stk14ee8-tf45tr Simtek Corporation, stk14ee8-tf45tr Datasheet - Page 12

• Manufacturer Part Number: stk14ee8-tf45tr
• Description: 1mx8 Autostore Nvsram
• Manufacturer: Simtek Corporation

STK14EE8
Document Control #ML0068 Rev 1.0
To reduce unneeded nonvolatile stores, AutoStore
and Hardware Store operations 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 per-
formed regardless of whether a WRITE operation
has taken place. The HSB signal can be monitored
by the system to detect an AutoStore cycle is in
progress.
HARDWARE STORE (HSB) OPERATION
The STK14EE8 provides the HSB pin for controlling
and acknowledging the STORE operations. The
HSB pin can be used to request a hardware STORE
cycle. When the HSB pin is driven low, the
STK14EE8 will conditionally initiate a STORE opera-
tion after t
begin if a WRITE to the SRAM took place since the
last STORE or RECALL cycle. The HSB pin has a
very resistive pullup and is internally driven low to
indicate a busy condition while the STORE (initiated
by any means) is in progress. This pin should be
externally pulled up if it is used to drive other inputs.
SRAM READ and WRITE operations that are in
progress when HSB is driven low or when V
below V
STORE operation is initiated. After AUTOSTORE or
HSB goes low, the STK14EE8 will continue to allow
SRAM operations for t
SRAM READ operations may take place. If a WRITE
is in progress when HSB is pulled low, it will be
allowed a time, t
SRAM WRITE cycles requested after HSB goes low
will be inhibited until HSB returns high.
If HSB is not used, it should be left unconnected.
HARDWARE RECALL (POWER-UP)
During power up or after any low-power condition
(V
latched. When V
voltage of V
cally be initiated and will take t
SOFTWARE STORE
Data can be transferred from the SRAM to the non-
volatile memory by a software address sequence.
The STK14EE8 software STORE cycle is initiated by
executing sequential E controlled or G controlled
CC
<V
March, 2008
SWITCH
switch
DELAY
SWITCH
are given time to complete before the
), an internal RECALL request will be
. An actual STORE cycle will only
CC
DELAY
, a RECALL cycle will automati-
once again exceeds the sense
DELAY
, to complete. However, any
. During t
HRECALL
DELAY
to complete.
Simtek Confidential
, multiple
CC
falls
12
READ cycles from six specific address locations in
exact order. During the STORE cycle, previous data
is erased and then the new data is programmed into
the nonvolatile elements. Once a STORE cycle is
initiated, further memory inputs and outputs are dis-
abled until the cycle is completed.
To initiate the software STORE cycle, the following
READ sequence must be performed:
Once the sixth address in the sequence has been
entered, the STORE cycle will commence and the
chip will be disabled. It is important that READ
cycles and not WRITE cycles be used in the
sequence and that G is active. After the t
time has been fulfilled, the SRAM will again be acti-
vated for READ and WRITE operation.
SOFTWARE RECALL
Data can be transferred from the nonvolatile mem-
ory to the SRAM by a software address sequence. 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 or G con-
trolled READ operations must be performed:
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
again be ready for READ or WRITE operations. The
RECALL operation in no way alters the data in the
nonvolatile storage elements. Care must be taken
so the controlling falling edge is glitch and ring free
so as not to double clock the read address.
1 Read Address
2 Read Address
3 Read Address
4 Read Address
5 Read Address
6 Read Address
1 Read Address
2 Read Address
3 Read Address
4 Read Address
5 Read Address
6 Read Address
RECALL
Preliminary
cycle time, the SRAM will once
0x04E38
0x0B1C7
0x083E0
0x07C1F
0x0703F
0x08FC0
0x04E38
0x0B1C7
0x083E0
0x07C1F
0x0703F
0x04C63
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate RECALL Cycle
Valid READ
Valid READ
Valid READ
Valid READ
Valid READ
Initiate STORE Cycle
STORE
cycle