
64K/128K x 9 Deep Sync FIFOs
CY7C4281
CY7C4291
Cypress Semiconductor Corporation
Document #: 38-06007 Rev. *B
3901 North First Street
San Jose
,
CA 95134
408-943-2600
Revised August 19, 2003
Features
High-speed, low-power, first-in first-out (FIFO)
memories
64K × 9 (CY7C4281)
128K × 9 (CY7C4291)
0.5-micron CMOS for optimum speed/power
High-speed 100-MHz operation (10-ns read/write cycle
times)
Low power
—I
CC
= 40 mA
—
I
SB
= 2 mA
Fully asynchronous and simultaneous read and write
operation
Empty, Full, and programmable Almost Empty and
Almost Full status flags
TTL compatible
Output Enable (OE
)
pin
Independent read and write enable pins
Center power and ground pins for reduced noise
Supports free-running 50% duty cycle clock inputs
Width Expansion Capability
32-pin PLCC
Pin-compatible density upgrade to CY7C42X1
family
Pin-compatible density upgrade to
IDT72201/11/21/31/41/51
Functional Description
The CY7C4281/91 are high-speed, low-power FIFO
memories with clocked read and write interfaces. All are nine
bits wide. The CY7C4281/91 are pin-compatible to the
CY7C42X1 Synchronous FIFO family. 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, multiprocessor inter-
faces, and communications buffering.
These FIFOs have nine-bit input and output ports that are
controlled by separate clock and enable signals. The input port
is controlled by a free-running clock (WCLK) and two
write-enable pins (WEN1, WEN2/LD).
When WEN1 is LOW and WEN2/LD is HIGH, data is written
into the FIFO on the rising edge of the WCLK signal. While
WEN1, WEN2/LD is held active, data is continually written into
the FIFO on each WCLK cycle. The output port is controlled in
a similar manner by a free-running read clock (RCLK) and two
read enable pins (REN1, REN2). In addition, the
CY7C4281/91 has an output enable pin (OE). The read
(RCLK) and write (WCLK) clocks may be tied together for
single-clock operation or the two clocks may be run indepen-
dently for asynchronous read/write applications. Clock
frequencies up to 100 MHz are achievable. Depth expansion
is possible using one enable input for system control, while the
other enable is controlled by expansion logic to direct the flow
of data.
THREE-STATE
OUTPUT REGISTER
READ
CONTROL
FLAG
LOGIC
WRITE
CONTROL
WRITE
POINTER
READ
POINTER
RESET
LOGIC
INPUT
REGISTER
FLAG
PROGRAM
REGISTER
D
0
8
RCLK
Q
0 – 8
WEN1
WCLK
RS
OE
Dual Port
RAMARRAY
64K x 9
128K x 9
WEN2/LD
REN1 REN2
EF
PAE
PAF
FF
Logic Block Diagram
Pin Configuration
PLCC
Top View
D
1
D
0
PAF
PAE
RCLK
REN2
V
CC
Q
8
Q
7
Q
6
Q
5
D
8
D
7
D
6
D
5
D
4
D
3
GND
REN1
WCLK
WEN2/LD
D
2
5
6
7
8
9
10
11
12
13
OE
4
3
2
1
31 30
32
21
22
23
24
27
26
28
29
25
14 15 16 17 18 19 20
WEN1
RS
F
Q
0
Q
1
Q
2
Q
3
Q
4
E
CY7C4281
CY7C4291