DS1284 Datasheet, PDF (1/3 Pages) Dallas Semiconductor – Watchdog Timekeeper Chip

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FEATURES
§ Keeps track of hundredths of seconds,
seconds, minutes, hours, days, date of the
month, months, and years; valid leap year
compensation up to 2100
§ Watchdog timer restarts an out-of-control
processor
§ Alarm function schedules real-time related
activities
§ Programmable interrupts and square wave
outputs maintain 28-pin JEDEC footprint
§ All registers are individually addressable via
the address and data bus
§ Accuracy is better than ±2 minute/month at
25°C
§ 50 bytes of user NV RAM
§ Optional 28-pin PLCC surface mount package
§ Low-power CMOS circuitry is maintained on
less than 0.5 µA when power is supplied from
battery input
§ Optional industrial temperature range
available on 28-pin PLCC (-40°C to +85°C)
DS1284
Watchdog Timekeeper Chip
PIN ASSIGNMENT
INTA 1
X1 ₂
X2 3
NC 4
A5 5
A4 6
A3 7
A2 8
A1 9
A0 10
DQ0 11
DQ1 12
DQ2 ¹³
GND 14
28 VCC
27 WE
26 INTB(INTB)
25 VBAT
24 RCLR
23
SQW
4 3 2 1 28 27 26
A5 ⁵
25 _VBAT
22 OE
A4 ⁶
24 _RCLR
21 GND A3 ⁷
23 _SQW
20 CE
A2 ⁸
22 _OE
19 DQ7 ^{A1 9}
21 _GND
18
DQ6
A0
DQ0
10
11
20 _CE
19 _DQ7
17 _DQ5
12 13 14 15 16 17 18
16 DQ4
15 DQ3
DS1284
28-Pin DIP (600-mil)
DS1284
28-Pin PLCC
PIN DESCRIPTION
INTA
- Interrupt Output A (open drain)
INTB (INTB) - Interrupt Output B (open drain)
A0-A5
- Address Inputs
DQ0-DQ7 - Data Input/Output
CE
- Chip Enable
OE
- Output Enable
WE
V_CC
GND
NC
SQW
X1,X2
V_BAT
RCLR
- Write Enable
- +5 Volts
- Ground
- No Connection
- Square Wave Output
- 32.768 kHz Crystal Connections
- +3 Volt Battery Input
- RAM Clear
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.
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