U634H256
PowerStore
32K x 8 nvSRAM
Features
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High-performance CMOS non-
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Description
The U634H256 has two separate
modes of operation: SRAM mode
and nonvolatile mode. In SRAM
mode, the memory operates as an
ordinary static RAM. In nonvolatile
operation, data is transferred in
parallel from SRAM to EEPROM or
from EEPROM to SRAM. In this
mode SRAM functions are disab-
led.
The U634H256 is a fast static RAM
(25, 35, 45 ns), with a nonvolatile
electrically
erasable
PROM
(EEPROM) element incorporated
in each static memory cell. The
SRAM can be read and written an
unlimited number of times, while
independent nonvolatile data resi-
des in EEPROM. Data transfers
from the SRAM to the EEPROM
(the STORE operation) take place
automatically upon power down
using charge stored in an external
100 碌F capacitor.
Transfers from the EEPROM to the
SRAM (the RECALL operation)
take place automatically on power
up.
The U634H256 combines the high
performance and ease of use of a
fast SRAM with nonvolatile data
integrity.
Pin Description
32
31
30
29
28
27
VCCX
HSB
W
A13
A8
A9
A11
G
n.c.
A10
E
DQ7
DQ6
DQ5
DQ4
DQ3
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volatile static RAM 32768 x 8 bits
25, 35 and 45 ns Access Times
10, 15 and 20 ns Output Enable
Access Times
I
CC
= 15 mA typ. at 200 ns Cycle
Time
Automatic STORE to EEPROM
on Power Down using external
capacitor
Hardware or Software initiated
STORE
(STORE Cycle Time < 10 ms)
Automatic STORE Timing
10
5
STORE cycles to EEPROM
10 years data retention in
EEPROM
Automatic RECALL on Power Up
Software RECALL Initiation
(RECALL Cycle Time < 20
碌s)
Unlimited RECALL cycles from
EEPROM
Single 5 V
卤
10 % Operation
Operating temperature ranges:
0 to 70
掳C
-40 to 85
掳C
-40/-55 to 125 掳C (only 35 ns)
QS 9000 Quality Standard
ESD protection > 2000 V
(MIL STD 883C M3015.7-HBM)
Packages: SOP32 (300 mil),
PDIP32 (600 mil, only C/K-Type)
STORE cycles also may be initia-
ted under user control via a soft-
ware sequence or via a single pin
(HSB).
Once a STORE cycle is initiated,
further input or output are disabled
until the cycle is completed.
Because a sequence of addresses
is used for STORE initiation, it is
important that no other read or
write accesses intervene in the
sequence or the sequence will be
aborted.
RECALL cycles may also be initia-
ted by a software sequence.
Internally, RECALL is a two step
procedure. First, the SRAM data is
cleared and second, the nonvola-
tile information is transferred into
the SRAM cells.
The RECALL operation in no way
alters the data in the EEPROM
cells. The nonvolatile data can be
recalled an unlimited number of
times.
Pin Configuration
VCAP
A14
A12
A7
A6
A5
A4
A3
n.c.
A2
A1
A0
DQ0
DQ1
DQ2
VSS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Top View
Signal Name
A0 - A14
DQ0 - DQ7
E
G
W
VCCX
VSS
VCAP
HSB
Signal Description
Address Inputs
Data In/Out
Chip Enable
Output Enable
Write Enable
Power Supply Voltage
Ground
Capacitor
Hardware Controlled Store/Busy
PDIP
SOP
26
25
24
23
22
21
20
19
18
17
April 21, 2004
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