DS1556_10 Datasheet, PDF (6/18 Pages) Maxim Integrated Products – 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM

DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM
CLOCK OPERATIONS
Table 2 and the following paragraphs describe the operation of RTC, alarm, and watchdog functions.
Table 2. Register Map
ADDRESS
1FFFFh
1FFFEh
1FFFDh
1FFFCh
1FFFBh
1FFFAh
1FFF9h
1FFF8h
1FFF7h
1FFF6h
1FFF5h
1FFF4h
1FFF3h
1FFF2h
1FFF1h
1FFF0h
B₇
X
X
X
X
X
OSC
W
WDS
AE
AM4
AM3
AM2
AM1
Y
WF
DATA
B₆
B₅
B₄
B₃
10 Year
X
X
10
Month
X
10 Date
B₂
B₁
B₀
Year
Month
Date
Ft
X
X
X
Day
X
10 Hour
Hour
10 Minutes
Minutes
10 Seconds
Seconds
R
10 Century
Century
BMB4 BMB3 BMB2 BMB1 BMB0 RB1 RB0
Y
ABE
Y
Y
Y
Y
Y
Y
10 Date
Date
Y
10 Hours
Hours
10 Minutes
Minutes
10 Seconds
Seconds
Y
Y
Y
Y
Y
Y
Y
AF
0
BLF
0
0
0
0
FUNCTION
Year
Month
Date
Day
Hour
Minutes
Seconds
Control
Watchdog
Interrupts
Alarm Date
Alarm Hours
Alarm Minutes
Alarm Seconds
Unused
Flags
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
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
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
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 Maxim with the clock oscillator turned off, OSC bit set to a 1.
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