DS12887A
Real-Time Clock
www.maxim-ic.com
www.maxim-ic.com
FEATURES
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PIN ASSIGNMENT (Top View)
Drop-in replacement for IBM AT computer
clock/calendar
Pin compatible with the MC146818B and
DS1287A
Totally nonvolatile with over 10 years of
operation in the absence of power
Self-contained subsystem includes lithium,
quartz, and support circuitry
Counts seconds, minutes, hours, days, day of
the week, date, month, and year with leapyear compensation valid up to 2100
Binary or BCD representation of time,
calendar, and alarm
12-hour or 24-hour clock with AM and PM
in 12-hour mode
Daylight Savings Time option
Selectable between Motorola and Intel bus
timing
Multiplex bus for pin efficiency
Interfaced with software as 128 RAM
locations
– 14 bytes of clock and control registers
– 114 bytes of general-purpose RAM
Programmable square-wave output signal
Bus-compatible interrupt signals (IRQ)
Three interrupts are separately softwaremaskable and testable
– Time-of-day alarm once/second to
once/day
– Periodic rates from 122ms to 500ms
– End-of-clock update cycle
Underwriters Laboratory (UL) recognized
MOT
N.C.
N.C.
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
NC
RCLR
N.C.
IRQ
RESET
DS
N.C.
R/W
AS
CS
DS12887A
24 PDIP Module (700mil)
Package Dimension Information
http://www.maxim-ic.com/TechSupport/DallasPackInfo.htm
PIN DESCRIPTION
AD0–AD7 - Multiplexed Address/Data Bus
N.C.
- No Connect
MOT
- Bus Type Selection
CS
- RTC Chip-Select Input
AS
- Address Strobe
- Read/Write Input
R/ W
DS
- Data Strobe
RESET
- Reset Input
IRQ
- Interrupt Request Output
SQW
- Square-Wave Output
VCC
- +5V Main Supply
RCLR
- RAM Clear
GND
- Ground
ORDERING INFORMATION
PART
PIN-PACKAGE
DS12887A 24 PDIP Module
TOP MARK
DS12887A
TEMP RANGE
0°C to +70°C
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: http://www.maxim-ic.com/errata.
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