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

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

onthedevicewhereRisused).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-

mentsareforgreaterthan2,048/4,096/8,192/16,384/32,768/65,536words.

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

7206/7207/7208s. AnydepthcanbeattainedbyaddingadditionalIDT7203/

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

modewhenthefollowingconditionsaremet:

1. ThefirstdevicemustbedesignatedbygroundingtheFirstLoad(FL)control

input.

2. All other devices 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. 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

tRHF

tWHF

2661 drw11

W

R

XO

WRITE TO

LAST PHYSICAL

LOCATION

tXOL

tXOH

READ FROM

LAST PHYSICAL

LOCATION

2661 drw12

tXOH

tXOL

W

R

XI

WRITE TO

FIRST PHYSICAL

LOCATION

READ FROM

FIRST PHYSICAL

LOCATION

tXI

tXIR

2661 drw13

tXIS

tXIS