DS1553P Maxim Integrated Products, DS1553P Datasheet - Page 5

• Manufacturer Part Number: DS1553P
• Description: 64K NV Y2KC Real Time Clocks RAM
• Manufacturer: Maxim Integrated Products

DS1553 REGISTER MAP Table 2
CLOCK OSCILLATOR CONTROL
The Clock oscillator may 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
MSB of the Seconds Register (B7 of 1FF9h). Setting it to a 1 stops the oscillator, setting to a 0 starts the
oscillator. The DS1553 is shipped from Dallas Semiconductor with the clock oscillator turned off,
bit set to a 1.
READING THE CLOCK
When reading the RTC data, it is recommended to halt updates to the external set of double-buffered RTC
Registers. This puts the external registers into a static state allowing data to be read without register
values changing during the read process. Normal updates to the internal registers continue while in this
state. External updates are halted when a 1 is written into the read bit, B6 of the Control Register (1FF8h).
As long as a 1 remains in the Control Register read bit, updating is halted. After a halt is issued, the
registers reflect the RTC count (day, date, and time) that was current at the moment the halt command
was issued. Normal updates to the external set of registers will resume within 1 second after the read bit is
set to a 0 for a minimum of 500 s. The read bit must be a zero for a minimum of 500 s to ensure the
external registers will be updated.
ADDRESS
X = Unused, read/writable under Write and Read
FT = Frequency Test bit
W = Write bit
R = Read bit
WDS = Watchdog Steering bit
BMB0-BMB4 = Watchdog Multiplier bits
RB0-RB1 = Watchdog Resolution bits
OSC
1FFDh
1FFCh
1FFBh
1FFAh
1FFEh
1FFFh
1FF9h
1FF8h
1FF7h
1FF6h
1FF5h
1FF4h
1FF3h
1FF2h
1FF1h
1FF0h
bit control
= Oscillator start/stop bit
WDS
AM4
AM3
AM2
AM1
OSC
WF
AE
B
W
X
X
X
X
X
Y
7
BMB4
AF
FT
B
X
X
X
Y
Y
Y
Y
R
6
10 Year
10 SECONDS
10 SECONDS
10 MINUTES
10 MINUTES
BMB3
ABE
10 CENTURY
B
X
X
Y
10 HOURS
0
10 HOUR
10 DATE
5
10 Date
BMB2
10 M
BLF
B
DATA
X
Y
Y
4
BMB1
B
X
Y
Y
0
3
BLF = Battery Low Flag
AE = Alarm Flag Enable
Y = Unused, read/writable without Write and Read
ABE = Alarm in battery Back-up mode enable
AM1-AM4 = Alarm Mask bits
WF = Watchdog Flag
AF = Alarm Flag
0 = 0 and are read only
5 of 19
BMB0
CENTURY
MINUTES
SECONDS
MINUTES
SECONDS
MONTH
HOURS
B
HOUR
Y
Y
YEAR
DATE
DATE
0
2
bit control
DAY
RB1
B
Y
Y
0
1
RB0
B
Y
Y
0
0
ALARM SECONDS
ALARM MINUTES
ALARM HOURS
ALARM DATE
INTERRUPTS
WATCHDOG
FUNCTION/RANGE
CONTROL
SECONDS
MINUTES
UNUSED
MONTH
FLAGS
HOUR
YEAR
DATE
DAY
OSC
bit is the
00-99
01-12
01-31
01-07
00-23
00-59
00-59
00-39
01-31
00-23
00-59
00-59
DS1553
OSC