9

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 and 65,536 x 9

APRIL 3, 2006

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

onthedevicewhere

Risused).ForadditionalinformationontheIDT7203/7204/

7205/7206/7207, refer to Tech Note 8: Operating FIFOs on Full and Empty

Boundary Conditions and Tech Note 6: Designing with FIFOs.

Single Device Mode

A single IDT7203/7204/7205/7206/7207/7208 may be used when the

applicationrequirementsarefor2,048/4,096/8,192/16,384/32,768/65,536words

or less. These FIFOs are in a Single Device Configuration when the Expansion

In (

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

Depth Expansion

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

ments are for greater than 2,048/4,096/8,192/16,384/32,768/65,536 words.

Figure 14 demonstrates Depth Expansion using three IDT7203/7204/7205/

7206/7207/7208s. Any depth can be attained by adding additional IDT7203/

7204/7205/7206/7207/7208s. ThesedevicesoperateintheDepthExpansion

mode when the following conditions are met:

1. ThefirstdevicemustbedesignatedbygroundingtheFirstLoad(

FL)control

input.

2. All other devices must have

FLin the HIGH state.

3. The Expansion Out (

XO)pinofeachdevicemustbetiedtotheExpansion

In (

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

4. External logic is needed to generate a composite Full Flag (

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. The Retransmit (

RT) function and Half-Full Flag (HF) are not available in

the Depth Expansion Mode.

For additional information on the IDT7203/7204/7205/7206/7207, refer to

Tech Note 9: Cascading FIFOs or FIFO Modules.

W

R

HF

HALF-FULL OR LESS

MORE THAN HALF-FULL

HALF-FULL OR LESS

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W

R

XO

WRITE TO

LAST PHYSICAL

LOCATION

READ FROM

LAST PHYSICAL

LOCATION

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W

R

XI

WRITE TO

FIRST PHYSICAL

LOCATION

READ FROM

FIRST PHYSICAL

LOCATION

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