DS1285 Datasheet, PDF (1/1 Pages) Dallas Semiconductor – Real Time Clock

DS1285/DS1285Q
DS1285/DS1285Q
Real Time Clock
FEATURES
• 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
– 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 µs to 500 ms
– End of clock update cycle
• 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 ASSIGNMENT
MOT 1
24
X1 2
23
X2 3
22
AD0 4
21
AD1 5
20
AD2 6
19
AD3 7
18
AD4 8
17
AD5 9
16
AD6 10
15
AD7 11
14
GND 12
13
DS1285 24–PIN DIP
V_CC
SQW
NC
RCLR
V_BAT
IRQ
RESET
DS
GND
R/W
AS
CS
4 3 2 1 28 27 26
AD0 ₅
25 ^RCLR
AD1 6
24 VBAT
AD2 7
23 IRQ
AD3 8
22 RESET
AD4 9
21 DS
AD5 ¹⁰
20 _GND
NC
11
19
12 13 14 15 16 17 18
R/W
DS1285Q 28-PIN PLCC
PIN DESCRIPTION
AD0-AD7
– 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
GND
– ^{+5 Volt Supply}
– Ground
X1,X2
– 32.768 KHz Crystal Connections
V_BAT
RCLR
– +3 Volt Battery Input
– RAM Clear
050898 1/1