STK14C88-3 Simtek, STK14C88-3 Datasheet - Page 11

• Manufacturer Part Number: STK14C88-3
• Description: 32Kx8 AutoStore nvSRAM
• Manufacturer: Simtek

Document Control #ML0015 Rev 0.6
SOFTWARE NONVOLATILE RECALL
A software
of
ware
the following sequence of
tions must be performed:
Internally,
SRAM
information is transferred into the
the t
ready for
operation in no way alters the data in the nonvolatile
elements. The nonvolatile data can be recalled an
unlimited number of times.
AutoStore OPERATION
The STK14C88-3 can be powered in one of three
modes.
During normal AutoStore operation, the STK14C88-
3 will draw current from V
connected to the V
used by the chip to perform a single
tion. After power up, when the voltage on the V
pin drops below V
disconnect the V
STORE
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
automatic
externally driving HSB low will be ignored unless at
least one
most recent
initiated
whether a
If the power supply drops faster than 20 μs/volt
before V
should be inserted between V
supply to avoid momentary excess of current
between Vccx and Vcap.
1. Read address
2. Read address
3. Read address
4. Read address
5. Read address
6. Read address
READ
RECALL
February 2007
STORE
data is cleared, and second, the nonvolatile
operation.
STORE
CCX
operations in a manner similar to the soft-
READ
WRITE
RECALL
WRITE
cycle time the
RECALL
STORE
reaches V
initiation. To initiate the
STORE
and
cycles are performed regardless of
operation has taken place since the
operation has taken place.
CAP
s as well as those initiated by
is a two-step procedure. First, the
CAP
SWITCH
cycle is initiated with a sequence
0E38 (hex)
31C7 (hex)
03E0 (hex)
3C1F (hex)
303F (hex)
0C63 (hex)
WRITE
pin from V
pin. This stored charge will be
or
SWITCH
, the part will automatically
RECALL
SRAM
CCX
E
operations. The
, then a 1 ohm resistor
controlled
to charge a capacitor
CCX
STORE
will once again be
CCX
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate RECALL cycle
SRAM
cycle. Software-
and the system
RECALL
STORE
and initiate a
READ
operations,
cells. After
RECALL
opera-
opera-
cycle,
CAP
11
HSB OPERATION
The STK14C88-3 provides the HSB pin for control-
ling and acknowledging the
HSB pin can be used to request a hardware
cycle. When the HSB pin is driven low, the
STK14C88-3 will conditionally initiate a
ation after t
begin if a
last
as an open drain driver that is internally driven low
to indicate a busy condition while the
ated by any means) is in progress. Pull up this pin
with an external 10K ohm resistor to V
used as a driver.
SRAM READ
progress when HSB is driven low by any means are
given time to complete before the
is initiated. After HSB goes low, the STK14C88-3
will continue
multiple
WRITE
be allowed a time, t
SRAM WRITE
will be inhibited until HSB returns high.
The HSB pin can be used to synchronize multiple
STK14C88-3s while using a single larger capacitor.
To operate in this mode the HSB pin should be con-
nected together to the HSB pins from the other
STK14C88-3s. An external pull-up resistor to +3.3V
is required since HSB acts as an open drain pull-
down. The V
*If HSB is not used, it should be left unconnected.
STORE
is in progress when HSB is pulled low it will
SRAM READ
WRITE
or
DELAY
Figure 2: AutoStore Mode
+
SRAM
CAP
cycles requested after HSB goes low
RECALL
and
; an actual
pins from the other STK14C88-3
to the
operations for t
WRITE
DELAY
10kO*
operations may take place. If a
cycle. The HSB pin also acts
1
16
, to complete. However, any
SRAM
operations that are in
STORE
STORE
31
30
17
32
took place since the
DELAY
STORE
STK14C88-3
operations. The
cycle will only
. During t
CAP
STORE
STORE
operation
if HSB is
STORE
oper-
(initi-
DELAY
,