DS1556
1M, Nonvolatile, Y2K-Compliant
Timekeeping RAM
www.maxim-ic.com
FEATURES
§
Integrated NV SRAM, Real-Time Clock
(RTC), Crystal, Power-Fail Control Circuit,
and Lithium Energy Source
Clock Registers are Accessed Identically to
the Static RAM; These Registers Reside in
the 16 Top RAM Locations
Century Byte Register (i.e., Y2K Compliant)
Totally Nonvolatile with Over 10 Years of
Operation in the Absence of Power
Precision Power-On Reset
Programmable Watchdog Timer and RTC
Alarm
BCD-Coded Year, Month, Date, Day, Hours,
Minutes, and seconds with Automatic Leap-
Year Compensation Valid Up to the Year
2100
Battery Voltage-Level Indicator Flag
Power-Fail Write Protection Allows for
±10%
V
CC
Power-Supply Tolerance
Lithium Energy Source is Electrically
Disconnected to Retain Freshness Until
Power is Applied for the First Time
Also Available in Industrial Temperature
Range: -40°C to +85°C
PIN CONFIGURATIONS
TOP VIEW
RST
A16
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
32
Dallas
2
Semiconductor
31
3
DS1556
30
4
29
5
28
6
27
7
26
8
25
9
24
10
23
11
22
12
21
13
14
15
16
20
19
18
17
V
CC
A15
IRQ/FT
WE
A13
A8
A9
A11
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
§
§
§
§
§
§
Encapsulated DIP
§
§
§
§
IRQ/FT
A15
A16
RST
V
CC
WE
OE
CE
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Dallas
Semiconductor
DS1556
X1
GND
®
V
BAT
X2
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
N.C.
N.C.
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
PowerCap Module Board
(Uses DS9034PCX PowerCap)
PowerCap is a registered trademark of Dallas Semiconductor.
Note:
Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here:
1 of 20
REV: 101804
DALLAS [ DALLAS SEMICONDUCTOR ]
