DS1305
Figure 2. RTC REGISTERS AND ADDRESS MAP
HEX ADDRESS
READ
WRITE
00H
80H
01H
81H
02H
03H
04H
05H
06H
—
Bit7
0
0
0
0
0
0
M
M
M
M
M
M
M
M
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
RANGE
00–59
00–59
01–12 + P/A
00–23
1–7
1–31
01–12
00–99
—
82H
83H
84H
85H
86H
—
07H
08H
09H
0AH
—
87H
88H
89H
8AH
—
0BH
0CH
0DH
0EH
0FH
10H
11H
12–1FH
20–7FH
8BH
8CH
8DH
8EH
8FH
90H
91H
92–9FH
A0–FFH
10 Seconds
Seconds
10 Minutes
Minutes
P
12
10 Hour
Hours
A
24
10
0
0
0
Day
0
10 Date
Date
0
10 Month
Month
10 Year
Year
Alarm 0
10 Seconds Alarm
Seconds Alarm
10 Minutes Alarm
Minutes Alarm
P
12
10 Hour
Hour Alarm
A
24
10
0
0
0
Day Alarm
Alarm 1
10 Seconds Alarm
Seconds Alarm
10 Minutes Alarm
Minutes Alarm
P
12
10 Hour
Hour Alarm
A
24
10
0
0
0
Day Alarm
Control Register
Status Register
Trickle Charger Register
Reserved
96 Bytes User RAM
00–59
00–59
01–12 + P/A
00–23
01–07
—
00–59
00–59
01–12 + P/A
00–23
01–07
—
—
—
—
00–FF
Note:
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 to 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 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 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 occurs every second.
6 of 21
DALLAS [ DALLAS SEMICONDUCTOR ]
