STK14C88_08 SIMTEK [Simtek Corporation], STK14C88_08 Datasheet - Page 10

• Manufacturer Part Number: STK14C88_08
• Description: 32Kx8 AutoStore nvSRAM
• Manufacturer: SIMTEK [Simtek Corporation]

STK14C88
Document Control #ML0014 Rev 2.0
SOFTWARE NONVOLATILE RECALL
A software
of
ware
the following sequence of
tions must be performed:
Internally,
SRAM
information is transferred into the
the t
ready for
operation in no way alters the data in the nonvolatile
elements. The nonvolatile data can be recalled an
unlimited number of times.
AutoStore MODE
The STK14C88 can be powered in one of three
modes.
During normal AutoStore operation, the STK14C88
will draw current from V
nected to the V
used by the chip to perform a single
tion. After power up, when the voltage on the V
pin drops below V
disconnect the V
STORE
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
READ
RECALL
Feb, 2008
STORE
data is cleared, and second, the nonvolatile
operation.
operations in a manner similar to the soft-
READ
RECALL
cycle time the
RECALL
initiation. To initiate the
and
CAP
CAP
is a two-step procedure. First, the
SWITCH
cycle is initiated with a sequence
pin. This stored charge will be
0E38 (hex)
31C7 (hex)
03E0 (hex)
3C1F (hex)
303F (hex)
0C63 (hex)
WRITE
pin from V
CC
, the part will automatically
to charge a capacitor con-
SRAM
E
operations. The
controlled
will once again be
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate RECALL cycle
CC
SRAM
RECALL
and initiate a
STORE
READ
cells. After
RECALL
opera-
opera-
cycle,
CAP
10
Figure 1 shows the proper connection of capacitors
for automatic store operation. A charge storage
capacitor having a capacity of between 68μF and
220μF (± 20%) rated at 6V should be provided.
In system power mode, both V
nected to the + 5V power supply without the 68μF
capacitor. In this mode the AutoStore function of the
STK14C88 will operate on the stored system charge
as power goes down. The user must, however,
guarantee that V
the 10ms
If an automatic
then V
V
in which the AutoStore function is disabled. If the
STK14C88 is operated in this configuration, refer-
ences to V
this data sheet. In this mode,
be triggered through software control or the HSB
pin. To enable or disable AutoStore using an IO port
pin, see “PREVENTING STORES” on page 12.
In order to prevent unneeded
automatic
externally driving HSB low will be ignored unless at
least one
most recent
initiated
whether a
If the power supply drops faster than 20 μs/volt
before V
should be inserted between V
ply to avoid momentary excess of current between
Vcc and Vcap.
CAP
(Figure 2). This is the AutoStore Inhibit mode,
CC
STORE
CC
can be tied to ground and + 5V applied to
WRITE
STORE
WRITE
CC
STORE
reaches V
should be changed to V
STORE
STORE
Figure 1: AutoStore Mode
cycles are performed regardless of
+
CC
operation has taken place since the
cycle.
operation has taken place.
s as well as those initiated by
does not drop below 3.6V during
SWITCH
or
on power loss is not required,
RECALL
1
16
, then a 2.2 ohm resistor
10kΩ∗
STORE
CC
CC
and the system sup-
STORE
32
31
30
17
and V
cycle. Software-
operations may
CAP
CAP
operations,
throughout
are con-