BQ3287E_14 Datasheet, PDF (1/8 Pages) Texas Instruments – Real-Time Clock (RTC) Module

Not Recommended For New Designs
bq3287E/bq3287EA
Real-Time Clock ^(RTC) Module
Features
® Direct clock/calendar replace-
ment for IBM^®AT-compatible
computers and other applications
® Functionally compatible with
the DS1287/DS1287A and
MC146818A/ MC146818B
® 242 bytes of general nonvolatile
storage
® Provides a 32.768kHz output for
power management
® System wake-up capability—
alarm interrupt active in
battery-backup mode
® Integral lithium cell and crystal
® 160 ns cycle time allows fast bus
operation
® 14 bytes for clock/calendar and
control
® Time of day in seconds, minutes,
and hours
- 12- or 24-hour format
- Optional daylight saving
adjustment
Pin Connections
MOT 1
NC 2
NC 3
AD0 4
AD1 5
AD2 6
AD3 7
AD4 8
AD5 9
AD6 10
AD7 11
VSS 12
24 VCC
23 SQW
22 EXTRAM
21 NC/RCL
20 NC
19 INT
18 RST
17 DS
16 NC
15 R/W
14 AS
13 CS
24-Pin DIP Module
PN3287E1.eps
® Calendar in day of the week, day
of the month, months, and years
with automatic leap-year adjust-
ment
® Programmable square wave out-
put
® Three individually maskable in-
terrupt event flags:
- Periodic rates from 122µs to
500ms
- Time-of-day alarm once per
second to once per day
- End-of-clock update cycle
® 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.
Other features include three
maskable interrupt sources, square-
wave output, and 242 bytes of gen-
eral nonvolatile storage. A
32.768kHz output is available for
sustaining power-management ac-
tivities. Wake-up capability is pro-
Pin Names
AD0–AD7 Multiplex address/data
input/output
MOT
CS
Chip select input
AS
Address strobe input
DS
Data strobe input
R/W
Read/write input
INT
Interrupt request output
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.
RST
Reset input
SQW
Square wave output
EXTRAM Extended RAM enable
NC
No connect
RCL
RAM clear input
(bq3287EA only)
VCC
+5V supply
VSS
Ground
Sept. 1996 C
1