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COMMERCIAL,INDUSTRIALANDMILITARY

TEMPERATURERANGES

IDT7201L/7201LA/7202LA CMOS ASYNCHRONOUS FIFO

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

Device Mode, this pin acts as the retransmit input. The Single Device Mode is

initiated by grounding the Expansion In (XI).

The IDT7200/7201A/7202A can be made to retransmit data when the

RetransmitEnablecontrol(RT)inputispulsedLOW. Aretransmitoperationwill

settheinternalreadpointertothefirstlocationandwillnotaffectthewritepointer.

Read Enable (R) and Write Enable (W) must be in the HIGH state during

retransmit. This feature is useful when less than 256/512/1,024 writes are

performed between resets. The retransmit feature is not compatible with the

Depth Expansion Mode and will affect the Half-Full Flag (HF), depending on

the relative locations of the read and write pointers.

EXPANSION IN (XI)

This input is a dual-purpose pin. Expansion In (XI) is grounded to indicate

an operation in the single device mode. Expansion In (XI) is connected to

Expansion Out (XO) of the previous device in the Depth Expansion or Daisy

Chain Mode.

OU T PU T S:

FULL FLAG (FF)

The Full Flag (FF) will go LOW, inhibiting further write operation, when the

write pointer is one location less than the read pointer, indicating that the

device is full. If the read pointer is not moved after Reset (RS), the Full-Flag

(FF)willgoLOWafter256writesforIDT7200,512writesfortheIDT7201Aand

1,024 writes for the IDT7202A.

EMPTY FLAG (EF)

The Empty Flag (EF) will go LOW, inhibiting further read operations, when

the read pointer is equal to the write pointer, indicating that the device is

empty.

EXPANSION OUT/HALF-FULL FLAG (XO/HF)

This is a dual-purpose output. In the single device mode, when

Expansion In (XI) is grounded, this output acts as an indication of a half-full

memory.

After half of the memory is filled and at the falling edge of the next write

operation, the Half-Full Flag (HF) will be set LOW and will remain set until the

difference between the write pointer and read pointer is less than or equal

to one half of the total memory of the device. The Half-Full Flag (HF) is then

reset by using rising edge of the read operation.

IntheDepthExpansionMode,ExpansionIn(XI)isconnectedtoExpansion

Out (XO) of the previous device. This output acts as a signal to the next device

in the Daisy Chain by providing a pulse to the next device when the previous

device reaches the last location of memory.

Dataoutputsfor9-bitwidedata. Thisdataisinahighimpedancecondition

whenever Read (R) is in a HIGH state.

SI GN AL DESCRI PT I ON S

I N PU T S:

Data inputs for 9-bit wide data.

CON T ROLS:

RESET (RS)

Reset is accomplished whenever the Reset (RS) input is taken to a LOW

state. During reset, both internal read and write pointers are set to the first

location. A reset is required after power up before a write operation can take

place. Both the Read Enable (R) and Write Enable (W) inputs must be

the rising edge of RS. Half-Full Flag (HF) will be reset to HIGH after

Reset (RS).

WRITE ENABLE (W)

A write cycle is initiated on the falling edge of this input if the Full Flag (FF)

isnotset. Dataset-upandholdtimesmustbeadheredtowithrespecttotherising

edgeoftheWriteEnable(W). DataisstoredintheRAMarraysequentiallyand

independently of any on-going read operation.

After half of the memory is filled and at the falling edge of the next write

operation,theHalf-FullFlag(HF)willbesettoLOWandwillremainsetuntilthe

difference between the write pointer and read pointer is less than or equal to

onehalfofthetotalmemoryofthedevice. TheHalf-FullFlag(HF)isthenreset

by the rising edge of the read operation.

To prevent data overflow, the Full Flag (FF) will go LOW, inhibiting further

write operations. Upon the completion of a valid read operation, the Full

isfull,theinternalwritepointerisblockedfrom W,soexternalchangesinWwill

not affect the FIFO when it is full.

READ ENABLE (R)

AreadcycleisinitiatedonthefallingedgeoftheReadEnable(R)provided

theEmptyFlag(EF)isnotset. ThedataisaccessedonaFirst-In/First-Outbasis,

independent of any ongoing write operations. After Read Enable (R) goes

thenextReadoperation. WhenalldatahasbeenreadfromtheFIFO,theEmpty

Flag (EF) will go LOW, allowing the “final” read cycle but inhibiting further read

operations with the data outputs remaining in a high impedance state. Once a

validwriteoperationhasbeenaccomplished,theEmptyFlag(EF)willgoHIGH

readpointerisblockedfromR soexternalchangesin RwillnotaffecttheFIFO

when it is empty.

FIRST LOAD/RETRANSMIT (FL/RT)

This is a dual-purpose input. In the Depth Expansion Mode, this pin is

groundedtoindicatethatitisthefirstloaded(seeOperatingModes). IntheSingle