DS1287A
DS1287A
Real Time Clock
FEATURES
PIN ASSIGNMENT
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
V
CC
SQW
NC
RCLR
NC
IRQ
RESET
DS
NC
R/W
AS
CS
•
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
•
Counts
subsystem includes lithium, quartz,
and support circuitry
seconds, minutes, hours, day of the week,
date, month, and year with leap year compensation
alarm
•
Binary or BCD representation of time, calendar, and
•
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
24 PIN ENCAPSULATED PACKAGE
PIN DESCRIPTION
AD0–AD7
NC
MOT
CS
AS
R/W
DS
RESET
IRQ
drain)
SQW
V
CC
GND
RCLR
-
-
-
-
-
-
-
-
-
-
-
-
-
Multiplexed address/data bus
No connection
Bus type selection
Chip select
Address strobe
Read/write input
Data strobe
Reset input
Interrupt request output (open
Square wave output
+5 volt supply
Ground
RAM clear
•
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
ms
to 500 ms
– End of clock update cycle
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.
022798 1/1
DALLAS [ DALLAS SEMICONDUCTOR ]
