DS1286 Datasheet, PDF (3/18 Pages) Dallas Semiconductor – Watchdog Timekeeper

DS1284/DS1286
PIN DESCRIPTION
PIN
DIP EDIP PLCC
1
1
1
2, 3
—
2, 3
4
5–10
11, 12,
13, 15,
16–19
14, 21
20
22
23
2, 3, 4,
21, 24,
25
5–10
11, 12,
13, 15,
16–19
14
20
22
23
4
5–10
11, 12,
13, 15,
16–19
14, 21
20
22
23
24
—
24
25
—
25
26
26
26
27
27
27
NAME
INTA
X1, X2
FUNCTION
Active-Low Interrupt Output A. This open-drain pin requires a
pullup resistor for proper operation.
Connections for Standard 32.768kHz Quartz Crystal. The internal
oscillator circuitry is designed for operation with a crystal having
a specified load capacitance (C_L) of 6pF. The crystal is connected
directly to the X1 and X2 pins. There is no need for external
capacitors or resistors. For more information on crystal selection
and crystal layout considerations, refer to Application Note 58:
Crystal Considerations with Dallas Real Time Clocks.
N.C. No Connection
A5–A0
DQ0, DQ1,
DQ2, DQ3,
DQ4–DQ7
GND
CE
OE
SQW
RCLR
V_BAT
INTB
(INTB)
WE
Address Inputs
Data Input/Output
Ground
Active-Low Chip-Enable Input
Active-Low Output-Enable Input
Square-Wave Output. Push-pull output. High impedance when
V_CC is below V_TP.
Active-Low RAM Clear. Used to clear (set to logic 1) all 50
bytes of user NV RAM, but does not affect the registers
involved with time, alarm, and watchdog functions. To clear the
RAM, RCLR must be forced to an input logic 0 (-0.3V to
+0.8V) during battery-backup mode when V_CC is not applied.
The RCLR function is designed to be used via human interface
(shorting to ground or by switch) and not be driven with external
buffers. This pin is internally pulled up and should be left
floating when not in use.
Input for Any Standard 3V Lithium Cell or Other Energy
Source. Input voltage must be held between the minimum and
maximum limits for proper operation. The supply should be
connected directly to the V_BAT pin. A diode must not be placed
in series with the battery to the V_BAT pin. Furthermore, a diode is
not necessary because reverse charging current-protection
circuitry is provided internal to the device and has passed the
requirements of Underwriters Laboratories for UL listing. This
pin should be grounded but can be left floating.
Active-Low (Active-High) Interrupt Output B. When the active-
high state is selected (IBH = 1), an open-drain pullup transistor
connected to V_CC sources current when the output is active.
When the active-low state is selected (IBH = 0), an open-drain
pulldown transistor connected to ground sinks current when the
output is active. If active-high output operation is selected, a
pulldown resistor is required for proper operation. When active-
low output operation is selected, a pullup resistor is required for
proper operation.
Active-Low Write-Enable Input
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