DS12887A
www.maxim-ic.com
Real-Time Clock
www.maxim-ic.com
FEATURES
PIN ASSIGNMENT (Top View)
C Drop-in replacement for IBM AT computer
clock/calendar
MOT
N.C.
N.C.
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
1
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
NC
2
3
4
5
6
7
8
9
10
C Pin compatible with the MC146818B and
DS1287A
RCLR
C Totally nonvolatile with over 10 years of
operation in the absence of power
C Self-contained subsystem includes lithium,
quartz, and support circuitry
N.C.
IRQ
RESET
DS
N.C.
R/W
AS
C Counts seconds, minutes, hours, days, day of
the week, date, month, and year with leap-
year compensation valid up to 2100
C Binary or BCD representation of time,
calendar, and alarm
11
12
CS
GND
DS12887A
24 PDIP Module (700mil)
C 12-hour or 24-hour clock with AM and PM
in 12-hour mode
Package Dimension Information
http://www.maxim-ic.com/TechSupport/DallasPackInfo.htm
C Daylight Savings Time option
C Selectable between Motorola and Intel bus
timing
PIN DESCRIPTION
C Multiplex bus for pin efficiency
C Interfaced with software as 128 RAM
locations
AD0–AD7 - Multiplexed Address/Data Bus
N.C.
- No Connect
MOT
- Bus Type Selection
– 14 bytes of clock and control registers
– 114 bytes of general-purpose RAM
C Programmable square-wave output signal
C Bus-compatible interrupt signals (IRQ)
C Three interrupts are separately software-
maskable and testable
CS
AS
- RTC Chip-Select Input
- Address Strobe
R/ W
- Read/Write Input
- Data Strobe
- Reset Input
- Interrupt Request Output
- Square-Wave Output
- +5V Main Supply
DS
RESET
IRQ
– Time-of-day alarm once/second to
once/day
SQW
VCC
– Periodic rates from 122ꢀs to 500ms
– End-of-clock update cycle
RCLR
GND
- RAM Clear
C Underwriters Laboratory (UL) recognized
- Ground
ORDERING INFORMATION
PART
PIN-PACKAGE TOP MARK TEMP RANGE
DS12887A 0°C to +70°C
DS12887A 24 PDIP Module
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.
1 of 2
073102