DS1287A
Real Time Clock
DS1287A
022798 1/1
FEATURES
·
Drop-in replacement for IBM AT computer clock/ca-
lendar
·
Pin compatible with the MC146818A
·
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, day of the week,
date, month, and year with leap year compensation
·
Binary or BCD representation of time, calendar, and
alarm
·
12- 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 64 RAM locations
14 bytes of clock and control registers
50 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 122
m
s to 500 ms
End of clock update cycle
PIN ASSIGNMENT
24 PIN ENCAPSULATED PACKAGE
V
CC
SQW
NC
RCLR
NC
IRQ
RESET
DS
NC
R/W
AS
CS
MOT
NC
NC
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
PIN DESCRIPTION
AD0AD7
-
Multiplexed address/data bus
NC
-
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 (open
drain)
SQW
-
Square wave output
V
CC
-
+5 volt supply
GND
-
Ground
RCLR
-
RAM clear
DESCRIPTION
The DS1287A is identical to the DS1287 with the addi-
tion of the RAM clear pin. For a complete description of
operating conditions, electrical and mechanical charac-
teristics, bus timing, and pin descriptions see the
DS12887A data sheet.
PDF 
ZIP