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
COMMERCIALANDINDUSTRIAL
TEMPERATURERANGES
(1,024-m)writesfortheIDT72221,(2,048-m)writesfortheIDT72231,(4,096-
m)writesfortheIDT72241,and(8,192-m)writesfortheIDT72251. Theoffset
“m”isdefinedintheFulloffsetregisters.
IfthereisnoFulloffsetspecified,theProgrammableAlmost-Fullflag(PAF)
will go LOW at Full-7 words.
OUTPUTS:
FULL FLAG (FF)
TheFullFlag(FF)willgoLOW,inhibitingfurtherwriteoperation,whenthe
device is full. If no reads are performed after Reset (RS), the Full Flag (FF)
willgoLOWafter64writesfortheIDT72421,256writesfortheIDT72201,512
writes for the IDT72211, 1,024 writes for the IDT72221, 2,048 writes for the
IDT72231,4,096writesfortheIDT72241,and8,192writesfortheIDT72251.
The Full Flag (FF) is synchronized with respect to the LOW-to-HIGH
transitionoftheWriteClock(WCLK).
TheProgrammableAlmost-Fullflag(PAF)issynchronizedwithrespectto
theLOW-to-HIGHtransitionoftheWriteClock(WCLK).
PROGRAMMABLEALMOST-EMPTYFLAG(PAE)
TheProgrammableAlmost-Emptyflag(PAE)willgoLOWwhentheread
pointeris"n+1"locationslessthanthewritepointer. Theoffset"n"isdefined
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.
IfthereisnoEmptyoffsetspecified,theProgrammableAlmost-Emptyflag
(PAE)willgoLOWatEmpty+7words.
EMPTY FLAG (EF)
TheEmptyFlag(EF)willgoLOW,inhibitingfurtherreadoperations,when
thereadpointerisequaltothewritepointer,indicatingthedeviceisempty.
The Empty Flag (EF) is synchronized with respect to the LOW-to-HIGH
transitionoftheReadClock(RCLK).
TheProgrammableAlmost-Emptyflag(PAE)issynchronizedwithrespect
totheLOW-to-HIGHtransitionoftheReadClock(RCLK).
PROGRAMMABLE ALMOST-FULL FLAG (PAF)
The Programmable Almost-Full flag (PAF) will go LOW when the FIFO
reachesthealmost-fullcondition.IfnoreadsareperformedafterReset(RS),
theProgrammableAlmost-Fullflag(PAF)willgoLOWafter(64-m)writesforthe
IDT72421,(256-m)writesfortheIDT72201,(512-m)writesfortheIDT72211,
DATA OUTPUTS (Q0 - Q8)
Dataoutputsfora9-bitwidedata.
TABLE 1 — STATUS FLAGS
NUMBER OF WORDS IN FIFO
IDT72421
0
1 to n (1)
IDT72201
IDT72211
0
1 to n (1)
FF
H
H
H
H
L
PAF
H
PAE
L
EF
L
0
1 to n (1)
H
L
H
H
H
H
(n+1)to(64-(m+1))
(64-m)(2) to63
64
(n+1)to(256-(m+1))
(256-m)(2) to255
256
(n+1)to(512-(m+1))
(512-m)(2) to511
512
H
H
L
H
L
H
NUMBER OF WORDS IN FIFO
IDT72221
IDT72231
IDT72241
IDT72251
FF
PAF
PAE
EF
0
0
0
0
H
H
L
L
1ton(1)
1ton(1)
1ton(1)
1ton(1)
H
H
H
H
L
H
H
(n+1)to(1,024-(m+1))
(n+1)to(2,048-(m+1))
(n+1)to(4,096-(m+1))
(n+1)to(8,192-(m+1))
H
(1,024-m)(2) to1,023
(2,048-m)(2) to2,047
2,048
(4,096-m)(2) to4,095
4,096
(8,192-m)(2) to8,191
8,192
H
L
L
L
H
H
H
H
1,024
NOTES:
1. n = Empty Offset (n = 7 default value)
2. m = Full Offset (m = 7 default value)
7
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
