DS1338_11 Datasheet, PDF (10/16 Pages) Maxim Integrated Products – I2C RTC with 56-Byte NV RAM

DS1338 I²C RTC with 56-Byte NV RAM
whenever the seconds register is written. Write transfers occur on the acknowledge from the DS1338. Once the
countdown chain is reset, to avoid rollover issues the remaining time and date registers must be written within
1 second. The 1Hz square-wave output, if enabled, transitions high 500ms after the seconds data transfer,
provided the oscillator is already running.
The DS1338 runs in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12-hour 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 20-hour bit (20–23 hours). If the 12/24-hour mode select is
changed, the hours register must be re-initialized to the new format.
On an I²C START, 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 re-read the registers in
case of an update of the main registers during a read.
Table 3. RTC and RAM Address Map
ADDRESS
00H
01H
02H
03H
04H
05H
06H
07H
08H–3FH
BIT 7
CH
0
0
0
0
0
OUT
BIT 6 BIT 5 BIT 4
12/24
10 Seconds
10 Minutes
AM/PM
20 Hour
10
Hour
0
0
0
0
10 Date
0
0
10
Month
10 Year
0
OSF SQWE
BIT 3
BIT 2 BIT 1
Seconds
Minutes
BIT 0
Hour
0
Day
Date
Month
Year
0
0
RS1 RS0
FUNCTION
Seconds
Minutes
Hours
Day
Date
Month
Year
Control
RAM 56 x 8
RANGE
00–59
00–59
1–12
+AM/PM
00–23
1–7
01–31
01–12
00–99
00H–FFH
Note: Bits listed as “0” always read as a 0.
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