285V
CY7C4255V/CY7C4265V
CY7C4275V/CY7C4285V
32K/64Kx18 Low Voltage Deep Sync FIFOs
Features
Functional Description
The CY7C4255/65/75/85V are high-speed, low-power, first-in
• 3.3V operation for low power consumption and easy
integration into low-voltage systems
• High-speed, low-power, first-in first-out (FIFO)
memories
• 8K x 18 (CY7C4255V)
• 16K x 18 (CY7C4265V)
first-out (FIFO) memories with clocked read and write interfac-
es. All are 18 bits wide and are pin/functionally compatible to
the CY7C42X5V Synchronous FIFO family. The
CY7C4255/65/75/85V can be cascaded to increase FIFO
depth. Programmable features include Almost Full/Almost
Empty flags. These FIFOs provide solutions for a wide variety of
data buffering needs, including high-speed data acquisition, multipro-
cessor interfaces, and communications buffering.
• 32K x 18 (CY7C4275V)
• 64K x 18 (CY7C4285V)
• 0.35 micron CMOS for optimum speed/power
• High-speed 100-MHz operation (10-ns read/write cycle
times)
• Low power
— ICC = 30 mA
— ISB = 4 mA
These FIFOs have 18-bit input and output ports that are con-
trolled by separate clock and enable signals. The input port is
controlled by a free-running clock (WCLK) and a write enable
pin (WEN).
When WEN is asserted, data is written into the FIFO on the rising
edge of the WCLK signal. While WEN is held active, data is continu-
ally written into the FIFO on each cycle. The output port is controlled
in a similar manner by a free-running read clock (RCLK) and a read
enable pin (REN). In addition, the CY7C4255/65/75/85V have an
output enable pin (OE). The read and write clocks may be tied togeth-
er for single-clock operation or the two clocks may be run indepen-
dently for asynchronous read/write applications. Clock frequencies
up to 67 MHz are achievable.
• Fully asynchronous and simultaneous read and write
operation
• Empty, Full, HalfFull, andprogrammableAlmostEmpty
and Almost Full status flags
• Retransmit function
• Output Enable (OE) pin
Retransmit and Synchronous Almost Full/Almost Empty flag
features are available on these devices.
• Independent read and write enable pins
• Supports free-running 50% duty cycle clock inputs
• Width Expansion Capability
• Depth Expansion Capability
• 64-pin 10x10 STQFP
• Pin-compatible density upgrade to CY7C42X5V-ASC
families
• Pin-compatible 3.3V solutions for CY7C4255/65/75/85
Depth expansion is possible using the cascade input (WXI,
RXI), cascade output (WXO, RXO), and First Load (FL) pins. The
WXO and RXO pins are connected to the WXI and RXI pins of the
next device, and the WXO and RXO pins of the last device should be
connected to the WXI and RXI pins of the first device. The FL pin of
the first device is tied to VSS and the FL pin of all the remaining devic-
es should be tied to VCC
.
D
0 – 17
Logic Block Diagram
INPUT
REGISTER
WCLK
WEN
FLAG
PROGRAM
REGISTER
WRITE
CONTROL
High
FF
EF
Density
Dual-Port
RAM Array
FLAG
LOGIC
PAE
PAF
SMODE
8Kx9
16Kx9
32Kx9
64Kx9
WRITE
POINTER
READ
POINTER
RS
RESET
LOGIC
FL/RT
THREE-STATE
OUTPUTREGISTER
READ
CONTROL
WXI
WXO/HF
RXI
EXPANSION
LOGIC
OE
Q
0 – 17
RXO
4275V–1
RCLK
REN
Cypress Semiconductor Corporation
•
3901 North First Street
•
San Jose
•
CA 95134
•
408-943-2600
Document #: 38-06012 Rev. **
Revised September 7, 2001
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