CY14B101L
PRELIMINARY
Document #: 001-06400 Rev. *E
Page 3 of 18
Device Operation
The CY14B101L nvSRAM is made up of two functional
components paired in the same physical cell, the SRAM
memory cell and the nonvolatile QuantumTrap cell. The SRAM
memory cell operates as a standard fast static RAM. Transfer
of data can be from the SRAM to the nonvolatile cell (the
STORE operation), or from the nonvolatile cell to SRAM (the
RECALL operation). This unique architecture allows all cells
to be stored and recalled in parallel. During the STORE and
RECALL operations SRAM READ and WRITE operations are
inhibited. The CY14B101L supports infinite reads and writes
just like a typical SRAM. In addition, it provides infinite
RECALL operations from the nonvolatile cells and up to
200,000 STORE operations.
SRAM Read
The CY14B101L performs a READ cycle whenever CE and
OE are low while WE and HSB are high. The address specified
on pins A0-16 determines which of the 131,072 data bytes will
be accessed. When the READ is initiated by an address
transition, the outputs will be valid after a delay of tAA (READ
cycle 1). If the READ is initiated by CE or OE, the outputs will
be valid at tACE or at tDOE, whichever is later (READ cycle 2).
The data outputs repeatedly responds to address changes
within the tAA access time without the need for transitions on
any control input pins. It remains valid until another address
change, or until CE or OE is brought high, or WE or HSB is
brought low.
SRAM Write
A WRITE cycle is performed whenever CE and WE are low
and HSB is high. The address inputs must be stable before
entering the WRITE cycle and must remain stable until either
CE or WE goes high at the end of the cycle.
The data on the common IO pins IO0–7 will be written into the
memory if the data is valid tSD before the end of a WE
controlled WRITE or before the end of an CE controlled
WRITE. Keep the OE high during the entire WRITE cycle to
avoid data bus contention on common IO lines. If OE is left low,
internal circuitry turns off the output buffers tHZWE after WE
goes low.
AutoStore Operation
The CY14B101L stores data to nvSRAM using one of the three
storage operations. These three operations are Hardware
Store activated by HSB, Software Store activated by an
address sequence, and AutoStore on device power down.
AutoStore operation is a unique feature of QuantumTrap
technology and is enabled by default on the CY14B101L.
During normal operation, the device draws current from VCC
to charge a capacitor connected to the VCAP pin. This stored
charge will be used by the chip to perform a single STORE
operation. If the voltage on the VCC pin drops below VSWITCH,
the part automatically disconnects the VCAP pin from VCC. A
STORE operation will be initiated with power provided by the
VCAP capacitor.
Figure 1 on page 4 shows the proper connection of the storage
capacitor (VCAP) for automatic store operation. Refer to the DC
Characteristics table for the size of VCAP. The voltage on the
VCAP pin is driven to 5V by a charge pump internal to the chip.
A pull up must be placed on WE to hold it inactive during power
up.
To reduce unnecessary nonvolatile stores, AutoStore, and
Hardware Store operations will be ignored unless at least one
WRITE operation has taken place since the most recent
STORE or RECALL cycle. Software initiated STORE cycles
are performed regardless of whether a WRITE operation has
taken place. Monitor the HSB signal by the system to detect if
an AutoStore cycle is in progress.
Pin Definitions
Pin Name
IO Type
Description
A0 – A16
Input
Address Inputs used to select one of the 131,072 bytes of the nvSRAM.
DQ0 – DQ7 Input Output Bidirectional Data IO Lines. Used as input or output lines depending on operation.
WE
Input
Write Enable Input, Active LOW. When selected LOW, enables data on the IO pins to be written
to the address location latched by the falling edge of CE.
CE
Input
Chip Enable Input, Active LOW. When LOW, selects the chip. When HIGH, deselects the chip.
OE
Input
Output Enable, Active LOW. The active LOW OE input enables the data output buffers during read
cycles. IO pins are tri-stated on deasserting OE high.
VSS
Ground
Ground For The Device. Must be connected to ground of the system.
VCC
Power Supply Power Supply Inputs To The Device.
HSB
Input Output Hardware Store Busy (HSB). When low this output indicates a hardware store is in progress. When
pulled low external to the chip it initiates a nonvolatile STORE operation. A weak internal pull up
resistor keeps this pin HIGH if not connected. (connection optional)
VCAP
Power Supply Autostore Capacitor. Supplies power to nvSRAM during power loss to store data from SRAM to
nonvolatile elements.
NC
No Connect No Connect. Do not connect this pin to the die.
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