DS1556P Maxim Integrated Products, Inc., DS1556P Datasheet - Page 6

• Manufacturer Part Number: DS1556P
• Description: 1m, Nonvolatile, Y2k-compliant Timekeeping Ram
• Manufacturer: Maxim Integrated Products, Inc.

CLOCK OPERATIONS
Table 2 and the following paragraphs describe the operation of RTC, alarm, and watchdog functions.
Table 2. Register Map
CLOCK OSCILLATOR CONTROL
The clock oscillator can be stopped at any time. To increase the shelf life of the backup lithium battery
source, the oscillator can be turned off to minimize current drain from the battery. The OSC bit is the
MSB of the Seconds Register (B7 of 1FFF9h). Setting it to a 1 stops the oscillator, setting to a 0 starts the
oscillator. The DS1556 is shipped from Dallas Semiconductor with the clock oscillator turned off, OSC
bit set to a 1.
X = Unused, Read/Writable Under Write and Read Bit Control
Y = Unused, Read/Writable Without Write and Read Bit Control
FT = Frequency Test Bit
OSC = Oscillator Start/Stop Bit
W = Write Bit
R = Read Bit
WDS = Watchdog Steering Bit
BMB0 to BMB4 = Watchdog Multiplier Bits
ADDRESS
1FFFDh
1FFFAh
1FFFFh
1FFFEh
1FFFCh
1FFFBh
1FFF9h
1FFF8h
1FFF7h
1FFF6h
1FFF5h
1FFF4h
1FFF3h
1FFF2h
1FFF1h
1FFF0h
WDS
AM4
AM3
AM2
AM1
OSC
WF
AE
B
W
X
X
X
X
X
Y
7
BMB4
AF
B
Ft
X
X
X
Y
R
Y
Y
Y
6
10 Year
10 Seconds
10 Seconds
10 Minutes
10 Minutes
BMB3
ABE
B
X
X
Y
0
5
10 Century
10 Hours
10 Hour
10 Date
10 Date
BMB2
Month
BLF
B
10
X
Y
Y
DATA
4
BMB1
B
X
Y
Y
0
3
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DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM
AE = Alarm Flag Enable
ABE = Alarm in Battery-Backup Mode Enable
AM1 to AM4 = Alarm Mask Bits
WF = Watchdog Flag
AF = Alarm Flag
0 = 0 (Read Only)
BLF = Battery Low Flag
RB0 to RB1 = Watchdog Resolution Bits
BMB0
B
Y
Y
Seconds
Seconds
0
Minutes
Century
Minutes
Month
2
Hours
Hour
Year
Date
Date
Day
RB1
B
Y
Y
0
1
RB0
B
Y
Y
0
0
Alarm Seconds
Alarm Minutes
FUNCTION
Alarm Hours
Alarm Date
Watchdog
Interrupts
Minutes
Seconds
Control
Unused
Month
Flags
Hour
Year
Date
Day
RANGE
00-99
01-12
01-31
01-07
00-23
00-59
00-59
00-39
01-31
00-23
00-59
00-59