STK11C88
July 1999
5-8
Internally, RECALL is a two-step procedure. First,
the SRAM data is cleared, and second, the nonvola-
tile 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 unlimited number of times.
POWER-UP RECALL
During power up, or after any low-power condition
(V
CC < VRESET), an internal RECALL request will be
latched. When V
CC once again exceeds the sense
voltage of V
SWITCH, a RECALL cycle will automatically
be initiated and will take t
RESTORE to complete.
If the STK11C88 is in a WRITE state at the end of
power-up RECALL, the SRAM data will be corrupted.
To help avoid this situation, a 10K Ohm resistor
should be connected either between W and system
V
CC or between E and system VCC.
HARDWARE PROTECT
The STK11C88 offers hardware protection against
inadvertent STORE operation during low-voltage
conditions. When V
CC < VSWITCH, all software STORE
operations are inhibited.
LOW AVERAGE ACTIVE POWER
The STK11C88 draws significantly less current
when it is cycled at times longer than 50ns. Figure 2
shows the relationship between I
CC and READ cycle
time. Worst-case current consumption is shown for
both CMOS and TTL input levels (commercial tem-
perature range, V
CC = 5.5V, 100% duty cycle on
chip enable). Figure 3 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 cur-
rent drawn by the STK11C88 depends on the fol-
lowing 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.
0
20
40
60
80
100
50
100
150
200
Cycle Time (ns)
TTL
CMOS
100