Rainbow Electronics DS12887 User Manual
Rainbow Electronics Computer hardware
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073102
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FEATURES
§ Drop-in replacement for IBM AT computer
clock/calendar
§ Pin-compatible with the MC146818B and
DS1287
§ 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
PIN DESCRIPTION
AD0–AD7
– Multiplexed Address/Data Bus
N.C.
– No Connection
MOT
– Bus Type Selection
CS
– Chip Select
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 Supply
GND –
Ground
ORDERING INFORMATION
PART
PIN-PACKAGE
TOP MARK
TEMP RANGE
DS12887
24 PDIP Module
DS12887
0°C to +70°C
NC
DS12887
Real-Time Clock
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