DS1305
RTC REGISTERS
Figure 3
RTC Registers DS1305
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
SEC
10 MIN
MIN
12/2
10
10 HR
HOURS
4
P/A
0
0
0
DAY
0
10 DATE
DATE
0
10 MONTH
MONTH
10 YEAR
YEAR
Alarm 0
10 SEC ALARM
SEC ALARM
10 MIN ALARM
MIN ALARM
12/2
10
10 HR
HOUR ALARM
4
P/A
0
0
0
DAY ALARM
Alarm 1
10 SEC ALARM
SEC ALARM
10 MIN ALARM
MIN ALARM
12/2
10
10 HR
HOUR ALARM
4
P/A
0
0
0
DAY ALARM
CONTROL REGISTER
STATUS REGISTER
TRICKLE CHARGER REGISTER
RESERVED
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
Range For Alarm Registers Does Not Include Mask’m’ Bits.
The DS1305 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 (20-23
hours).
The DS1305 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 8Bh to 8Eh. The alarms can be
programmed (by the INTCN bit of the Control Register) to operate in two different modes - each alarm
can drive its own separate interrupt output or both alarms can drive a common interrupt output. 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 will only occur 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 will be generated every day
when bit 7 of the day alarm register is set to a logic 1. An alarm will be generated every hour when bit 7
of the day and hour alarm registers is set to a logic 1. Similarly, an alarm will be generated every minute
when bit 7 of the day, hour and minute alarm registers is set to a logic 1. When bit 7 of the day, hour,
minute and seconds alarm registers is set to a logic 1, alarm will occur every second.
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DALLAS [ DALLAS SEMICONDUCTOR ]
