DS1556 1M, Nonvolatile, Y2K-Compliant Timekeeping RAM
PIN DESCRIPTION
A0–A16
DQ0–DQ7
IRQ/FT
RST
CE
OE
- Address Input
- Data Input/Outputs
- Interrupt, Frequency Test Output (Open Drain)
- Power-On Reset Output (Open Drain)
- Chip Enable
- Output Enable
- Write Enable
WE
VCC
- Power Supply Input
- Ground
GND
N.C.
- No Connection
X1, X2
- Crystal Connection
VBAT
- Battery Connection
ORDERING INFORMATION
OPERATING
VOLTAGE
(V)
PART
TEMP RANGE
PIN-PACKAGE
TOP MARK
DS1556-70
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
5
5
32 EDIP (0.740a)
32 EDIP (0.740a)
34 PowerCap
DS1556-070
DS1556-70IND
DS1556P-70
DS1556-070 IND
DS1556P-070
5
DS1556P-70IND
DS1556W-120
5
34 PowerCap
DS1556P-070 IND
DS1556W-120
3.3
3.3
3.3
3.3
32 EDIP (0.740a)
32 EDIP (0.740a)
34 PowerCap
DS1556W-120IND
DS1556WP-120
DS1556WP-120IND
DS1556W-120 IND
DS1556WP-120
DS1556WP-120 IND
34 PowerCap
DESCRIPTION
The DS1556 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) with an
RTC alarm, watchdog timer, power-on reset, battery monitor, and 128k x 8 nonvolatile static RAM. User
access to all registers within the DS1556 is accomplished with a byte-wide interface as shown in Figure 1.
The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour
BCD format. Corrections for day of month and leap year are made automatically.
The RTC registers are double-buffered into an internal and external set. The user has direct access to the
external set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow
the user to access static data. Assuming the internal oscillator is turned on, the internal set of registers is
continuously updated, which occurs regardless of external registers settings to guarantee that accurate
RTC information is always maintained.
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DALLAS [ DALLAS SEMICONDUCTOR ]
