STK14C88-3WF45ITR データシートの表示（PDF） - Simtek Corporation
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STK14C88-3WF45ITR Datasheet PDF : 18 Pages
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STK14C88-3
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
2. Read address
3. Read address
4. Read address
5. Read address
6. 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
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 tRECALL 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 MODE
The STK14C88-3 can be powered in one of three
modes.
During normal AutoStore operation, the STK14C88-
3 will draw current from VCC to charge a capacitor
connected to the VCAP 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 VCAP
pin drops below VSWITCH, the part will automatically
disconnect the VCAP pin from VCC 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 68μF and
220μF (± 20%) rated at 4.7V should be provided.
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.
If the power supply drops faster than 20 μs/volt
before VCC reaches VSWITCH, then a 1 ohm resistor
should be inserted between VCC and the system sup-
ply to avoid momentary excess of current between
Vcc and Vcap.
10kO*
1
32
31
30
+
16
17
Figure 2: AutoStore Mode
*If HSB is not used, it should be left unconnected.
AutoStore INHIBIT MODE
If an automatic STORE on power loss is not
required, then Vcc can be tied to ground and system
power applied to VCAP (Figure 3). This is the
AutoStore Inhibit mode, in which the AutoStore func-
tion is disabled. If the STK14C88-3 is operated in
this configuration, references to Vcc should be
changed to VCAP throughout this data sheet. In this
mode, STORE operations may be triggered through
software control. It is not permissible to change
between these three options “on the fly.”
1
32
31
30
16
17
Figure 3: AutoStore Inhibit Mode
*If HSB is not used, it should be left unconnected.
Document Control #ML0015 Rev 2.0
11
Feb, 2008
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