ds1305et-r Maxim Integrated Products, Inc., ds1305et-r Datasheet - Page 6

• Manufacturer Part Number: ds1305et-r
• Description: Ds1305 Serial Alarm Real-time Clock
• Manufacturer: Maxim Integrated Products, Inc.

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