. LSI Logic - Index of

SN54LS222, SN54LS224, SN54LS227, SN54LS228SN74LS222, SN74LS224, SN74LS227, SN74LS22816 X 4 SYNCHRONOUS FIRST·IN FIRST·OUT MEMORIESJANUARY 1981 REVISED MARCH 1985• Independent Synchonous Inputs andOutputs• 16 Words of 4 Bits Each• 3·State Outputs Drive Bus Lines Directly• Data Rates from 0 to 10 MHz• Fall·Through Time ... 50 ns Typ• Data Terminals Arranged for Optimum PCBoard Layout• Expandable Using External GatingdescriptionThese 64-bit memories are Low-Power Schottkymemory arrays organized as 16 words of 4 bitseach. They can be expanded in multiples of15m + 1 words or 4n bits, or both, (where n isthe number of packages in the vertical array andm is the number of packages in the horizontalarray) however some external gating is required(see Figure 1). For longer words using the'LS224 or 'LS228, the IR signals of the first-rankpackages and OR signals of the last-rankpackages must be ANDed for propersynchronization.TYPEoperationINPUT-READY ENABLE ANDOUTPUT-READY ENABLEOUTPUT'LS222 Yes 3·State'LS22"4 No 3-State'LS227 Yes Open·collector'LS228 No Open-collectorSN54LS222. SN54LS227 ... J PACKAGESN74LS222. SN74LS227 ... J OR N PACKAGE(TOP VIEW)OEVCCIREUNCKIRORELOCKOR00 00NCNC01 0102 0203 03GNOCLRSN54LS224. SN54LS228 ... J PACKAGESN74LS224. SN74LS228 ... J OR N PACKAGE(TOP VIEW)OEVCCIRUNCKLOCKOR00 0001 0102 02D3 03GNDCLRNC ~ No internal connectionFor chip carrier informationcontact the factory.EllCJ)Q)(J'S;Q)cen....IA FIFO memory is a storage device that allows data to be written into and read from its array at independentdata rates. These FIFOs are designed to process data at rates from 0 to 10 MHz in a bit-parallel format,word by word. Data is written into the memory on a high-to-Iow transition at the load clock input (LOCK)and read out on a low-to-high transition at the unload clock input (UNCK).The memory is full when the number of words clocked in exceeds the number of words clocked out by16. When the memory is full, LOCK signals have no effect. When the memory is empty, UNCK signalshave no effect.Status of the FIFO memory (see timing diagram) is monitored by the input ready (IR) and output ready(OR) flags that indicate "not full" and "not empty" conditions. The IR output will be high only when thememory is not full and the LOCK input is low. The OR output will be high only when the memory is notempty and UNCK is high.A low level at the clear (CLR) input resets the internal stack control counters and also sets IR high andOR low to indicate that old data remaining at the data outputs is invalid. Data outputs are non invertingwith respect to the data inputs and are at high impedance when output enable (OE) is low. OE does notaffect the IR and OR outputs.PRODUCTION DATA documents contain informationcurrent as of publication date. Products conform tospecifications per the terms of Texas Instruments~~~~~~~~i~a{~~I~'J~ ~!~:i~~ti:r ~1\O~:~:~~t~rOs~s notTEXAS -II}INSTRUMENTSPOST OFFICE BOX 225012 • DALLAS. TEXAS 75265Copyright © 1979. Texas Instruments Incorporated2-13