10

COMMERCIAL,INDUSTRIALANDMILITARY

TEMPERATURERANGES

IDT7201L/7201LA/7202LA CMOS ASYNCHRONOUS FIFO

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

U SAGE M ODES:

WIDTH EXPANSION

Word width may be increased simply by connecting the corresponding

input control signals of multiple devices. Status flags (EF, FF and HF) can be

detected from any one device. Figure 13 demonstrates an 18-bit word width

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),

the FIFO permits a reading of a single word after writing one word of data into

edge of W, called the first write edge, and it remains on the bus until the R line

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. The RlinecausestheFFtobedeassertedbuttheWlinebeingLOW

causes it to be asserted again in anticipation of a new data word. On the rising

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