10

COMMERCIAL,INDUSTRIALANDMILITARY

TEMPERATURERANGES

IDT7201L/7201LA/7202LA CMOS ASYNCHRONOUS FIFO

256 x 9, 512 x 9 and 1,024 x 9

USAGE MODES:

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/7202As as shown in Figure 16. Both Depth Expansion and

Width Expansion may be used in this mode.

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),

theFIFOpermitsareadingofasinglewordafterwritingonewordofdatainto

edgeofW,calledthefirstwriteedge,anditremainsonthebusuntiltheRline

is raised from LOW-to-HIGH, after which the bus would go into a three-state

deassertion and then would be asserted.

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.

COMPOUND EXPANSION

The two expansion techniques described above can be applied together

in a straightforward manner to achieve large FIFO arrays (see Figure 15).

Figure 13. Block Diagram of 256 x 18, 512 x 18, 1,024 x 18 FIFO Memory Used in Width Expansion Mode

Figure 12. Block Diagram of Single 256 x 9, 512 x 9, 1,024 x 9 FIFO

WRITE (

W)

DATA IN (D)

FULL FLAG (

FF)

RESET (

RS)

9

READ (

R)

9

DATA OUT (Q)

EMPTY FLAG (

EF)

RETRANSMIT (

RT)

EXPANSION IN (

XI)

(

HF)

IDT

7200/

7201A/

7202A

(HALF-FULL FLAG)

2679 drw 14

IDT

7200/

7201A/

7202A

XI

XI

99

18

9

18

HF

HF

9

DATA

WRITE (

W)

FULL FLAG (

FF)

RESET (

RS)

(D)

IN

READ (

R)

EMPTY FLAG (

EF)

RETRANSMIT (

RT)

IDT

7200/

7201A/

7202A

2679 drw 15