CY7C4281
CY7C4291
Document #: 38-06007 Rev. *C
Page 2 of 16
Pin Definitions
Signal Name
Description
I/O
Description
D0–8
Data Inputs
I
Data Inputs for 9-bit bus.
Q0−8
Data Outputs
O Data Outputs for 9-bit bus.
WEN1
Write Enable 1
I
The only write enable when device is configured to have programmable flags.
Data is written on a LOW-to-HIGH transition of WCLK when WEN1 is asserted and FF
is HIGH. If the FIFO is configured to have two write enables, data is written on a
LOW-to-HIGH transition of WCLK when WEN1 is LOW and WEN2/LD and FF are HIGH.
WEN2/LD
Dual Mode Pin
Write Enable 2
I
If HIGH at reset, this pin operates as a second write enable. If LOW at reset, this
pin operates as a control to write or read the programmable flag offsets. WEN1 must be
LOW and WEN2 must be HIGH to write data into the FIFO. Data will not be written into
the FIFO if the FF is LOW. If the FIFO is configured to have programmable flags,
WEN2/LD is held LOW to write or read the programmable flag offsets.
Load
REN1, REN2
Read Enable
Inputs
I
Enables the device for Read operation. Both REN1 and REN2 must be asserted to
allow a read operation.
WCLK
Write Clock
I
The rising edge clocks data into the FIFO when WEN1 is LOW and WEN2/LD is
HIGH and the FIFO is not Full. When LD is asserted, WCLK writes data into the
programmable flag-offset register.
RCLK
Read Clock
I
The rising edge clocks data out of the FIFO when REN1 and REN2 are LOW and
the FIFO is not Empty. When WEN2/LD is LOW, RCLK reads data out of the program-
mable flag-offset register.
EF
Empty Flag
O When EF is LOW, the FIFO is empty. EF is synchronized to RCLK.
FF
Full Flag
O When FF is LOW, the FIFO is full. FF is synchronized to WCLK.
PAE
Programmable
Almost Empty
O When PAE is LOW, the FIFO is almost empty based on the almost empty offset
value programmed into the FIFO. PAE is synchronized to RCLK.
PAF
Programmable
Almost Full
O When PAF is LOW, the FIFO is almost full based on the almost full offset value
programmed into the FIFO. PAF is synchronized to WCLK.
RS
Reset
I
Resets device to empty condition. A reset is required before an initial read or write
operation after power-up.
OE
Output Enable
I
When OE is LOW, the FIFO’s data outputs drive the bus to which they are
connected. If OE is HIGH, the FIFO’s outputs are in High Z (high-impedance) state.
CY7C4281
CY7C4291
Density
64k x 9
128k x 9
Package
32-pin PLCC
32-pin PLCC
Selection Guide
7C4281/91-10
7C4281/91-15
7C4281/91-25
Unit
Maximum Frequency
100
66.7
40
MHz
Maximum Access Time
8
10
15
ns
Minimum Cycle Time
10
15
25
ns
Minimum Data or Enable Set-up
3
4
6
ns
Minimum Data or Enable Hold
0.5
1
1
ns
Maximum Flag Delay
8
10
15
ns
Active Power Supply Current (ICC1)
Commercial
40
40
40
mA
Industrial
45
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