stk16c88-45i Simtek Corporation, stk16c88-45i Datasheet - Page 8

• Manufacturer Part Number: stk16c88-45i
• Description: 32kx8 Autostore+ Nvsram
• Manufacturer: Simtek Corporation

STK16C88
Document Control #ML0018 Rev 2.0
The AutoStore+ STK16C88 is a fast 32K x 8 SRAM
that does not lose its data on power-down. The data
is preserved in integral QuantumTrap non-volatile
storage elements when power is lost. Automatic
STORE on power-down and automatic RECALL on
power-up guarantee data integrity without the use of
batteries.
NOISE CONSIDERATIONS
Note that the STK16C88 is a high-speed memory
and so must have a high-frequency bypass capaci-
tor of approximately 0.1μF connected between V
and V
possible. As with all high-speed
careful routing of power, ground and signals will help
prevent noise problems.
SRAM READ
The STK16C88 performs a
and G are low and W is high. The address specified
on pins A
bytes will be accessed. When the
by an address transition, the outputs will be valid
after a delay of t
initiated by E or G, the outputs will be valid at t
at t
outputs will repeatedly respond to address changes
within the t
sitions on any control input pins, and will remain valid
until another address change or until E or G is
brought high.
SRAM WRITE
A
low. The address inputs must be stable prior to
entering the
until either E or W goes high at the end of the cycle.
The data on the common I/O pins DQ
ten into the memory if it is valid t
of a W controlled
E controlled
It is recommended that G be kept high during the
entire
the common I/O lines. If G is left low, internal circuitry
will turn off the output buffers t
WRITE
GLQV
Jan, 2008
SS
WRITE
, whichever is later (
, using leads and traces that are as short as
cycle is performed whenever E and W are
0-14
AVQV
WRITE
WRITE
determines which of the 32,768 data
cycle to avoid data bus contention on
access time without the need for tran-
AVQV
WRITE
.
(
cycle and must remain stable
READ
or t
READ
READ
cycle #1). If the
DVEH
WLQZ
before the end of an
DVWH
cycle #2). The data
CMOS
cycle whenever E
after W goes low.
READ
nvSRAM OPERATION
before the end
0-7
ICs, normal
will be writ-
is initiated
READ
ELQV
CC
or
is
8
AutoStore+ OPERATION
The STK16C88’s automatic STORE on power-down
is completely transparent to the system. The
STORE initiation takes less than 500ns when power
is lost (V
only on its internal capacitor for STORE completion.
If the power supply drops faster than 20 μs/volt
before Vcc reaches Vswitch, then a 2.2 ohm resistor
should be inserted between Vcc and the system
supply to avoid a momentary excess of current
between Vcc and internal capacitor.
In order to prevent unneeded STORE operations,
automatic STOREs will be ignored unless at least
one WRITE operation has taken place since the
most recent STORE or RECALL cycle. Software
initiated STORE cycles are performed regardless of
whether or not a WRITE operation has taken place.
POWER-UP RECALL
During power up, or after any low-power condition
(V
latched. When V
voltage of V
be initiated and will take t
If the STK16C88 is in a WRITE state at the end of
power-up RECALL, the SRAM data will be cor-
rupted. To help avoid this situation, a 10kΩ resistor
should be connected either between W and system
V
SOFTWARE NONVOLATILE STORE
The STK16C88 software STORE cycle is initiated
by executing sequential READ cycles from six spe-
cific address locations. During the STORE cycle,
previous non-volatile data is erased and then the
SRAM contents are written to the non-volatile stor-
age elements. Once a STORE cycle is initiated, fur-
ther inputs and outputs are disabled until the cycle is
completed.
Because a sequence of READs from specific
addresses is used for STORE initiation, it is impor-
tant that no other READ or WRITE accesses inter-
vene in the sequence or the sequence will be
aborted and no STORE or RECALL will take place.
To initiate the software STORE cycle, the following
READ
CC
CC
or between E and system V
< V
sequence must be performed:
CC
RESET
< V
SWITCH
), an internal RECALL request will be
SWITCH
, a RECALL cycle will automatically
CC
) at which point the part depends
once again exceeds the sense
RESTORE
CC
to complete.
.