DS1285/DS1285Q
DS1285/DS1285Q
Real Time Clock
FEATURES
PIN ASSIGNMENT
MOT
X1
X2
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
V
BAT
IRQ
RESET
DS
GND
R/W
AS
CS
•
Drop-in replacement for IBM AT computer clock/ca-
lendar
•
Pin configuration closely matches MC146818A
•
Counts
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
DS1285 24–PIN DIP
VCC
SQW
MOT
NC
NC
X2
4
AD0
AD1
AD2
AD3
AD4
AD5
NC
5
6
7
8
9
10
X1
3 2
1 28 27 26
25
24
23
22
21
20
RCLR
V
BAT
IRQ
RESET
DS
GND
R/W
•
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
µs
to 500 ms
– End of clock update cycle
19
11
12 13 14 15 16 17 18
AD6
AD7
GND
NC
NC
CS
AS
DS1285Q 28-PIN PLCC
•
Optional 28-pin PLCC surface mount package
DESCRIPTION
The DS1285 Real Time Chip is a direct replacement for
the MC146818A in IBM AT computer clock/calendar
and other applications. For a complete description of
operating conditions, electrical and mechanical charac-
teristics, bus timing, and pin descriptions see the
DS12885 data sheet.
PIN DESCRIPTION
AD0-AD7
NC
MOT
CS
AS
R/W
DS
RESET
IRQ
SQW
V
CC
GND
X1,X2
V
BAT
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 drain)
Square Wave Output
+5 Volt Supply
Ground
32.768 KHz Crystal Connections
+3 Volt Battery Input
RAM Clear
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