STK14C88 Simtek, STK14C88 Datasheet - Page 10

• Manufacturer Part Number: STK14C88
• Description: 32Kx8 AutoStore nvSRAM
• Manufacturer: Simtek

STK14C88
Document Control #ML0014 Rev 0.3
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 OPERATION
The STK14C88 can be powered in one of three
modes.
During normal AutoStore operation, the STK14C88
will draw current from V
connected 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
*If HSB is not used, it should be left unconnected.
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
READ
Figure 2: AutoStore Mode
RECALL
February, 2007
+
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
1
16
and
10kΩ∗
CAP
is a two-step procedure. First, the
CAP
SWITCH
cycle is initiated with a sequence
0E38 (hex)
31C7 (hex)
03E0 (hex)
3C1F (hex)
303F (hex)
0C63 (hex)
WRITE
32
31
30
17
pin from V
pin. This stored charge will be
, the part will automatically
CCX
SRAM
E
operations. The
controlled
to charge a capacitor
will once again be
CCX
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate RECALL cycle
SRAM
RECALL
STORE
and initiate a
READ
Figure 3: System Power Mode
cells. After
RECALL
opera-
opera-
cycle,
CAP
1
16
10
32
31
30
17
Figure 2 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 (Figure 3), both V
V
the 68μF capacitor. In this mode the AutoStore func-
tion of the STK14C88 will operate on the stored sys-
tem charge as power goes down. The user must,
however, guarantee that V
3.6V during 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. It is not permissable to change between these
three options “on the fly”.
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
supply to avoid momentary excess of current
between Vccx and Vcap.
CAP
CAP
are connected to the + 5V power supply without
(Figure 4). This is the AutoStore Inhibit mode,
CCX
STORE
CCX
WRITE
can be tied to ground and + 5V applied to
WRITE
CCX
STORE
reaches V
should be changed to V
STORE
STORE
cycles are performed regardless of
operation has taken place since the
operation has taken place.
s as well as those initiated by
STORE
SWITCH
or
on power loss is not required,
Figure 4: AutoStore
RECALL
CCX
, then a 2.2 ohm resistor
Inhibit Mode
STORE
cycle.
1
16
does not drop below
CCX
STORE
cycle. Software-
and the system
operations may
32
31
30
17
CAP
operations,
throughout
CCX
and