Features
a174 Integrated SRAM, real-time
clock, CPU supervisor, crystal,
power-fail circuit, and battery
a174 Real-Time Clock counts hun-
dredths of seconds through years
in BCD format
a174 RAM-like clock access
a174 Compatible with industry-
standard 32K x 8 SRAMs
a174 Unlimited write cycles
a174 10-year minimum data retention
and clock operation in the ab-
sence of power
a174 Automatic power-fail chip dese-
lect and write-protection
a174 Watchdog timer, power-on reset,
alarm/periodic interrupt, power-
fail and battery-low warning
a174 Software clock calibration for
greater than ±1 minute per
month accuracy
General Description
The bq4832Y RTC Module is a non-
volatile 262,144-bit SRAM organ-
ized as 32,768 words by 8 bits with
an integral real-time clock and CPU
supervisor. The CPU supervisor pro-
vides a programmable watchdog
timer and a microprocessor reset.
Other features include alarm,
power-fail, and periodic interrupts,
and a battery-low warning.
The device combines an internal
lithium battery, quartz crystal, clock
and power-fail chip, and a full
CMOS SRAM in a plastic 32-pin
DIP module. The RTC Module di-
rectly replaces industry-standard
SRAMs and also fits into many
EPROM and EEPROM sockets
without any requirement for special
write timing or limitations on the
number of write cycles.
Registers for the real-time clock,
alarm and other special functions
are located in registers 7FF0h–
7FFFh of the memory array.
The clock and alarm registers are
dual-port read/write SRAM loca-
tions that are updated once per sec-
ond by a clock control circuit from
the internal clock counters. The
dual-port registers allow clock up-
dates to occur without interrupting
normal access to the rest of the
SRAM array.
The bq4832Y also contains a power-
fail-detect circuit. The circuit dese-
lects the device whenever VCC falls
below tolerance, providing a high de-
gree of data security. The battery is
electrically isolated when shipped
from the factory to provide maxi-
mum battery capacity. The battery
remains disconnected until the first
application of VCC.
1
RTC Module With 32Kx8 NVSRAM
bq4832Y
1
PN483201.eps
32-Pin DIP Module
2
3
4
5
6
7
8
32
31
30
29
28
27
26
25
9
10
24
23
11
12
22
21
13
14
20
19
15
16
18
17
V
CC
NC
INT
WE
A
13
A
8
A
9
A
11
OE
A
10
CE
DQ
7
DQ
6
DQ
5
DQ
4
DQ
3
RST
NC
A
14
A
12
A
7
A
6
A
5
A
4
A
3
A
2
A
1
A
0
DQ
0
DQ
1
DQ
2
V
SS
Pin Names
A0–A14 Address input
CE Chip enable
RST Microprocessor reset
WE Write enable
OE Output enable
DQ0–DQ7 Data in/data out
INT Programmable interrupt
VCC +5 volts
VSS Ground
Sept. 1996 C
Pin Connections