CY14B512P_12 Datasheet, PDF (5/34 Pages) Cypress Semiconductor – 512-Kbit (64 K × 8) Serial (SPI) nvSRAM with Real Time Clock

CY14B512P
Figure 2 shows the proper connection of the storage capacitor
(V_CAP) for AutoStore operation. Refer to DC Electrical
Characteristics on page 23 for the size of the V_CAP.
Figure 2. AutoStore Mode
V_CC
0.1 uF
V_CC
CS
V_CAP
V_SS
V_CAP
Software STORE Operation
Software STORE allows the user to trigger a STORE operation
through a special SPI instruction. The STORE operation is
initiated by executing a STORE instruction regardless of whether
a write has been performed since the last NV operation.
A STORE cycle takes t_STORE time to complete, during which all
the memory accesses to nvSRAM are inhibited. The RDY bit of
the Status Register or the HSB pin may be polled to find the
Ready / Busy status of the nvSRAM. After the t_STORE cycle time
is completed, the SRAM is activated again for read and write
operations.
Hardware STORE and HSB Pin Operation
The HSB pin in CY14B512P is used to control and acknowledge
STORE operations. If no STORE/RECALL is in progress, this pin
can be used to request a Hardware STORE cycle. When the
HSB pin is driven LOW, the CY14B512P conditionally initiates a
STORE operation after t_DELAY duration. A STORE cycle starts
only if a write to the SRAM was performed since the last STORE
or RECALL cycle. Reads and writes to the memory are inhibited
for t_STORE duration or as long as HSB pin is LOW.
The HSB pin also acts as an open drain driver (internal 100-k
weak pull-up resistor) that is internally driven LOW to indicate a
busy condition when the STORE (initiated by any means) is in
progress.
Note After each Hardware and Software STORE operation HSB
is driven HIGH for a short time (t_HHHD) with standard output high
current and then remains HIGH by an internal 100-k pull-up
resistor.
Note For successful last data byte STORE, a hardware store
should be initiated atleast one clock cycle after the last data bit
D0 is received.
Upon completion of the STORE operation, the nvSRAM memory
access is inhibited for t_LZHSB time after HSB pin returns HIGH.
The HSB pin must be left unconnected if not used.
RECALL Operation
A RECALL operation transfers the data stored in the nonvolatile
QuantumTrap elements to the SRAM. In CY14B512P, a
RECALL may be initiated in two ways: Hardware RECALL,
initiated on power-up; and Software RECALL, initiated by a SPI
RECALL instruction.
Internally, RECALL is a two step procedure. First, the SRAM data
is cleared. Next, the nonvolatile information is transferred into the
SRAM cells. All memory accesses are inhibited while a RECALL
cycle is in progress. The RECALL operation does not alter the
data in the nonvolatile elements.
Hardware RECALL (Power-Up)
During power-up, when V_CC crosses V_SWITCH, an automatic
RECALL sequence is initiated, which transfers the content of
nonvolatile memory on to the SRAM.
A Power-Up RECALL cycle takes t_FA time to complete and the
memory access is disabled during this time. HSB pin is used to
detect the Ready status of the device.
Software RECALL
Software RECALL allows the user to initiate a RECALL operation
to restore the content of nonvolatile memory on to the SRAM. In
CY14B512P, this can be done by issuing a RECALL instruction
in SPI.
A Software RECALL takes t_RECALL time to complete during
which all memory accesses to nvSRAM are inhibited. The
controller must provide sufficient delay for the RECALL operation
to complete before issuing any memory access instructions.
Disabling and Enabling AutoStore
If the application does not require the AutoStore feature, it can
be disabled in CY14B512P by using the ASDISB instruction. If
this is done, the nvSRAM does not perform a STORE operation
at power-down.
AutoStore can be re-enabled by using the ASENB instruction.
However, these operations are not nonvolatile and if the user
needs this setting to survive the power cycle, a STORE operation
must be performed following AutoStore Disable or Enable
operation.
Note CY14B512P comes from the factory with AutoStore
Enabled and 0x00 written in all cells.
Note If AutoStore is disabled and V_CAP is not required, then the
V_CAP pin must be left open. The V_CAP pin must never be
connected to ground. The Power-Up RECALL operation cannot
be disabled in any case.
Document Number: 001-53872 Rev. *H
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