10

COMMERCIAL,INDUSTRIALANDMILITARY

TEMPERATURERANGES

IDT7203/7204/7205/7206/7207/7208 CMOS ASYNCHRONOUS FIFO

2,048 x 9, 4,096 x 9, 8,192 x 9, 16,384 x 9, 32,768 x 9, 65,536 x 9

IDT

7203

7204

7205

7206

7207

7208

XI

XI

9

18

9

WRITE (

W)

FULL FLAG (

FF)

RESET (

RS)

99

18

HF

HF

DATA

(D)

IN

READ (

R)

EMPTY FLAG (

EF)

RETRANSMIT (

RT)

DATA

(Q)

OUT

IDT

7203

7204

7205

7206

7207

7208

2661 drw15

USAGE MODES:

Width Expansion

Wordwidthmaybeincreasedsimplybyconnectingthecorrespondinginput

controlsignalsofmultipledevices. Statusflags(

EF,FFandHF)canbedetected

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

two IDT7203/7204/7205/7206/7207/7208s. Any word width can be attained

by adding additional IDT7203/7204/7205/7206/7207/7208s (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

IDT7203/7204/7205/7206/7207/7208s 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

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

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

asinglewordofdataimmediatelyafterreadingonewordofdatafromafullFIFO.

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).

NOTE:

1. Flag detection is accomplished by monitoring the

FF, EF and HF signals on either (any) device used in the width expansion configuration.

Do not connect any output signals together.

Figure 12. Block Diagram of 2,048 x 9, 4,096 x 9, 8,192 x 9, 16,384 x 9, 32,768 x 9, 65,536 x 9 FIFO Used in Single Device 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

7203

7204

7205

7206

7207

7208

(HALF-FULL FLAG)

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Figure 13. Block Diagram of 2,048 x 18, 4,096 x 18, 8,192 x 18, 16,384 x 18, 32,768 x 18, 65,536 x 18 FIFO Memory Used in Width Expansion Mode