![](http://datasheet.mmic.net.cn/Maxim-Integrated-Products/DS3232SN-T-R_datasheet_101014/DS3232SN-T-R_11.png)
event, it is possible that the microcontroller and DS3232
I2C communications could become unsynchronized,
e.g., the microcontroller resets while reading data from
the DS3232. When the microcontroller resets, the
DS3232 I2C interface may be placed into a known state
by toggling SCL until SDA is observed to be at a high
level. At that point the microcontroller should pull SDA
low while SCL is high, generating a START condition.
If SCL is held low for greater than tIF, the internal I2C
interface is reset. This limits the minimum frequency at
which the I2C interface can be operated. If data is
being written to the device when the interface timeout is
exceeded, prior to the acknowledge, the incomplete
byte of data is not written.
Clock and Calendar
The time and calendar information is obtained by read-
ing the appropriate register bytes. Figure 1 illustrates
the RTC registers. The time and calendar data are set
or initialized by writing the appropriate register bytes.
The contents of the time and calendar registers are in
binary-coded decimal (BCD) format. The DS3232 can
be run in either 12-hour or 24-hour mode. Bit 6 of the
Extremely Accurate I2C RTC with
Integrated Crystal and SRAM
Figure 1. Address Map for DS3232 Timekeeping Registers and SRAM
Note: Unless otherwise specified, the registers’ state is not defined when power is first applied.
ADDRESS
BIT 7
MSB
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LSB
FUNCTION
RANGE
00h
0
10 Seconds
Seconds
00–59
01h
0
10 Minutes
Minutes
00–59
AM/PM
02h
0
12/24
20 Hour
10 Hour
Hour
Hours
1–12 + AM/PM
00–23
03h
0
Day
1–7
04h
0
10 Date
Date
1–31
05h
Century
0
10 Month
Month
Month/
Century
01–12 +
Century
06h
10 Year
Year
00–99
07h
A1M1
10 Seconds
Seconds
Alarm 1 Seconds
00–59
08h
A1M2
10 Minutes
Minutes
Alarm 1 Minutes
00–59
AM/PM
09h
A1M3
12/24
20 Hour
10 Hour
Hour
Alarm 1 Hours
1–12 + AM/PM
00–23
Day
Alarm 1 Day
1–7
0Ah
A1M4
DY/DT
10 Date
Date
Alarm 1 Date
1–31
0Bh
A2M2
10 Minutes
Minutes
Alarm 2 Minutes
00–59
AM/PM
0Ch
A2M3
12/24
20 Hour
10 Hour
Hour
Alarm 2 Hours
1–12 + AM/PM
00–23
Day
Alarm 2 Day
1–7
0Dh
A2M4
DY/DT
10 Date
Date
Alarm 2 Date
1–31
0Eh
EOSC
BBSQW
CONV
RS2
RS1
INTCN
A2IE
A1IE
Control
—
0Fh
OSF
BB32kHzCRATE1
CRATE0
EN32kHz
BSY
A2F
A1F
Control/Status
—
10h
SIGN
DATA
Aging Offset
—
11h
SIGN
DATA
MSB of Temp
—
12h
DATA
0
LSB of Temp
—
13h
0
Not used
Reserved for
test
14h–0FFh
x
SRAM
00h–0FFh
DS3232
Maxim Integrated
11