Cypress CY7C1475BV33, CY7C1471BV33 Functional Overview, Single Read Accesses, Burst Read Accesses

		CY7C1471BV33
		CY7C1473BV33, CY7C1475BV33
Pin Definitions (continued)
Name	IO	Description
TDO	JTAG serial	Serial Data-Out to the JTAG Circuit. Delivers data on the negative edge of TCK. If the JTAG
	output	feature is not used, this pin must be left unconnected. This pin is not available on TQFP
	Synchronous	packages.
TDI	JTAG serial input	Serial Data-In to the JTAG Circuit. Sampled on the rising edge of TCK. If the JTAG feature is
	Synchronous	not used, this pin can be left floating or connected to VDD through a pull up resistor. This pin is
		not available on TQFP packages.
TMS	JTAG serial input	Serial Data-In to the JTAG Circuit. Sampled on the rising edge of TCK. If the JTAG feature is
	Synchronous	not used, this pin can be disconnected or connected to VDD. This pin is not available on TQFP
		packages.
TCK	JTAG	Clock Input to the JTAG Circuitry. If the JTAG feature is not used, this pin must be connected
	-Clock	to VSS. This pin is not available on TQFP packages.
NC	-	No Connects. Not internally connected to the die. 144M, 288M, 576M, and 1G are address
		expansion pins and are not internally connected to the die.

Functional Overview

The CY7C1471BV33, CY7C1473BV33, and CY7C1475BV33 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 may 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). Byte Write Select (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

■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 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, output is tri-stated immediately.

Burst Read Accesses

The CY7C1471BV33, CY7C1473BV33, and CY7C1475BV33 have an on-chip burst counter that enables the user 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 the Single Read Access section. 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 wrap 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.

Document #: 001-15029 Rev. *B Page 9 of 32

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