Rainbow Electronics DS1249Y_AB - Manual

E Copyright 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.
DS1249Y/AB
2048K Nonvolatile SRAM
DS1249Y/AB
021497 1/9
FEATURES
•
10 years minimum data retention in the absence of
external power
•
Data is automatically protected during power loss
•
Unlimited write cycles
•
Low–power CMOS operation
•
Read and write access times as fast as 70 ns
•
Lithium energy source is electrically disconnected to
retain freshness until power is applied for the first time
•
Full
±
10% V
CC
operating range (DS1249Y)
•
Optional
±
5% V
CC
operating range (DS1249AB)
•
Optional industrial temperature range of –40
°
C to
+85 ° C, designated IND
•
JEDEC standard 32–pin DIP package
PIN ASSIGNMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
V CC
A15
A17
WE
A13
A8
A9
A11
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
NC
A16
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
32–PIN ENCAPSULATED PACKAGE
740 MIL EXTENDED
PIN DESCRIPTION
A0 – A17 – Address Inputs
DQ0 – DQ7 – Data In/Data Out
CE – Chip Enable
WE – Write Enable
OE – Output Enable
V
CC
– Power (+5V)
GND – Ground
NC – No Connect
DESCRIPTION
The DS1249 2048K Nonvolatile SRAMs are
2,097,152–bit, fully static, nonvolatile SRAMs orga-
nized as 262,144 words by 8 bits. Each NV SRAM has a
self–contained lithium energy source and control cir-
cuitry which constantly monitors V
CC
for an out–of–tol-
erance condition. When such a condition occurs, the
lithium energy source is automatically switched on and
write protection is unconditionally enabled to prevent
data corruption. There is no limit on the number of write
cycles which can be executed and no additional support
circuitry is required for microprocessor interfacing.