Document Number: 001-66680 Rev. *L Page 9 of 31
CY7C1460KV33
CY7C1460KVE33
CY7C1462KVE33
Single Write Accesses
Write accesses are initiated when the following conditions are
satisfied at clock rise:
■CEN is asserted LOW
■CE1, CE2, and CE3 are all asserted active
■The write signal WE is asserted LOW
The address presented to the address inputs is loaded into the
address register. The write signals are latched into the control
logic block.
On the subsequent clock rise, the data lines are automatically
tristated regardless of the state of the OE input signal. This
enables the external logic to present the data on DQ and DQP
(DQa,b,c,d/DQPa,b,c,d for CY7C1460KV33/CY7C1460KVE33 and
DQa,b/DQPa,b for CY7C1462KVE33). In addition, the address for
the subsequent access (read/write/deselect) is latched into the
address register (provided the appropriate control signals are
asserted).
On the next clock rise, the data presented to DQ and DQP
(DQa,b,c,d/DQPa,b,c,d for CY7C1460KV33/CY7C1460KVE33 and
DQa,b/DQPa,b for CY7C1462KVE33), or a subset for byte write
operations, see the Write Cycle Description table for details)
inputs is latched into the device and the write is complete.
The data written during the write operation is controlled by the
BW (BWa,b,c,d for CY7C1460KV33/CY7C1460KVE33 and BWa,b
for CY7C1462KVE33) signals. The
CY7C1460KV33/CY7C1460KVE33/CY7C1462KVE33 provides
byte-write capability that is described in the Write Cycle
Description table. Asserting the write enable input (WE) with the
selected byte write select (BW) input selectively writes to only the
desired bytes. Bytes not selected during a byte write operation
remains unaltered. A synchronous self timed write mechanism
has been provided to simplify the write operations. Byte write
capability has been included to simplify read/modify/write
sequences, which can be reduced to simple byte write opera-
tions.
Because the CY7C1460KV33/ CY7C1460KVE33/
CY7C1462KVE33 devices are common I/O devices, data should
not be driven into the device while the outputs are active. The
output enable (OE) can be deasserted HIGH before presenting
data to the DQ and DQP (DQa,b,c,d/DQPa,b,c,d for
CY7C1460KV33/CY7C1460KVE33 and DQa,b/DQPa,b for
CY7C1462KVE33) inputs. Doing so tristates the output drivers.
As a safety precaution, DQ and DQP (DQa,b,c,d/DQPa,b,c,d for
CY7C1460KV33/CY7C1460KVE33 and DQa,b/DQPa,b for
CY7C1462KVE33) are automatically tristated during the data
portion of a write cycle, regardless of the state of OE.
Burst Write Accesses
The CY7C1460KV33/CY7C1460KVE33/CY7C1462KVE33
devices have an on-chip burst counter that allows the user the
ability to supply a single address and conduct up to four WRITE
operations without reasserting the address inputs. ADV/LD must
be driven LOW to load the initial address, as described in the
Single Write Accesses section. When ADV/LD is driven HIGH on
the subsequent clock rise, the chip enables (CE1, CE2, and CE3)
and WE inputs are ignored and the burst counter is incremented.
The correct BW inputs (BWa,b,c,d for
CY7C1460KV33/CY7C1460KVE33 and BWa,b for
CY7C1462KVE33) must be driven in each cycle of the burst write
to write the correct bytes of data.
Sleep Mode
The ZZ input pin is an asynchronous input. Asserting ZZ places
the SRAM in a power conservation “sleep” mode. Two clock
cycles are required to enter into or exit from this “sleep” mode.
While in this mode, data integrity is guaranteed. Accesses
pending when entering the “sleep” mode are not considered valid
nor is the completion of the operation guaranteed. The device
must be deselected prior to entering the “sleep” mode. CE1, CE2,
and CE3, must remain inactive for the duration of tZZREC after the
ZZ input returns LOW.
On-Chip ECC
CY7C1460KVE33/CY7C1462KVE33 SRAMs include an on-chip
ECC algorithm that detects and corrects all single-bit memory
errors, including Soft Error Upset (SEU) events induced by
cosmic rays, alpha particles, and so on. The resulting Soft Error
Rate (SER) of these devices is anticipated to be <0.01 FITs/Mb,
a 4-order-of-magnitude improvement over comparable SRAMs
with no on-chip ECC, which typically have an SER of 200
FITs/Mb or more.To protect the internal data, ECC parity bits
(invisible to the user) are used.
The ECC algorithm does not correct multi-bit errors. However,
Cypress SRAMs are designed in such a way that a single SER
event has a very low probability of causing a multi-bit error
across any data word. The extreme rarity of multi-bit errors
results in a SER of <0.01 FITs/Mb.