1 of 2 073102
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.
FEATURES
§ 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 leap-
year 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 software-
maskable 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
PIN ASSIGNMENT (Top View)
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
R/
W - Read/Write Input
DS - Data Strobe
RESET - Reset Input
IRQ - Interrupt Request Output
SQW - Square-Wave Output
V
CC
- +5V Main Supply
RCLR - RAM Clear
GND - Ground
ORDERING INFORMATION
PART PIN-PACKAGE TOP MARK TEMP RANGE
DS12887A 24 PDIP Module DS12887A 0°C to +70°C
MOT
1
2
3
4
5
6
7
8
9
10
11
12
23
DS12887A
24 PDIP Module (700mil)
N.C.
AD1
AD3
AD4
AD5
AD6
AD7
GND
V
CC
SQW
NC
N.C.
IRQ
RESET
DS
N.C.
R/W
S
CS
24
22
21
20
19
18
17
16
15
14
13
N.C.
AD0
AD2
RCLR
DS12887A
Real-Time Clock
www.maxim-ic.com
www.maxim-ic.com
