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CY7C1461KV33 Datasheet(PDF) 8 Page - Cypress Semiconductor |
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CY7C1461KV33 Datasheet(HTML) 8 Page - Cypress Semiconductor |
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8 / 23 page  CY7C1461KV33 CY7C1463KV33 Document Number: 001-66681 Rev. *G Page 8 of 23 Functional Overview The CY7C1461KV33/CY7C1463KV33 are synchronous flow through burst SRAMs designed specifically to eliminate wait states during Write-Read transitions. All synchronous inputs pass through input registers controlled by the rising edge of the clock. The clock signal is qualified with the clock enable input signal (CEN). If CEN is HIGH, the clock signal is not recognized and all internal states are maintained. All synchronous operations are qualified with CEN. Maximum access delay from the clock rise (tCDV) is 6.5 ns (133 MHz device). Accesses can be initiated by asserting all three chip enables (CE1, CE2, CE3) active at the rising edge of the clock. If CEN is active LOW and ADV/LD is asserted LOW, the address presented to the device is latched. The access can either be a read or write operation, depending on the status of the write enable (WE). BWX can be used to conduct byte write operations. Write operations are qualified by the Write Enable (WE). All writes are simplified with on-chip synchronous self timed write circuitry. Three synchronous chip enables (CE1, CE2, CE3) and an asynchronous output enable (OE) simplify depth expansion. All operations (reads, writes, and deselects) are pipelined. ADV/LD must be driven LOW after the device is deselected to load a new address for the next operation. Single Read Accesses A read access is initiated when these conditions are satisfied at clock rise: ■ CEN is asserted LOW ■ CE1, CE2, and CE3 are ALL asserted active ■ The write enable input signal WE is deasserted HIGH ■ ADV/LD is asserted LOW The address presented to the address inputs is latched into the address register and presented to the memory array and control logic. The control logic determines that a read access is in progress and allows the requested data to propagate to the output buffers. The data is available within 6.5 ns (133 MHz device) provided OE is active LOW. After the first clock of the read access, the output buffers are controlled by OE and the internal control logic. OE must be driven LOW for the device to drive out the requested data. On the subsequent clock, another operation (Read/Write/Deselect) can be initiated. When the SRAM is deselected at clock rise by one of the chip enable signals, its output is tri-stated immediately. Burst Read Accesses The CY7C1461KV33/CY7C1463KV33 have an on-chip burst counter that provides the ability to supply a single address and conduct up to four reads without reasserting the address inputs. ADV/LD must be driven LOW to load a new address into the SRAM, as described in Single Read Accesses. The sequence of the burst counter is determined by the MODE input signal. A LOW input on MODE selects a linear burst mode, a HIGH selects an interleaved burst sequence. Both burst counters use A0 and A1 in the burst sequence, and wraps around when incremented sufficiently. A HIGH input on ADV/LD increments the internal burst counter regardless of the state of chip enable inputs or WE. WE is latched at the beginning of a burst cycle. Therefore, the type of access (read or write) is maintained throughout the burst sequence. Single Write Accesses Write access are initiated when the following conditions are satisfied at clock rise: (1) CEN is asserted LOW, (2) CE1, CE2, and CE3 are ALL asserted active, and (3) the write signal WE is asserted LOW. The address presented to the address bus is loaded into the address register. The write signals are latched into the control logic block. The data lines are automatically tri-stated regardless of the state of the OE input signal. This allows the external logic to present the data on DQs and DQPX. On the next clock rise the data presented to DQs and DQPX (or a subset for byte write operations, see Truth Table on page 10 for details) inputs is latched into the device and the write is complete. Additional accesses (read/write/deselect) can be initiated on this cycle. The data written during the write operation is controlled by BWX signals. The CY7C1461KV33/CY7C1463KV33 provide byte write capability that is described in the truth table. Asserting the (WE) with the selected byte write select input selectively writes to only the desired bytes. Bytes not selected during a byte write operation remains unaltered. A synchronous self timed write mechanism is provided to simplify the write operations. Byte write capability is included to greatly simplify Read/Modify/Write sequences, which can be reduced to simple byte write operations. Because the CY7C1461KV33/CY7C1463KV33 are common I/O devices, data must not be driven into the device when the outputs are active. The OE can be deasserted HIGH before presenting data to the DQs and DQPX inputs. This tri-states the output drivers. As a safety precaution, DQs and DQPX are automatically tri-stated during the data portion of a write cycle, regardless of the state of OE. NC/576M N/A Not Connected to the Die. Can be tied to any voltage level. NC/1G N/A Not Connected to the Die. Can be tied to any voltage level. Pin Definitions (continued) Pin Name I/O Description |
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