STK16CA8 Ver la hoja de datos (PDF) - Simtek Corporation
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STK16CA8 Datasheet PDF : 12 Pages
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STK16CA8
valid. After the tSTORE cycle time has been fulfilled,
the SRAM will again be activated for READ and
WRITE operation.
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
4E38 (hex)
B1C7 (hex)
83E0 (hex)
7C1F (hex)
703F (hex)
4C63 (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.
HARDWARE PROTECT
The STK16CA8 offers hardware protection against
inadvertent STORE operation and SRAM WRITEs dur-
ing low-voltage conditions. When VCCX < VSWITCH, all
externally initiated STORE operations and SRAM
WRITEs will be inhibited.
PREVENTING STORES
The AutoStore™ function can be disabled on the fly
by initiating an AutoStore Inhibit sequence. A
sequence of read operations is performed in a man-
ner similar to the software STORE initiation. To ini-
tiate the AutoStore Inihibit sequence, the following
sequence of E controlled read operations must be
performed:
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
4E38 (hex)
B1C7 (hex)
83E0 (hex)
7C1F (hex)
703F (hex)
8B45 (hex)
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
AutoStore Inhibit
sequence has been performed, regardless of device
power cycles.
The AutoStore Inhibit can be disabled by initiating
an AutoStore Inhibit Off sequence. A sequence of
read operations is performed in a manner similar to
the software RECALL initiation. To initiate the
AutoStore Inhibit Off sequence, the following
sequence of E controlled read operations must be
performed:
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
4E38 (hex)
B1C7 (hex)
83E0 (hex)
7C1F (hex)
703F (hex)
4B46 (hex)
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
AutoStore Inhibit Off
LOW AVERAGE ACTIVE POWER
The STK16CA8 draws significantly less current
when it is cycled at times longer than 50ns. Figure 3
shows the relationship between ICC and READ cycle
time. Worst-case current consumption is shown for
both CMOS and TTL input levels (commercial tem-
perature range, VCC = 3.6V, 100% duty cycle on chip
enable). Figure 4 shows the same relationship for
WRITE cycles. If the chip enable duty cycle is less
than 100%, only standby current is drawn when the
chip is disabled. The overall average current drawn
by the STK16CA8 depends on the following items:
1) CMOS vs. TTL input levels; 2) the duty cycle of
chip enable; 3) the overall cycle rate for accesses;
4) the ratio of READs to WRITEs; 5) the operating
temperature; 6) the Vcc level; and 7) I/O loading.
Once the AutoStore™ inhibit has been initiated, it
will remain active until an AutoStore™ inhibit off
September 2003
9 Document Control # ML0023 rev 0.1
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