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IDT7208L35JG Datasheet(PDF) 6 Page - Integrated Device Technology |
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IDT7208L35JG Datasheet(HTML) 6 Page - Integrated Device Technology |
6 / 14 page 6 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 loaded(seeOperatingModes).TheSingleDeviceModeisinitiatedbygrounding the Expansion In ( XI). The IDT7203/7204/7205/7206/7207/7208 can be made to retransmit data when the Retransmit Enable Control ( RT) input is pulsed LOW. A retransmit operationwillsettheinternalreadpointertothefirstlocationandwillnotaffectthe writepointer. ThestatusoftheFlagswillchangedependingontherelativelocations of the read and write pointers. Read Enable ( R) and Write Enable (W) must be intheHIGHstateduringretransmit. Thisfeatureisusefulwhenlessthan2,048/ 4,096/8,192/16,384/32,768/65,536writesareperformedbetweenresets. The retransmitfeatureisnotcompatiblewiththeDepthExpansionMode. EXPANSION IN ( XI)—Thisinputisadual-purposepin. ExpansionIn(XI) isgroundedtoindicateanoperationinthesingledevicemode. ExpansionIn( XI) isconnectedtoExpansionOut( XO)ofthepreviousdeviceintheDepthExpansion or Daisy-Chain Mode. OUTPUTS: FULL FLAG (FF )—TheFullFlag(FF)willgoLOW,inhibitingfurtherwrite operations,whenthedeviceisfull. IfthereadpointerisnotmovedafterReset( RS), the Full Flag ( FF) will go LOW after 2,048/4,096/8,192/16,384/32,768/65,536 writes. EMPTY FLAG ( EF)—TheEmptyFlag(EF)willgoLOW,inhibitingfurther readoperations,whenthereadpointerisequaltothewritepointer,indicatingthat thedeviceisempty. EXPANSIONOUT/HALF-FULLFLAG( XO/HF)—Thisisadual-purpose output. Inthesingledevicemode,whenExpansionIn( XI)isgrounded,thisoutput actsasanindicationofahalf-fullmemory. Afterhalfofthememoryisfilled,andatthefallingedgeofthenextwriteoperation, the Half-Full Flag ( HF)willbesettoLOWandwillremainsetuntilthedifference betweenthewritepointerandreadpointerislessthanorequaltoonehalfofthe totalmemoryofthedevice. TheHalf-FullFlag( HF)isthenresetbytherisingedge of the read operation. IntheDepthExpansionMode,ExpansionIn( XI)isconnectedtoExpansion Out ( XO) of the previous device. This output acts as a signal to the next device intheDaisyChainbyprovidingapulsetothenextdevicewhenthepreviousdevice reaches the last location of memory. There will be an XOpulsewhentheWrite pointerreachesthelastlocationofmemory,andanadditional XOpulsewhenthe Readpointerreachesthelastlocationofmemory. DATA OUTPUTS (Q0-Q8) — Q0-Q8 are data outputs for 9-bit wide data. Theseoutputsareinahigh-impedanceconditionwheneverRead( R)isinaHIGH state. SIGNAL DESCRIPTIONS INPUTS: DATA IN (D0–D8) — Data inputs for 9-bit wide data. CONTROLS: RESET ( RS ) — Reset is accomplished whenever the Reset (RS) input is takentoaLOWstate. Duringreset,bothinternalreadandwritepointersareset tothefirstlocation.Aresetisrequiredafterpower-upbeforeawriteoperationcan take place. Both the Read Enable ( R) and Write Enable (W) inputs must be in the HIGH state during the window shown in Figure 2 (i.e. tRSS before the rising edge of RS) and should not change until tRSR after the rising edge of RS. WRITE ENABLE ( W ) —A write cycle is initiated on the falling edge of this inputiftheFullFlag( FF)isnotset.Dataset-upandholdtimesmustbeadhered- to,withrespecttotherisingedgeoftheWriteEnable( W).DataisstoredintheRAM array sequentially and independently of any on-going read operation. Afterhalfofthememoryisfilled,andatthefallingedgeofthenextwriteoperation, theHalf-FullFlag( HF)willbesettoLOW,andwillremainsetuntilthedifference betweenthewritepointerandreadpointerisless-thanorequaltoone-halfofthe totalmemoryofthedevice.TheHalf-FullFlag( HF)isthenresetbytherisingedge of the read operation. To prevent data overflow, the Full Flag ( FF)willgoLOWonthefallingedge ofthelastwritesignal,whichinhibitsfurtherwriteoperations. Uponthecompletion of a valid read operation, the Full Flag ( FF) will go HIGH after tRFF, allowing a newvalidwritetobegin.WhentheFIFOisfull,theinternalwritepointerisblocked from W, so external changes inW will not affect the FIFO when it is full. READENABLE( R)—A readcycleisinitiatedonthefallingedgeoftheRead Enable ( R), provided the Empty Flag (EF) is not set. The data is accessed on aFirst-In/First-Outbasis,independentofanyongoingwriteoperations. AfterRead Enable ( R) goes HIGH, the Data Outputs (Q0 through Q8) will return to a high- impedanceconditionuntilthenextReadoperation. Whenallthedatahasbeen read from the FIFO, the Empty Flag ( EF) will go LOW, allowing the “final” read cyclebutinhibitingfurtherreadoperations,withthedataoutputsremaininginahigh- impedancestate.Onceavalidwriteoperationhasbeenaccomplished,theEmpty Flag ( EF) will go HIGH after tWEF and a valid Read can then begin. When the FIFOisempty,theinternalreadpointerisblockedfrom Rsoexternalchangeswill not affect the FIFO when it is empty. FIRST LOAD/RETRANSMIT ( FL/RT ) — This is a dual-purpose input. In theDepthExpansionMode,thispinisgroundedtoindicatethatitisthefirstdevice |
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