STK14C88-M Simtek, STK14C88-M Datasheet - Page 10

• Manufacturer Part Number: STK14C88-M
• Description: 32K x 8 AUTOSTORE nvSRAM QUANTUM TRAP CMOS NONVOLATILE STATIC RAM
• Manufacturer: Simtek

STK14C88-M
April 1999
HSB OPERATION
The STK14C88-M 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-M will conditionally initiate a
operation after t
begin if a
last
an open drain driver that is internally driven low to
indicate a busy condition while the
by any means) is in progress.
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-M
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-Ms 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-Ms. An external pull-up resistor to + 5V
is required since HSB acts as an open drain pull
down. The V
parts can be tied together and share a single capac-
itor. The capacitor size must be scaled by the num-
ber of devices connected to it. When any one of the
STK14C88-Ms detects a power loss and asserts
HSB, the common HSB pin will cause all parts to
request a
those STK14C88-Ms that have been written since
the last nonvolatile cycle).
During any
was initiated, the STK14C88-M will continue to drive
the HSB pin low, releasing it only when the
complete. Upon completion of the
the STK14C88-M will remain disabled until the HSB
pin returns high.
If HSB is not used, it should be left unconnected.
STORE
is in progress when HSB is pulled low it will
SRAM READ
WRITE
STORE
or
STORE
SRAM
CAP
cycles requested after HSB goes low
and
RECALL
DELAY
pins from the other STK14C88-M
to the
cycle (a
operations for t
; an actual
WRITE
DELAY
operation, regardless of how it
operations may take place. If a
cycle. The HSB pin acts as
, to complete. However, any
SRAM
STORE
operations that are in
STORE
STORE
took place since the
DELAY
STORE
will take place in
STORE
STORE
operations. The
cycle will only
. During t
operation
operation
STORE
(initiated
STORE
STORE
DELAY
is
5-52
,
PREVENTING STORES
The
holding HSB high with a driver capable of sourcing
30mA at a V
power the internal pull-down device that drives HSB
low for 20 s at the onset of a
STK14C88-M is connected for AutoStore ™ opera-
tion (system V
capacitor on V
way down, the STK14C88-M will attempt to pull HSB
low; if HSB doesn’t actually get below V
will stop trying to pull HSB low and abort the
attempt.
HARDWARE PROTECT
The
against inadvertent
WRITE
V
SRAM WRITE
AutoStore ™ can be completely disabled by tying
V
AutoStore ™ Inhibit mode;
by explicit request using either the software
sequence or the HSB pin in this mode.
LOW AVERAGE ACTIVE POWER
The STK14C88-M will draw significantly less current
when it is cycled at times longer than 50ns. Figure 5
shows the relationship between I
time. Worst-case current consumption is shown for
both
perature range, V
enable). Figure 6 shows the same relationship for
WRITE
than 100%, only standby current is drawn when the
chip is disabled.
The
STK14C88-M depends on the following items:
1)
chip enable; 3) the overall cycle rate for accesses;
4) the ratio of
temperature; 6) the V
SWITCH
CCX
CMOS
STORE
to ground and applying + 5V to V
CMOS
STK14C88-M
s during low-voltage conditions. When V
overall
, all externally initiated
cycles. If the chip enable duty cycle is less
vs.
OH
and
function can be disabled on the fly by
s are inhibited.
TTL
of at least 2.2V, as it will have to over-
CAP
READ
average
CC
TTL
CC
) and V
input levels; 2) the duty cycle of
connected to V
= 5.5V, 100% duty cycle on chip
s to
CC
STORE
input levels (commercial tem-
offers
level; and 7) I/O loading.
CC
current
WRITE
STORE
crosses V
STORE
operation and
hardware
s; 5) the operating
STORE
CC
s are only initiated
CCX
drawn
and
operations and
CAP
and a 68 F
SWITCH
. When the
. This is the
READ
IL
protection
, the part
by
STORE
on the
SRAM
cycle
CAP
the
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