DS1284
Watchdog Timekeeper Chip
www.dalsemi.com
FEATURES
搂
Keeps track of hundredths of seconds,
seconds, minutes, hours, days, date of the
month, months, and years; valid leap year
compensation up to 2100
搂
Watchdog timer restarts an out-of-control
processor
搂
Alarm function schedules real-time related
activities
搂
Programmable interrupts and square wave
outputs maintain 28-pin JEDEC footprint
搂
All registers are individually addressable via
the address and data bus
搂
Accuracy is better than 卤2 minute/month at
25掳C
搂
50 bytes of user NV RAM
搂
Optional 28-pin PLCC surface mount package
搂
Low-power CMOS circuitry is maintained on
less than 0.5
碌A
when power is supplied from
battery input
搂
Optional industrial temperature range
available on 28-pin PLCC (-40掳C to +85掳C)
PIN ASSIGNMENT
INTA
X1
X2
NC
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
NC
X2
X1
INTA
VCC
WE
INTB(INTB)
4
5
6
7
8
9
10
11
12
13 14
15
16
17
18
3
2
1
28
27
26
25
24
23
22
21
20
19
V
CC
WE
INTB(INTB)
V
BAT
RCLR
SQW
A5
OE
A4
A3
GND
A2
CE
A1
DQ7
A0
DQ6 DQ0
DQ5
DQ4
DQ3
VBAT
RCLR
SQW
OE
GND
CE
DQ7
DS1284
28-Pin DIP (600-mil)
DS1284
28-Pin PLCC
PIN DESCRIPTION
- Interrupt Output A (open drain)
INTB
(INTB) - Interrupt Output B (open drain)
A0-A5
- Address Inputs
DQ0-DQ7
- Data Input/Output
- Chip Enable
CE
- Output Enable
OE
- Write Enable
WE
V
CC
- +5 Volts
GND
- Ground
NC
- No Connection
SQW
- Square Wave Output
X1,X2
- 32.768 kHz Crystal Connections
V
BAT
- +3 Volt Battery Input
- RAM Clear
RCLR
INTA
DESCRIPTION
The DS1284 Watchdog Timekeeper Chip is a self-contained real-time clock, alarm, watchdog timer, and
interval timer in a 28-pin JEDEC DIP package or a 28-pin PLCC surface mount package. An external
crystal and battery are the only components required to maintain time-of-day and memory status in the
absence of power. For a complete description of operating conditions, electrical characteristics, bus
timing, and pin descriptions other than X1, X2, V
BAT
, and
RCLR
, see the DS1286 Watchdog Timekeeper
data sheet.
1 of 3
DQ1
DQ2
GND
DQ3
DQ4
DQ5
DQ6
072799
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2
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