DS1685/DS1687 3V/5V Real-Time Clocks
“don’t care” codes in all three time alarm bytes create an interrupt every second. The three time-alarm bytes can be
used with the date alarm as described in the Wake-Up/Kickstart section. The century counter is discussed later in
this text.
All registers can be directly written or read except for the following:
1) Registers C and D are read-only.
2) Bit 7 of Register A is read-only.
3) Bit 7 of the seconds byte is read-only.
Table 2A. Time, Calendar, and Alarm Data Modes—BCD Mode (DM = 0)
ADDRESS
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FUNCTION
RANGE
00H
0
10 Seconds
Seconds
Seconds
Seconds
Alarm
Minutes
Minutes
Alarm
00-59
01H
02H
03H
0
0
0
10 Seconds
10 Minutes
10 Minutes
Seconds
Minutes
Minutes
00-59
00-59
00-59
1-12
+AM/PM
00-23
1-12
AM/PM
0
10 Hour
10 Hour
04H
0
0
Hours
Hours
Hours
0
10 Hour
AM/PM
0
Hours
Alarm
05H
+AM/PM
00-23
01-07
01-31
01-12
00-99
0
10 Hr
06H
07H
08H
09H
0
0
0
0
0
0
0
0
0
0
Day
Day
Date
Month
Year
10 Date
Date
Month
Year
10 Month
10 Year
0AH
0BH
0CH
0DH
UIP
SET
IRQF
VRT
DV2
PIE
PF
0
DV1
AIE
AF
0
DV0
UIE
UF
0
RS3
RS2
DM
0
RS1
24/12
0
RS0
DSE
0
Control
Control
Control
Control
SQWE
0
0
0
0
0
Bank 1
Century
48H
49H
Century
00-99
01-31
Bank 1
10 Date
Date
Date Alarm
X = Read/Write Bit.
Note 1: Unless otherwise specified, the state of the registers is not defined when power is first applied.
Note 2: Except for the seconds register, 0 bits in the time and date registers can be written to a 1, but may be modified when the clock updates.
0 bits should always be written to 0 except for alarm mask bits.
10 of 39
DALLAS [ DALLAS SEMICONDUCTOR ]
