STK14C88
SOFTWARE NONVOLATILE
RECALL
A software
RECALL
cycle is initiated with a sequence
of
READ
operations in a manner similar to the soft-
ware
STORE
initiation. To initiate the
RECALL
cycle,
the following sequence of
E
controlled
READ
opera-
tions must be performed:
1.
2.
3.
4.
5.
6.
Read address
Read address
Read address
Read address
Read address
Read address
0E38 (hex)
31C7 (hex)
03E0 (hex)
3C1F (hex)
303F (hex)
0C63 (hex)
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate
RECALL
cycle
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
CCX
and
V
CAP
are connected to the + 5V power supply without
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
CCX
does not drop below
3.6V during the 10ms
STORE
cycle.
If an automatic
STORE
on power loss is not required,
then V
CCX
can be tied to ground and + 5V applied to
V
CAP
(Figure 4). This is the AutoStore Inhibit mode,
in which the AutoStore function is disabled. If the
STK14C88 is operated in this configuration, refer-
ences to V
CCX
should be changed to V
CAP
throughout
this data sheet. In this mode,
STORE
operations may
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
STORE
operations,
automatic
STORE
s as well as those initiated by
externally driving HSB low 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 a
WRITE
operation has taken place.
If the power supply drops faster than 20
μs/volt
before V
CCX
reaches V
SWITCH
, then a 2.2 ohm resistor
should be inserted between V
CCX
and the system
supply to avoid momentary excess of current
between Vccx and Vcap.
10kΩ∗
0.1μF
Bypass
10kΩ∗
1
32
31
30
16
17
Internally,
RECALL
is a two-step procedure. First, the
SRAM
data is cleared, and second, the nonvolatile
information is transferred into the
SRAM
cells. After
the t
RECALL
cycle time the
SRAM
will once again be
ready for
READ
and
WRITE
operations. The
RECALL
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
CCX
to charge a capacitor
connected to the V
CAP
pin. This stored charge will be
used by the chip to perform a single
STORE
opera-
tion. After power up, when the voltage on the V
CAP
pin drops below V
SWITCH
, the part will automatically
disconnect the V
CAP
pin from V
CCX
and initiate a
STORE
operation.
10kΩ∗
10kΩ
1
32
31
30
1
32
31
30
68μF
6v, ±20%
+
0.1μF
Bypass
0.1μF
Bypass
16
16
17
17
Figure 2: AutoStore Mode
Figure 3: System Power Mode
Figure 4: AutoStore
Inhibit Mode
*If HSB is not used, it should be left unconnected.
Document Control #ML0014 Rev 0.3
February, 2007
10
10kΩ
10kΩ
SIMTEK [ SIMTEK CORPORATION ]
