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6.5DataTransferProperties
Elem0 Elem1 Elem2 Elem3
Gaps between
elements
Element index
Frame
Element size
Frame 0
Frame 1
Frame N-1
Number of
frames = N
Frame index
6.6DataTransferSynchronization
DataTransferProperties
Somesystemsmightmapeachlogicalchanneltoaphysicalchannel,whileinothersystems,several
logicalchannelsmaptothesamephysicalchannel.Thismappingisdependentontheparticularsystem
andthenumberofavailablephysicalDMAchannels.Theimportantpointtobemadeisthatthese
variablesaretransparentfromthealgorithm'spointofviewwhenworkingwithlogicalchannels.
ThefollowingdefinitionoftransferparametersareintroducedinIDMA2todescribeaDMAtransferblock
astheunitofaDMAtransfer.EachDMAtransfercanbeseenasablockmadeupofframesand
elements.ADMAtransferisscheduledbyissuingsourceanddestinationaddressesoftheblockandthe
numberofelementsineachframe.
Thefollowingtransferparametersaresharedacrossboththesourceandthedestination:
•elementsize:thenumberofbytesperelement∈{1,2,4}forIDMA2and1≤bytes≤65535forIDMA3.
•numberofelements:thenumberofelementsperframe,1≤elements≤65535
•numberofframes:thenumberofframesintheblock,1≤frames≤65535
Thefollowingparametersmaybesharedbetweensourceanddestinationandifsupportedbyhardware,
canalsobesetindependently:
•elementindex:thesizeofthegapbetweenelementsplustheelementsizeinbytesbetweentwo
consecutiveelementswithinaframe.Zeroindicatesthatelementindexingisdisabled.
•frameindex:sizeofthegapinbytesbetweentwoconsecutiveframeswithinablock.Definedfor2D
transfersonly.
Figure6-1andFigure6-2illustratetheDMAtransfersparameters.
Figure6-1.TransferPropertiesfora1-DFrame
Figure6-2.FrameIndexand2-DTransferofN-1Frames
ADMAdatatransferisaccomplishedindependentofCPUoperations.Formaximumperformance,the
algorithmshouldschedulethoseCPUoperationsthatexecuteinparallelwiththedatatransfers,to
completeafterthedatatransfercompletes.
64UseoftheDMAResourceSPRU352G–June2005–RevisedFebruary2007
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