IDT72421/72201/72211/72221/72231/72241/72251 CMOS SyncFIFO™
64 x 9, 256 x 9, 512 x 9, 1,024 x 9, 2,048 x 9, 4,096 x 9 and 8,192 x 9
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
OUTPUTS:
FULL FLAG (FF)
The Full Flag (FF) will go LOW, inhibiting further write operation, when the
device is full. If no reads are performed after Reset (RS), the Full Flag (FF)
will go LOW after 64 writes for the IDT72421, 256 writes for the IDT72201, 512
writes for the IDT72211, 1,024 writes for the IDT72221, 2,048 writes for the
IDT72231, 4,096 writes for the IDT72241, and 8,192 writes for the IDT72251.
The Full Flag (FF) is synchronized with respect to the LOW-to-HIGH
transition of the Write Clock (WCLK).
EMPTY FLAG (EF)
The Empty Flag (EF) will go LOW, inhibiting further read operations, when
the read pointer is equal to the write pointer, indicating the device is empty.
The Empty Flag (EF) is synchronized with respect to the LOW-to-HIGH
transition of the Read Clock (RCLK).
PROGRAMMABLE ALMOST-FULL FLAG (PAF)
The Programmable Almost-Full flag (PAF) will go LOW when the FIFO
reaches the almost-full condition. If no reads are performed after Reset (RS),
the Programmable Almost-Full flag (PAF) will go LOW after (64-m) writes for the
IDT72421, (256-m) writes for the IDT72201, (512-m) writes for the IDT72211,
(1,024-m) writes for the IDT72221, (2,048-m) writes for the IDT72231, (4,096-
m) writes for the IDT72241, and (8,192-m) writes for the IDT72251. The offset
“m” is defined in the Full offset registers.
If there is no Full offset specified, the Programmable Almost-Full flag (PAF)
will go LOW at Full-7 words.
The Programmable Almost-Full flag (PAF) is synchronized with respect to
the LOW-to-HIGH transition of the Write Clock (WCLK).
PROGRAMMABLE ALMOST-EMPTY FLAG (PAE)
The Programmable Almost-Empty flag (PAE) will go LOW when the read
pointer is "n+1" locations less than the write pointer. The offset "n" is defined
in the Empty Offset registers. If no reads are performed after Reset the
Programmable Almost-Empty flag (PAE) will go HIGH after "n+1" for the
IDT72421/72201/72211/72221/72231/72241/72251.
If there is no Empty offset specified, the Programmable Almost-Empty flag
(PAE) will go LOW at Empty+7 words.
The Programmable Almost-Empty flag (PAE) is synchronized with respect
to the LOW-to-HIGH transition of the Read Clock (RCLK).
DATA OUTPUTS (Q
0
- Q
8
)
Data outputs for a 9-bit wide data.
TABLE 1 — STATUS FLAGS
IDT72421
0
1 to n
(1)
(n+1) to (64-(m+1))
(64-m)
(2)
to 63
64
NUMBER OF WORDS IN FIFO
IDT72201
0
1 to n
(1)
(n+1) to (256-(m+1))
(256-m)
(2)
to 255
256
IDT72211
0
1 to n
(1)
(n+1) to (512-(m+1))
(512-m)
(2)
to 511
512
FF
H
H
H
H
L
PAF
H
H
H
L
L
PAE
L
L
H
H
H
EF
L
H
H
H
H
NUMBER OF WORDS IN FIFO
IDT72221
0
1 to n
(1)
(n+1) to (1,024-(m+1))
(1,024-m)
(2)
to 1,023
1,024
NOTES:
1. n = Empty Offset (n = 7 default value)
2. m = Full Offset (m = 7 default value)
IDT72231
0
1 to n
(1)
(n+1) to (2,048-(m+1))
(2,048-m)
(2)
to 2,047
2,048
IDT72241
0
1 to n
(1)
(n+1) to (4,096-(m+1))
(4,096-m)
(2)
to 4,095
4,096
IDT72251
0
1 to n
(1)
(n+1) to (8,192-(m+1))
(8,192-m)
(2)
to 8,191
8,192
FF
H
H
H
H
L
PAF
H
H
H
L
L
PAE
L
L
H
H
H
EF
L
H
H
H
H
7
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
