10

IDT7200/7201A/7202A CMOS ASYNCHRONOUS FIFO

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

MILITARY, INDUSTRIAL AND COMMERCIAL TEMPERATURE RANGES

USAGE MODES:

Width Expansion

Word width may be increased simply by connecting the

corresponding input control signals of multiple devices. Sta-

tus 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 an empty FIFO.

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

EF line

would have a pulse showing temporary 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 full FIFO. The

R line causes

the

FF to be deasserted but the W line being low 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 when

FF is not asserted to write new data

in the FIFO and to increment the write 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).

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)

DATA

(Q)

OUT

IDT

7200/

7201A/

7202A

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

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)

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

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