DS1341_12 Datasheet, PDF (9/16 Pages) Maxim Integrated Products – Low-Current I2C RTCs for High-ESR Crystals

Low-Current I²C RTCs for High-ESR Crystals
the ECLK bit is set. The external clock reference must be
within the defined frequency tolerance prior to initializing
the LOS flag.
Register Map
Table 1 shows the map for the DS1341/DS1342 regis-
ters. During a multibyte access, if the address pointer
reaches the end of the register space (0Fh), it wraps
around to location 00h. On either an I²C START or
address pointer incrementing to location 00h, the current
time is transferred to a second set of registers. The time
information is read from these secondary registers while
the clock continues to run. This eliminates the need to
reread the registers in case the main registers update
during a read.
I²C Interface
The I²C interface is guaranteed to operate when VCC is
between 1.8V and 5.5V and the EOSC bit is 0. The I²C
interface is accessible whenever VCC is at a valid level.
To prevent invalid device operation, the I²C interface
should not be accessed when VCC is below +1.8V.
If a microcontroller connected to the DS1341/DS1342
resets during I²C communications, it is possible that the
microcontroller and the DS1341/DS1342 could become
unsynchronized. When the microcontroller resets, the
DS1341/DS1342 I²C interface can be placed into a
known state by holding SCL low for tTIMEOUT. Doing so
limits the minimum frequency at which the I²C interface
can be operated. If data is being written to the device
Table 1. Register Map
ADDRESS
00h
01h
02h
03h
04h
BIT 7
0
0
0
0
0
BIT 6 BIT 5 BIT 4
10 Seconds
10 Minutes
12/24
AM/PM
10hr
10hr
0
0
0
0
10 Date
05h
CENT
0
0
10 MO
06h
10 Year
07h
A1M1
10 Seconds
BIT 3
0
BIT 2 BIT 1
Seconds
Minutes
Hour
Day
Date
Month
Year
Seconds
08h
A1M2
10 Minutes
09h
A1M3
12/24
AM/PM
10hr
10hr
0Ah
A1M4 DY/DT
10 Date
Minutes
Hour
Day,
Date
0Bh
A2M2
10 Minutes
Minutes
0Ch
A2M3
12/24
AM/PM
10hr
10hr
Hour
0Dh
A2M4 DY/DT
10 Date
Day,
Date
0Eh
EOSC
0
EGFIL RS2
RS1 INTCN A2IE
0Fh
OSF DOSF LOS CLKSEL2 CLKSEL1 ECLK A2F
Note: Bits listed as 0 always read back as 0 and cannot be written to a 1.
BIT 0
A1IE
A1F
FUNCTION
Seconds
Minutes
Hours
Day
Date
Month/
Century
Year
Alarm 1
Seconds
Alarm 1
Minutes
Alarm 1
Hours
Alarm 1 Day,
Alarm 1 Date
Alarm 2
Minutes
Alarm 2
Hours
Alarm 2 Day,
Alarm 2 Date
Control
Control/
Status
RANGE
00–59
00–59
1–12+AM/PM
00–23
1–7
01–31
01–12 + Century
00–99
00–59
00–59
1–12 + AM/PM
00–23
1–7
1–31
00–59
1–12 + AM/PM
00–23
1–7
1–31
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