IDT7201L/7201LA/7202LACMOSASYNCHRONOUSFIFO
256 x 9, 512 x 9 and 1,024 x 9
COMMERCIAL,INDUSTRIALANDMILITARY
TEMPERATURERANGES
theFIFOpermitsareadingofasinglewordafterwritingonewordofdatainto
anemptyFIFO. Thedataisenabledonthebusin(tWEF +tA)nsaftertherising
edgeofW,calledthefirstwriteedge,anditremainsonthebusuntiltheRline
israisedfromLOW-to-HIGH, afterwhichthebuswouldgointoathree-state
mode after tRHZ ns. The EF line would have a pulse showing temporary
deassertionandthenwouldbeasserted.
In the write flow-through mode (Figure 18), the FIFO permits the writing
of a single word of data immediately after reading one word of data from a
fullFIFO. TheRlinecausestheFFtobedeassertedbuttheWlinebeingLOW
causesittobeassertedagaininanticipationofanewdataword. Ontherising
edge of W, the new word is loaded in the FIFO. The W line must be toggled
whenFFisnotassertedtowritenewdataintheFIFOandtoincrementthewrite
pointer.
USAGEMODES:
WIDTH EXPANSION
Word width may be increased simply by connecting the corresponding
inputcontrolsignalsofmultipledevices. Statusflags(EF,FFandHF)canbe
detectedfromanyonedevice. Figure13demonstratesan18-bitwordwidth
by using two IDT7200/7201A/7202As. Any word width can be attained by
adding additional IDT7200/7201A/7202As (Figure 13).
BIDIRECTIONAL OPERATION
Applications which require data buffering between two systems (each
system capable of Read and Write operations) can be achieved by pairing
IDT7200/7201A/7202AsasshowninFigure16.BothDepthExpansionand
Width Expansion may be used in this mode.
COMPOUND EXPANSION
Thetwoexpansiontechniquesdescribedabovecanbeappliedtogether
in a straightforward manner to achieve large FIFO arrays (see Figure 15).
DATA FLOW-THROUGH
Two types of flow-through modes are permitted, a read flow-through
and write flow-through mode. For the read flow-through mode (Figure 17),
(HALF-FULL FLAG)
WRITE (W)
(HF)
READ (R)
9
9
IDT
DATA OUT (Q)
DATA IN (D)
FULL FLAG (FF)
RESET (RS)
7200/
7201A/
7202A
EMPTY FLAG (EF)
RETRANSMIT (RT)
EXPANSION IN (XI)
2679 drw 14
Figure 12. Block Diagram of Single 256 x 9, 512 x 9, 1,024 x 9 FIFO
HF
HF
18
9
9
IN
DATA (D)
IDT
WRITE (W)
FULL FLAG (FF)
RESET (RS)
READ (R)
7200/
7201A/
7202A
IDT
EMPTY FLAG (EF)
7200/
7201A/
7202A
RETRANSMIT (RT)
9
9
XI
XI
18
DATA OUT (Q)
2679 drw 15
Figure 13. Block Diagram of 256 x 18, 512 x 18, 1,024 x 18 FIFO Memory Used in Width Expansion Mode
10