DS1285Q Dallas Semiconductor, DS1285Q Datasheet

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DS1285Q

Manufacturer Part Number
DS1285Q
Description
Real Time Clock
Manufacturer
Dallas Semiconductor
Datasheet

Specifications of DS1285Q

Case
PLCC28
Dc
93+

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FEATURES
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.
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
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
Programmable square wave output signal
Bus compatible interrupt signals (IRQ)
Three interrupts are separately software-maskable
and testable
Optional 28-pin PLCC surface mount package
– 14 bytes of clock and control registers
– 50 bytes of general purpose RAM
– Time-of-day alarm once/second to once/day
– Periodic rates from 122 s to 500 ms
– End of clock update cycle
PIN ASSIGNMENT
PIN DESCRIPTION
AD0-AD7
NC
MOT
CS
AS
R/W
DS
RESET
IRQ
SQW
V
GND
X1,X2
V
RCLR
CC
BAT
AD0
AD1
AD2
AD3
AD4
AD5
NC
GND
MOT
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
X1
X2
5
6
7
8
9
10
11
– 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
– Ground
– 32.768 KHz Crystal Connections
– +3 Volt Battery Input
– RAM Clear
DS1285Q 28-PIN PLCC
12 13 14 15 16 17 18
4
DS1285 24–PIN DIP
1
2
3
4
5
6
7
8
9
10
11
12
+5 Volt Supply
DS1285/DS1285Q
3 2
Real Time Clock
1
28 27 26
24
23
22
21
20
19
18
17
16
15
14
13
25
24
23
22
21
20
19
DS1285/DS1285Q
V
SQW
NC
RCLR
V
IRQ
RESET
DS
GND
R/W
AS
CS
CC
BAT
RCLR
V
IRQ
RESET
DS
GND
R/W
BAT
050898 1/1

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