Address Map
Table 2 shows the address map for the DS1390–
DS1393 RTC and RAM registers. The RTC registers are
located in address locations 00h to 0Fh in read mode,
and 80h to 8Fh in write mode. During a multibyte
access, when the address pointer reaches 0Fh, it
wraps around to location 00h. On the falling edge of the
CS pin (DS1390/DS1391) or the rising edge of CE
(DS1392/DS1393), the current time is transferred to a
second set of registers. The time information is read
from these secondary registers, while the clock may
continue to run. This eliminates the need to re-read the
registers if the main registers update during a read. To
avoid rollover issues when writing to the time and date
registers, all registers should be written before the hun-
dredths-of-seconds registers reaches 99 (BCD).
DS1390/DS1391/DS1392/DS1393
Low-Voltage SPI/3-Wire RTCs with
Trickle Charger
____________________________________________________________________ 13
Table 2. Address Map
Note: Unless otherwise specified, the state of the registers is not defined when power (V
CC
and V
BACKUP
) is first applied.
X = General-purpose read/write bit.
0 = Always reads as zero.
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