STK14C88-M
April 1999
5-51
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.
Read address
0E38 (hex)
Valid READ
2.
Read address
31C7 (hex)
Valid READ
3.
Read address
03E0 (hex)
Valid READ
4.
Read address
3C1F (hex)
Valid READ
5.
Read address
303F (hex)
Valid READ
6.
Read address
0C63 (hex)
Initiate
RECALL cycle
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 EEPROM
cells. The nonvolatile data can be recalled an unlim-
ited number of times.
AutoStore™ OPERATION
The STK14C88-M can be powered in one of three
modes.
During
normal
AutoStore™
operation,
the
STK14C88-M 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
operation. After power up, when the voltage
on the V
CAP pin drops below VSWITCH, the part will
automatically disconnect the V
CAP pin from VCCX and
initiate a STORE operation.
Figure 2 shows the proper connection of capacitors
for automatic store operation. A charge storage
capacitor having a capacity of between 68
µF and
220
µF (± 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 100
µF capacitor. In this mode the AutoStore™
function of the STK14C88-M will operate on the
stored system 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-M is operated in this configuration,
references to V
CCX
should be changed to V
CAP
throughout this data sheet. In this mode, STORE
operations may be triggered through software con-
trol 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 STOREs 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. An
optional pull-up resistor is shown connected to HSB.
This can be used to signal the system that the
AutoStore™ cycle is in progress.
Figure 2:
AutoStore™ Mode
1
16
32
31
17
30
+
10k
Ω∗
Figure 3: System Power Mode
1
16
32
31
17
30
Figure 4:
AutoStore™
Inhibit Mode
1
16
32
31
17
30
*If HSB is not used, it should be left unconnected.