 Eh. Bit 7 of each of the time-of-
day alarm registers are mask bits (Table 1). When all of the mask bits are logic 0, a time-of-day alarm
only occurs once per week when the values stored in timekeeping registers 00h to 03h match the values
stored in the time-of-day alarm registers. An alarm is generated every day when bit 7 of the day alarm
register is set to a logic 1. An alarm is generated every hour when bit 7 of the day and hour alarm
registers is set to a logic 1. Similarly, an alarm is generated every minute when bit 7 of the day, hour, and
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