DS1305 Datasheet, PDF (6/22 Pages) Dallas Semiconductor – Serial Alarm Real Time Clock RTC

DS1305
READING FROM THE CLOCK REGISTERS
Buffers are used to copy the time and date register at the beginning of a read. When reading in burst
mode, the user copy is static while the internal registers continue to increment.
Figure 2. RTC REGISTERS AND ADDRESS MAP
HEX ADDRESS
READ
WRITE
Bit7 Bit6
Bit5
Bit4 Bit3 Bit2 Bit1 Bit0
00h
80h
0
10 Seconds
Seconds
01h
81h
0
10 Minutes
Minutes
02h
82h
0 ¹²
P
A 10 Hour
Hours
24 10
03h
83h
00
0
0
Day
04h
84h
00
10 Date
Date
05h
85h
00
10 Month
Month
06h
86h
10 Year
Year
—
—
Alarm 0
07h
87h
M
10 Seconds Alarm
Seconds Alarm
08h
88h
M
10 Minutes Alarm
Minutes Alarm
09h
89h
M ¹²
P
A 10 Hour
Hour Alarm
24 10
0Ah
8Ah
M0
0
0
Day Alarm
—
—
Alarm 1
0Bh
8Bh
M
10 Seconds Alarm
Seconds Alarm
0Ch
8Ch
M
10 Minutes Alarm
Minutes Alarm
0Dh
8Dh
M ¹²
P
A 10 Hour
Hour Alarm
24 10
0Eh
8Eh
M0
0
0
Day Alarm
0Fh
8Fh
Control Register
10h
90h
Status Register
11h
91h
Trickle Charger Register
12h–1Fh 92h–9Fh
Reserved
20h–7Fh A0h–FFh
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
1–7
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
—
—
—
—
00–FF
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 2). 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,
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