STK22C48-W45I Cypress Semiconductor Corp, STK22C48-W45I Datasheet - Page 8

• Manufacturer Part Number: STK22C48-W45I
• Manufacturer: Cypress Semiconductor Corp
• Type: NVSRAMr

Specifications of STK22C48-W45I

• Word Size: 8b
• Organization: 2Kx8
• Density: 16Kb
• Interface Type: Parallel
• Access Time (max): 45ns
• Operating Supply Voltage (typ): 5V
• Package Type: PDIP
• Operating Temperature Classification: Industrial
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• Operating Temp Range: -40C to 85C
• Pin Count: 28
• Mounting: Through Hole
• Supply Current: 65mA
• Lead Free Status / Rohs Status: Not Compliant

*If HSB is not used, it should be left unconnected.
STK22C48
July 1999
In order to prevent unneeded
automatic
externally driving HSB low will be ignored unless at
least one
most recent
pull-up resistor is shown connected to HSB. This
can be used to signal the system that the
AutoStore™ cycle is in progress.
HSB OPERATION
The STK22C48 provides the HSB pin for controlling
and acknowledging the
pin is used to request a hardware
When the HSB pin is driven low, the STK22C48 will
conditionally initiate a
an actual
the
RECALL
driver that is internally driven low to indicate a busy
condition while the
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 STK22C48 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
STK22C48s while using a single larger capacitor. To
Figure 2: AutoStore™ Mode
SRAM
+
is in progress when HSB is pulled low it will
SRAM READ
cycle. The HSB pin acts as an open drain
WRITE
SRAM
STORE
STORE
took place since the last
STORE
cycles requested after HSB goes low
and
1
14
operation has taken place since the
operations for t
cycle will only begin if a
s as well as those initiated by
STORE
WRITE
DELAY
operations may take place. If a
or
28
27
26
15
STORE
STORE
, to complete. However, any
RECALL
(initiated by any means)
operations that are in
operation after t
operations. The HSB
STORE
DELAY
cycle. An optional
STORE
. During t
STORE
Figure 3: System Power Mode
operations,
STORE
operation
WRITE
cycle.
DELAY
DELAY
1
14
or
to
3-28
;
,
28
27
26
15
operate in this mode the HSB pin should be con-
nected together to the HSB pins from the other
STK22C48s. 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
STK22C48s detects a power loss and asserts HSB,
the common HSB pin will cause all parts to request
a
STK22C48s that have been written since the last
nonvolatile cycle).
During any
was initiated, the STK22C48 will continue to drive
the HSB pin low, releasing it only when the
complete. Upon completion of the
the STK22C48 will remain disabled until the HSB
pin returns high.
If HSB is not used, it should be left unconnected.
PREVENTING STORES
The
holding HSB high with a driver capable of sourcing
30mA at a VOH of at least 2.2V, as it will have to
overpower the internal pull-down device that drives
HSB low for 20µs at the onset of a
the STK22C48 is connected for AutoStore™ opera-
tion (system V
capacitor on V
way down, the STK22C48 will attempt to pull HSB
low; if HSB doesn’t actually get below V
STORE
STORE
CAP
pins from the other STK22C48 parts can
cycle (a
STORE
function can be disabled on the fly by
CAP
CC
) and V
connected to V
STORE
operation, regardless of how it
Figure 4: AutoStore™
CC
will take place in those
crosses V
Inhibit Mode
1
14
STORE
CCX
28
27
26
15
STORE
SWITCH
and a 68µF
IL
operation
, the part
STORE
. When
on the
is