CY14B256Q3 Просмотр технического описания (PDF) - Cypress Semiconductor
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CY14B256Q3 Datasheet PDF : 26 Pages
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CY14B256Q1
CY14B256Q2
CY14B256Q3
Device Operation
CY14B256Q1/CY14B256Q2/CY14B256Q3 is a 256-Kbit
nvSRAM memory with a nonvolatile element in each memory
cell. All the reads and writes to nvSRAM happen to the SRAM
which gives nvSRAM the unique capability to handle infinite
writes to the memory. The data in SRAM is secured by a STORE
sequence that transfers the data in parallel to the nonvolatile
QuantumTrap cells. A small capacitor (VCAP) is used to
AutoStore the SRAM data in nonvolatile cells when power goes
down providing power-down data security. The QuantumTrap
nonvolatile elements built in the reliable SONOS technology
make nvSRAM the ideal choice for secure data storage.
The 256-Kbit memory array is organized as 32 K words × 8 bits.
The memory is accessed through a standard SPI interface that
enables very high clock speeds up to 40 MHz with zero cycle
delay read and write cycles. This device supports SPI modes 0
and 3 (CPOL, CPHA = 0, 0 and 1, 1) and operates as SPI slave.
The device is enabled using the chip select (CS) pin and
accessed through serial input (SI), serial output (SO), and serial
clock (SCK) pins.
This device provides the feature for hardware and software write
protection through the WP pin and WRDI instruction respectively
along with mechanisms for block write protection (one quarter,
one half, or full array) using BP0 and BP1 pins in the Status
Register. Further, the HOLD pin is used to suspend any serial
communication without resetting the serial sequence.
CY14B256Q1/CY14B256Q2/CY14B256Q3 uses the standard
SPI opcodes for memory access. In addition to the general SPI
instructions for read and write, it provides four special
instructions which enable access to four nvSRAM specific
functions: STORE, RECALL, AutoStore Disable (ASDISB), and
AutoStore Enable (ASENB).
The major benefit of nvSRAM over serial EEPROMs is that all
reads and writes to nvSRAM are performed at the speed of SPI
bus with zero cycle delay. Therefore, no wait time is required
after any of the memory accesses. The STORE and RECALL
operations need finite time to complete and all memory accesses
are inhibited during this time. While a STORE or RECALL
operation is in progress, the busy status of the device is indicated
by the Hardware STORE Busy (HSB) pin and also reflected on
the RDY bit of the Status Register.
The device is available in three different pin configurations that
enable the user to choose a part which fits in best in their
application. The feature summary is given in Table 1.
Table 1. Feature Summary
Feature
WP
VCAP
HSB
AutoStore
Power-Up
RECALL
Hardware
STORE
Software
STORE
Software
RECALL
CY14B256Q1 CY14B256Q2 CY14B256Q3
Yes
No
Yes
No
Yes
Yes
No
No
Yes
No
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
SRAM Write
All writes to nvSRAM are carried out on the SRAM and do not
use up any endurance cycles of the nonvolatile memory. This
enables user to perform infinite write operations. A write cycle is
performed through the WRITE instruction. The WRITE
instruction is issued through the SI pin of the nvSRAM and
consists of the WRITE opcode, two bytes of address, and one
byte of data. Write to nvSRAM is done at SPI bus speed with zero
cycle delay.
The device allows burst mode writes to be performed through
SPI. This enables write operations on consecutive addresses
without issuing a new WRITE instruction. When the last address
in memory is reached in burst mode, the address rolls over to
0x0000 and the device continues to write.
The SPI write cycle sequence is defined in the Memory Access
section of SPI Protocol Description.
SRAM Read
A read cycle is performed at the SPI bus speed and the data is
read out with zero cycle delay after the READ instruction is
executed. The READ instruction is issued through the SI pin of
the nvSRAM and consists of the READ opcode and two bytes of
address. The data is read out on the SO pin.
This device allows burst mode reads to be performed through
SPI. This enables reads on consecutive addresses without
issuing a new READ instruction. When the last address in
memory is reached in burst mode read, the address rolls over to
0x0000 and the device continues to read.
The SPI read cycle sequence is defined explicitly in the Memory
Access section of SPI Protocol Description.
Document Number: 001-53882 Rev. *E
Page 3 of 26
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