7

COMMERCIALTEMPERATURERANGE

IDT7280/7281/7282/7283/7284/7285 5V ASYNCHRONOUS FIFO

DUAL 256 x 9, 512 x 9, 1,024 x 9, 2,048 x 9, 4,096 x 9 and 8,192 x 9

JUNE 29, 2012

Figure 9. Half-Full Flag Timing

Figure 10. Expansion Out

Figure 11. Expansion In

OPERATING MODES:

Care must be taken to assure that the appropriate flag is monitored by

eachsystem(i.e.FFismonitoredonthedevicewhereWisused;EFismonitored

on the device where R is used).

SINGLE DEVICE MODE

A single IDT7280/7281/7282/7283/7284/7285 may be used when the

applicationrequirementsarefor256/512/1,024/2,048/4,096/8,192wordsor

less. TheseFIFOsareinaSingleDeviceConfigurationwhentheExpansion

In (XI) control input is grounded (see Figure 12).

DEPTH EXPANSION

These devices can easily be adapted to applications when the require-

ments are for greater than 256/512/1,024/2,048/4,096/8,192 words. Figure

14 demonstrates a four-FIFO Depth Expansion using two IDT7280/7281/

7282/7283/7284/7285s. Any depth can be attained by adding additional

IDT7280/7281/7282/7283/7284/7285s. These FIFOs operate in the Depth

Expansionmodewhenthefollowingconditionsaremet:

1. ThefirstFIFOmustbedesignatedbygroundingtheFirstLoad(FL)control

input.

2. All other FIFOs must have FLin the HIGH state.

3. TheExpansionOut(XO)pinofeachdevicemustbetiedtotheExpansion

In (XI) pin of the next device. See Figure 14.

4. ExternallogicisneededtogenerateacompositeFullFlag(FF)andEmpty

Flag (EF). This requires the ORing of all EFs and ORing of all FFs (i.e. all

must be set to generate the correct composite FFor EF). See Figure 14.

5. TheRetransmit(RT)functionandHalf-FullFlag(HF)arenotavailablein

the Depth Expansion Mode.

R

W

HF

3208 drw 11

HALF-FULL OR LESS

MORE THAN HALF-FULL

HALF-FULL OR LESS

R

W

XO

3208 drw 12

WRITE TO

LAST PHYSICAL

LOCATION

READ FROM

LAST PHYSICAL

LOCATION

W

XI

R

3208 drw 13

WRITE TO

FIRST PHYSICAL

LOCATION

READ FROM

FIRST PHYSICAL

LOCATION