System wake-up capability鈥?/div>
a l a r m in t e r r up t act i v e
battery-backup mode
廬
Integral lithium cell and crystal
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160 ns cycle time allows fast bus
operation
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14 bytes for clock/calendar and
control
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Time of day in seconds, minutes,
and hours
in
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Calendar in day of the week, day
of the month, months, and years
with automatic leap-year adjust-
ment
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Programmable square wave out-
put
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Three individually maskable in-
terrupt event flags:
vided by an alarm interrupt, which is
active in battery-backup mode. The
bq3287EA version is identical to the
bq3287E, with the addition of the
RAM clear input.
The bq3287E is a fully compatible
real-time clock for IBM AT-compatible
computers and other applications. The
bq3287E write-protects the clock, cal-
endar, and storage registers during
power failure. The integral backup en-
ergy source then maintains data and
operates the clock and calendar.
As shipped from Benchmarq, the
real time clock is turned off to maxi-
mize battery capacity for in-system
operation.
The bq3287E is functionally equiva-
lent to the bq3285E, except the bat-
tery (16,20) and crystal pins (2,3)
are not accessible. These pins are
connected internally to a coin cell
and quartz crystal. The coin cell is
sized to provide 10 years of data re-
tention and clock operation in the
absence of power. For a complete de-
scription of features, operating con-
ditions, electrical characteristics,
bus timing, and pin descriptions, see
the bq3285E data sheet.
-
-
-
Periodic rates from 122碌s to
500ms
Time-of-day alarm once per
second to once per day
End-of-clock update cycle
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Better than one minute per
month clock accuracy
General Description
The CMOS bq3287E/bq3287EA is a
low-power microprocessor periph-
eral providing a time-of-day clock
and 100-year calendar with alarm
features and battery operation.
Ot he r fe ature s i ncl ude t hree
maskable interrupt sources, square-
wave output, and 242 bytes of gen-
e ral no nv o l at ile s t o rag e. A
32.768kHz output is available for
sustaining power-management ac-
tivities. Wake-up capability is pro-
-
-
12- or 24-hour format
Optional daylight saving
adjustment
Pin Connections
MOT
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VCC
SQW
EXTRAM
NC/RCL
NC
INT
RST
DS
NC
R/W
AS
CS
Pin Names
AD0鈥揂D7 Multiplex address/data
input/output
MOT
CS
AS
DS
R/W
INT
Chip select input
Address strobe input
Data strobe input
Read/write input
Interrupt request output
RST
SQW
Reset input
Square wave output
EXTRAM Extended RAM enable
NC
RCL
No connect
RAM clear input
(bq3287EA only)
+5V supply
Ground
V
CC
V
SS
24-Pin DIP Module
PN3287E1.eps
Sept. 1996 C
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2
3
4
5
6
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