BQ4285E Datasheet, PDF (1/32 Pages) Texas Instruments – Enhanced RTC With NVRAM Control

bq4285E/L
Enhanced RTC With NVRAM Control
Features
® Direct clock/calendar replace-
ment for IBM^® AT-compatible
computers and other applications
® 114 bytes of general nonvolatile
storage
® Enhanced features include:
- System wake-up capability—
alarm interrupt output active
in battery-backup mode
- 2.7–3.6V operation (bq4285L);
4.5–5.5V operation (bq4285E)
- 32kHz output for power
management
® Automatic backup and write-
protect control to external SRAM
® Functionally compatible with the
DS1285
® Less than 0.5 µA load under bat-
tery operation
® 14 bytes for clock/calendar and
control
Pin Connections
VOUT 1
X1 2
X2 3
AD0 4
AD1 5
AD2 6
AD3 7
AD4 8
AD5 9
AD6 10
AD7 11
VSS 12
24 VCC
23 SQW
22 CEOUT
21 CEIN
20 BC
19 INT
18 RST
17 DS
16 VSS
15 R/W
14 AS
13 CS
24-Pin DIP or SOIC
PN428501.eps
SLUS006A - MAY 1994 - REVISED MAY 2004
® BCD or binary format for clock
and calendar data
® Calendar in day of the week, day
of the month, months, and years,
with automatic leap-year adjust-
ment
® Time of day in seconds, minutes,
and hours
- 12- or 24-hour format
- Optional daylight saving
adjustment
® 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
® 24-pin plastic DIP or SOIC
General Description
The CMOS bq4285E/L is a low-power
microprocessor peripheral providing a
time-of-day clock and 100-year calen-
dar with alarm features and battery
operation. Other features include
three maskable interrupt sources,
square wave output, and 114 bytes of
general nonvolatile storage.
A 32.768kHz output is available for
sustaining power-management activi-
ties. Wake-up capability is provided by
an alarm interrupt, which is active in
battery-backup mode.
The bq4285E/L write-protects the
clock, calendar, and storage registers
during power failure. A backup bat-
tery then maintains data and oper-
ates the clock and calendar.
The bq4285E/L is a fully compatible
real-time clock for IBM AT-
compatible computers and other ap-
plications. The only external compo-
nents are a 32.768kHz crystal and a
backup battery.
The bq4285E/L integrates a
battery-backup controller to make a
28-Pin PLCC: No Longer Available
Pin Names
AD0–AD7 Multiplexed address/data
input/output
MOT
Bus type select input
CS
AS
DS
R/W
INT
RST
SQW
BC
X1–X2
NC
CEIN
CEOUT
VOUT
VCC
Chip select input
Address strobe input
Data strobe input
Read/write input
Interrupt request output
Reset input
Square wave output
3V backup cell input
Crystal inputs
No connect
RAM chip enable input
RAM chip enable output
Supply output
+5V supply
1