9

COMMERCIAL,INDUSTRIALANDMILITARY

TEMPERATURERANGES

IDT7201L/7201LA/7202LA CMOS ASYNCHRONOUS FIFO

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

Figure 9. Half-Full Flag Timing

Figure 10. Expansion Out

Figure 11. Expansion In

OPERAT I N G M ODES:

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). For additional information, 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 IDT7200/7201A/7202A may be used when the application

requirements are for 256/512/1,024 words or less. These devices are in a

Single Device Configuration when the Expansion In (XI) control input is

grounded (see Figure 12).

DEPTH EXPANSION

The IDT7200/7201A/7202A can easily be adapted to applications when

the requirements are for greater than 256/512/1,024 words. Figure 14

demonstrates Depth Expansion using three IDT7200/7201A/7202As. Any

depth can be attained by adding additional IDT7200/7201A/7202As. These

FIFOs operate in the Depth Expansion mode when the following conditions

are met:

1. ThefirstdevicemustbedesignatedbygroundingtheFirstLoad(FL)control

input.

2. All other devices must have FL in 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 FF or 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, refer to Tech Note 9: Cascading FIFOs or

FIFO Modules.

R

W

HF

HALF-FULL OR LESS

MORE THAN HALF-FULL

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HALF-FULL OR LESS

R

W

XO

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WRITE TO

LAST PHYSICAL

LOCATION

READ FROM

LAST PHYSICAL

LOCATION

W

R

XI

WRITE TO

FIRST PHYSICAL

LOCATION

READ FROM

FIRST PHYSICAL

LOCATION

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