Cypress Semiconductor STK14C88-5 Fiche technique - Page 4
Parcourez en ligne ou téléchargez le pdf Fiche technique pour {nom_de_la_catégorie} Cypress Semiconductor STK14C88-5. Cypress Semiconductor STK14C88-5 18 pages. 256 kbit (32k x 8) autostore nvsram
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Figure 4. AutoStore Inhibit Mode
Hardware STORE (HSB) Operation
The STK14C88-5 provides the HSB pin for controlling and
acknowledging the STORE operations. The HSB pin is used to
request a hardware STORE cycle. When the HSB pin is driven
LOW, the STK14C88-5 conditionally initiates a STORE
operation after t
. An actual STORE cycle only begins if a
DELAY
WRITE to the SRAM takes place since the last STORE or
RECALL cycle. The HSB pin also acts as an open drain driver
that is internally driven LOW to indicate a busy condition, while
the STORE (initiated by any means) is in progress. Pull up this
pin with an external 10K ohm resistor to V
a driver.
SRAM READ and WRITE operations, that are in progress when
HSB is driven LOW by any means, are given time to complete
before the STORE operation is initiated. After HSB goes LOW,
the STK14C88-5 continues SRAM operations for t
t
, multiple SRAM READ operations take place. If a WRITE
DELAY
is in progress when HSB is pulled LOW, it allows a time, t
to complete. However, any SRAM WRITE cycles requested after
HSB goes LOW are inhibited until HSB returns HIGH.
During any STORE operation, regardless of how it is initiated,
the STK14C88-5 continues to drive the HSB pin LOW, releasing
it only when the STORE is complete. After completing the
STORE operation, the STK14C88-5 remains disabled until the
HSB pin returns HIGH.
If HSB is not used, it is left unconnected.
Hardware RECALL (Power Up)
During power up or after any low power condition (V
V
), an internal RECALL request is latched. When V
RESET
once again exceeds the sense voltage of V
cycle is automatically initiated and takes t
Document Number: 001-51038 Rev. **
If the STK14C88-5 is in a WRITE state at the end of power up
RECALL, the SRAM data is corrupted. To help avoid this
situation, a 10 Kohm resistor is connected either between WE
and system V
Software STORE
Data is transferred from the SRAM to the nonvolatile memory by
a software address sequence. The STK14C88-5 software
STORE cycle is initiated by executing sequential CE controlled
READ cycles from six specific address locations in exact order.
During the STORE cycle, an erase of the previous nonvolatile
data is first performed followed by a program of the nonvolatile
elements. When a STORE cycle is initiated, input and output are
disabled until the cycle is completed.
Because a sequence of READs from specific addresses is used
for STORE initiation, it is important that no other READ or WRITE
accesses intervene in the sequence. If they intervene, the
sequence is aborted and no STORE or RECALL takes place.
To initiate the software STORE cycle, the following READ
sequence is performed:
1. Read address 0x0E38, Valid READ
2. Read address 0x31C7, Valid READ
3. Read address 0x03E0, Valid READ
4. Read address 0x3C1F, Valid READ
5. Read address 0x303F, Valid READ
6. Read address 0x0FC0, Initiate STORE cycle
The software sequence is clocked with CE controlled READs.
When the sixth address in the sequence is entered, the STORE
cycle commences and the chip is disabled. It is important that
READ cycles and not WRITE cycles are used in the sequence.
It is not necessary that OE is LOW for a valid sequence. After the
t
STORE
READ and WRITE operation.
if HSB is used as
CAP
Software RECALL
Data is transferred from the nonvolatile memory to the SRAM by
a software address sequence. A software RECALL cycle is
. During
DELAY
initiated with a sequence of READ operations in a manner similar
to the software STORE initiation. To initiate the RECALL cycle,
DELAY
the following sequence of CE controlled READ operations is
performed:
1. Read address 0x0E38, Valid READ
2. Read address 0x31C7, Valid READ
3. Read address 0x03E0, Valid READ
4. Read address 0x3C1F, Valid READ
5. Read address 0x303F, Valid READ
6. Read address 0x0C63, Initiate RECALL cycle
Internally, RECALL is a two step procedure. First, the SRAM data
is cleared, and then the nonvolatile information is transferred into
<
the SRAM cells. After the t
CC
again ready for READ and WRITE operations. The RECALL
CC
, a RECALL
operation does not alter the data in the nonvolatile elements. The
SWITCH
nonvolatile data can be recalled an unlimited number of times.
to complete.
HRECALL
or between CE and system V
CC
cycle time is fulfilled, the SRAM is again activated for
cycle time, the SRAM is once
RECALL
STK14C88-5
.
CC
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