STK14CA8
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.
NOISE CONSIDERATIONS
The STK14CA8 is a high-speed memory and so must
have high-frequency bypass capacitor of
a
approximately 0.1µF connected between VCC and VSS,
using leads and traces that are as short as possible.
As with all high-speed CMOS ICs, careful routing of
power, ground and signals will reduce circuit noise.
PREVENTING AUTOSTORETM
LOW AVERAGE ACTIVE POWER
The AutoStore™ function can be disabled by initiat-
ing an AutoStore Disable sequence. A sequence of
read operations is performed in a manner similar to
the software STORE initiation. To initiate the
AutoStore Disable sequence, the following sequence
CMOS technology provides the STK14CA8 this the
benefit of drawing significantly less current when it is
cycled at times longer than 50ns. Figure 5 shows the
relationship between ICC and READ/WRITE cycle
time. Worst-case current consumption is shown for
commercial temperature range, VCC = 3.6V, and chip
enable at maximum frequency. Only standby current
is drawn when the chip is disabled. The overall
average current drawn by the STK14CA8 depends on
the following items:
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
0x4E38
0xB1C7
0x83E0
0x7C1F
0x703F
0x8B45
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
AutoStore Disable
1. The duty cycle of chip enable.
2. The overall cycle rate for accesses.
3. The ratio of READs to WRITEs.
4. The operating temperature.
5. The VCC level.
The AutoStore™ can be re-enabled by initiating an
AutoStore Enable sequence. A sequence of read
operations is performed in a manner similar to the
software RECALL initiation. To initiate the AutoStore
Enable sequence, the following sequence of
E
6. I/O loading.
controlled read operations must be performed:
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
0x4E38
0xB1C7
0x83E0
0x7C1F
0x703F
0x4B46
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
AutoStore Enable
50
40
30
If the AutoStore™ function is disabled or re-enabled
a manual STORE operation (Hardware or Software)
needs to be issued to save the AutoStore state
through subsequent power down cycles. The part
comes from the factory with AutoStore™ enabled.
Writes
20
DATA PROTECTION
10
Reads
The STK14CA8 protects data from corruption during
low-voltage conditions by inhibiting all externally
initiated STORE and WRITE operations. The low-
voltage condition is detected when VCC < VSWITCH .
0
If the STK14CA8 is in a WRITE mode (both E and
W low ) at power-up, after a RECALL, or after a
STORE, the WRITE will be inhibited until a negative
50 100 150 200 300
Cycle Time (ns)
transition on
E
or
W
is detected. This protects
against inadvertent writes during power up or brown
out conditions.
Figure 5 Current vs. Cycle time
December 2004
13
Document Control #ML0022 rev 1.0
SIMTEK [ SIMTEK CORPORATION ]
