stk14c88-n25m Simtek Corporation, stk14c88-n25m Datasheet - Page 11

• Manufacturer Part Number: stk14c88-n25m
• Description: 32kx8 Autostore Nvsram
• Manufacturer: Simtek Corporation

Document Control #ML0014 Rev 2.0
AutoStore INHIBIT MODE
If an automatic STORE on power loss is not
required, then V
tem power applied to V
AutoStore Inhibit Mode, in which the AutoStore func-
tion is disabled. If the STK14C88 is operated in this
configuration, references to V
to V
STORE operations may be triggered through soft-
ware control. It is not permissible to change
between these three options “on the fly.”
HSB OPERATION
The STK14C88 provides the HSB pin for controlling
and acknowledging the
pin can be used to request a hardware
When the HSB pin is driven low, the STK14C88 will
conditionally initiate a
an actual
the
RECALL
pullup and is internally driven low to indicate a busy
condition while the
is in progress. Pull up this pin with an external 10K
ohm resistor to V
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 will
continue
multiple
WRITE
CAP
SRAM
Feb, 2008
is in progress when HSB is pulled low it will
SRAM READ
cycle. The HSB pin has a very resistive
throughout this data sheet. In this mode,
SRAM
STORE
Figure 2: AutoStore Inhibit Mode
took place since the last
and
CC
operations for t
CAP
cycle will only begin if a
STORE
WRITE
can be tied to ground and sys-
operations may take place. If a
if HSB is used as a driver.
1
16
STORE
STORE
CAP
(initiated by any means)
operations that are in
(Figure 2). This is the
CC
operation after t
operations. The HSB
17
32
31
30
should be changed
DELAY
STORE
. During t
STORE
STORE
operation
WRITE
cycle.
DELAY
DELAY
to
or
11
;
,
be allowed a time, t
SRAM WRITE
will be inhibited until HSB returns high.
The HSB pin can be used to synchronize multiple
STK14C88s 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
STK14C88s. An external pull-up resistor to + 5V is
required since HSB acts as an open drain pull down.
The V
be tied together and share a single capacitor. The
capacitor size must be scaled by the number of
devices connected to it. When any one of the
STK14C88s detects a power loss and asserts HSB,
the common HSB pin will cause all parts to request
a
STK14C88s that have been written since the last
nonvolatile cycle).
During any
was initiated, the STK14C88 will continue to drive
the HSB pin low, releasing it only when the
complete. Upon completion of the
the STK14C88 will remain disabled until the HSB
pin returns high.
If HSB is not used, it should be left unconnected.
BEST PRACTICES
nvSRAM products have been used effectively for
over 15 years. While ease-of-use is one of the prod-
uct’s main system values, experience gained work-
ing with hundreds of applications has resulted in the
following suggestions as best practices:
• The non-volatile cells in an nvSRAM are pro-
STORE
grammed on the test floor during final test and
quality assurance. Incoming inspection routines
at customer or contract manufacturer’s sites will
sometimes reprogram these values. Final NV pat-
terns are typically repeating patterns of AA, 55,
00, FF, A5, or 5A. End product’s firmware should
not assume an NV array is in a set programmed
state. Routines that check memory content val-
ues to determine first time system configuration,
cold or warm boot status, etc. should always pro-
gram a unique NV pattern (e.g., complex 4-byte
pattern of 46 E6 49 53 hex or more random
bytes) as part of the final system manufacturing
test to ensure these system routines work consis-
tently.
CAP
pins from the other STK14C88 parts can
cycle (a
STORE
cycles requested after HSB goes low
STORE
DELAY
operation, regardless of how it
, to complete. However, any
will take place in those
STORE
STK14C88
operation
STORE
is