鈥?/div>
Power鈥揻ail
write protection allows for
鹵10%
V
CC
power supply tolerance
ORDERING INFORMATION
DS1643鈥揦XX
28鈥損in DIP module
鈥?20 120 ns access
鈥?50 150 ns access
DESCRIPTION
The DS1643 is an 8K x 8 nonvolatile static RAM with a
full function real time clock which are both accessible in
a bytewide format. The nonvolatile time keeping RAM is
pin and function equivalent to any JEDEC standard
8K x 8 SRAM. The device can also be easily substituted
in ROM, EPROM and EEPROM sockets providing read/
write nonvolatility and the addition of the real time clock
function. The real time clock information resides in the
eight uppermost RAM locations. The RTC registers
contain year, month, date, day, hours, minutes, and se-
conds data in 24 hour BCD format. Corrections for the
day of the month and leap year are made automatically.
The RTC clock registers are double buffered to avoid
access of incorrect data that can occur during clock up-
date cycles. The double buffered system also prevents
time loss as the timekeeping countdown continues un-
abated by access to time register data. The DS1643
also contains its own power鈥揻ail circuitry which dese-
lects the device when the V
CC
supply is in an out of toler-
ance condition. This feature prevents loss of data from
unpredictable system operation brought on by low V
CC
as errant access and update cycles are avoided.
ECopyright
1995 by Dallas Semiconductor Corporation.
All Rights Reserved. For important information regarding
patents and other intellectual property rights, please refer to
Dallas Semiconductor data books.
041697 1/11