bq3287/bq3287A
(
)
Real-Time Clock RTC Module
➤ Calendar in day of the week, day
of the month, months, and years
with automatic leap-year adjust-
ment
bq3287A version is identical to the
bq3287, with the addition of the RAM
clear input.
Features
➤ Dir ect clock/ca len da r r epla ce-
m en t for IBM® AT-com pa t ible
computers and other applications
The bq3287 is a fully compatible
r e a l-t im e clock for I B M AT-
compatible computers and other ap-
p lica t ion s . T h e b q 3 2 8 7 w r it e -
pr ot ect s t h e clock, ca len da r, a n d
storage registers during power fail-
u r e. Th e in t egr a l ba cku p en er gy
source then maintains data and op-
erates the clock and calendar.
➤ Programmable square wave out-
➤ Functionally compatible with the
put
DS1287/DS1287A and MC146818A
➤ Three individually maskable in-
➤ 114 bytes of general nonvolatile
terrupt event flags:
storage
- Periodic rates from 122 µs to
➤ Integral lithium cell and crystal
500 ms
➤ 160 ns cycle time allows fast bus
As shipped from Benchma rq, the
real time clock is turned off to maxi-
mize battery capacity for in-system
operation.
- Time-of-day alarm once per
operation
second to once per day
➤ Selectable Intel or Motorola bus
timing
- End-of-clock update cycle
➤ B e t t e r t h a n on e m in u t e p e r
➤ 14 bytes for clock/calendar and
The bq3287 is functionally equiva-
lent to the bq3285, except that the
battery (16, 20) and crystal (2, 3)
pins 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
retention and clock operation in the
absence of power. For a complete de-
scription of features, operating con-
dit ion s, elect r ica l ch a r a ct er ist ics,
bus timing, and pin descriptions, see
the bq3285 data sheet.
control
month clock accuracy
➤ BCD or binary format for clock
and calendar data
General Description
➤ Time of day in seconds, minutes,
Th e CMOS bq3287/bq3287A is a
low-power microprocessor periph-
eral providing a time-of-day clock
and 100-year calendar with alarm
fea t u r es a n d ba t t er y oper a t ion .
O t h e r fe a t u r e s in clu d e t h r e e
maskable interrupt sources, square-
wave output, and 114 bytes of gen-
e r a l n on vola t ile s t or a ge. Th e
and hours
- 12- or 24-hour format
- Optional daylight saving
adjustment
Pin Connections
Pin Names
AD0–AD7 Multiplexed address/data
RST
SQW
NC
Reset input
input/output
MOT
24
1
V
CC
Square wave output
No connect
MOT
CS
Bus type select input
Chip select input
NC
NC
23
22
2
3
SQW
NC
4
NC/RCL
NC
AD
AD
AD
AD
AD
AD
AD
21
20
19
18
17
16
15
14
13
0
1
2
3
4
5
6
5
RCL
RAM clear input
(bq3287A only)
AS
Address strobe input
Data strobe input
6
INT
7
RST
DS
NC
DS
8
9
VCC
VSS
+5V supply
Ground
R/W
INT
Read/write input
10
11
12
R/W
AS
CS
AD
7
Interrupt request output
V
SS
24-Pin DIP Module
PN328701.eps
Sept. 1996 D
1