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72205LB15TFG Datasheet(PDF) 7 Page - Integrated Device Technology |
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72205LB15TFG Datasheet(HTML) 7 Page - Integrated Device Technology |
7 / 16 page 7 IDT72205LB/72215LB/72225LB/72235LB/72245LB CMOS SyncFIFOTM 256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18 COMMERCIALANDINDUSTRIAL TEMPERATURERANGES MARCH 2013 When the LD pin is LOW and WEN is HIGH, the WCLK input is disabled; thenasignalatthisinputcanneitherincrementthewriteoffsetregisterpointer, nor execute a write. Thecontentsoftheoffsetregisterscanbereadontheoutputlineswhenthe LD pin is set LOW and REN is set LOW; then, data can be read on the LOW- to-HIGH transition of the read clock (RCLK). The act of reading the control registersemploysadedicatedreadoffsetregisterpointer.(Thereadandwrite pointersoperateindependently). A read and a write should not be performed simultaneously to the offset registers. FIRST LOAD (FL) FLisgroundedtoindicateoperationintheSingleDeviceorWidthExpansion mode.IntheDepthExpansionconfiguration,FLisgroundedtoindicateitisthe first device loaded and is set to HIGH for all other devices in the Daisy Chain. (SeeOperatingConfigurationsforfurtherdetails.) WRITE EXPANSION INPUT (WXI) Thisisadualpurposepin. WXIisgroundedtoindicateoperationintheSingle Device or Width Expansion mode. WXIisconnectedtoWriteExpansionOut (WXO) of the previous device in the Daisy Chain Depth Expansion mode. READ EXPANSION INPUT (RXI) Thisisadualpurposepin.RXIisgroundedtoindicateoperationintheSingle Device or Width Expansion mode. RXI is connected to Read Expansion Out (RXO) of the previous device in the Daisy Chain Depth Expansion mode. OUTPUTS: FULL FLAG(FF) When the FIFO is full, FF will go LOW, inhibiting further write operations. WhenFFisHIGH,theFIFOisnotfull. Ifnoreadsareperformedafterareset, FFwillgoLOWafterDwritestotheFIFO. D=256writesfortheIDT72205LB, 512fortheIDT72215LB,1,024fortheIDT72225LB,2,048fortheIDT72235LB and 4,096 for the IDT72245LB. TheFFisupdatedontheLOW-to-HIGHtransitionofthewriteclock(WCLK). EMPTY FLAG/ (EF) WhentheFIFOisempty,EFwillgoLOW,inhibitingfurtherreadoperations. When EF is HIGH, the FIFO is not empty. TheEFisupdatedontheLOW-to-HIGHtransitionofthereadclock(RCLK). PROGRAMMABLE ALMOST-FULL FLAG (PAF) The Programmable Almost-Full Flag (PAF) will go LOW when FIFO reachestheAlmost-Fullcondition. IfnoreadsareperformedafterReset(RS), thePAFwillgoLOWafter(256-m)writesfortheIDT72205LB,(512-m)writes fortheIDT72215LB,(1,024-m)writesfortheIDT72225LB,(2,048–m)writes fortheIDT72235LBand(4,096–m)writesfortheIDT72245LB. Theoffset“m” isdefinedintheFULLoffsetregister. IfthereisnoFulloffsetspecified,the PAFwillbeLOWwhenthedeviceis 31awayfromcompletelyfullforIDT72205LB,63awayfromcompletelyfullfor IDT72215LB, and 127 away from completely full for IDT72225LB/72235LB/ 72245LB. ThePAFisassertedLOWontheLOW-to-HIGHtransitionofthewriteclock (WCLK).PAFisresettoHIGHontheLOW-to-HIGHtransitionofthereadclock (RCLK). Thus PAF is asynchronous. PROGRAMMABLEALMOST-EMPTYFLAG(PAE) TheProgrammableAlmost-EmptyFlag(PAE)willgoLOWwhentheread pointeris"n+1"locationslessthanthewritepointer.Theoffset"n"isdefinedin theEMPTYoffsetregister. IfthereisnoEmptyoffsetspecified,theProgrammableAlmost-EmptyFlag (PAE) will be LOW when the device is 31 away from completely empty for IDT72205LB,63awayfromcompletelyemptyforIDT72215LB,and127away fromcompletelyemptyforIDT72225LB/72235LB/72245LB. ThePAEisassertedLOWontheLOW-to-HIGHtransitionofthereadclock (RCLK).PAEisresettoHIGHontheLOW-to-HIGHtransitionofthewriteclock (WCLK). Thus PAE is asynchronous. WRITE EXPANSION OUT/HALF-FULL FLAG (WXO/HF) This is a dual-purpose output. In the Single Device and Width Expansion mode, when Write Expansion In (WXI) and Read Expansion In (RXI) are grounded,thisoutputactsasanindicationofahalf-fullmemory. Number of Words in FIFO IDT72205LB IDT72215LB IDT72225LB IDT72235LB IDT72245LB FF PAF HF PAE EF 00 0 0 0 H H H L L 1 to n(1) 1 to n(1) 1 to n(1) 1 to n(1) 1 to n(1) HH H L H (n + 1) to 128 (n + 1) to 256 (n + 1) to 512 (n + 1) to 1,024 (n + 1) to 2,048 H H H H H 129 to (256-(m+1)) 257 to (512-(m+1)) 513 to (1,024-(m+1)) 1,025 to (2,048-(m+1)) 2,049 to (4,096-(m+1)) HH L H H (256-m)(2)to255 (512-m)(2)to511 (1,024-m)(2)to1,023 (2,048-m)(2)to2,047 (4,096-m)(2)to4,095 H L L H H 256 512 1,024 2,048 4,096 L L L H H TABLE 1 — STATUS FLAGS NOTES: 1. n = Empty Offset (Default Values : IDT72205LB n=31, IDT72215LB n = 63, IDT72225LB/72235LB/72245LB n = 127) 2. m = Full Offset (Default Values : IDT72205LB m=31, IDT72215LB m = 63, IDT72225LB/72235LB/72245LB m = 127) |
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