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5.6TMS320C24xxGuidelines
5.6.1General
TMS320 DSP Standard Algorithms vs. DCS Modules The C24xx family of DSPs
are classified as DSP controllers, and consequently are mainly focused on the “Digital
Control Space.” From an algorithm standpoint, the control space is characterized by
systems built up from many smaller and reusable software blocks or modules; e.g.,
PID controllers, coordinate transformations, trigonometric transformations, signal
generators, etc. In addition, the C24xx DSP controllers are offered in numerous
memory configurations, with lower cost devices having 4k words of program memory.
This imposes some restrictions on how much overhead can be wrapped on each one
of these smaller modules when creating it’s interface, or API.
In order to address the mentioned sensitivities within the control space, the Digital
Control Systems group (DCS) at TI has created smaller and reusable blocks of
modular software known as DCS modules. These modules are not
eXpressDSP-compliant algorithm; however, they provide the benefit of allowing
software designers to use them in order to quickly and efficiently build up standard
algorithms without jeopardizing the algorithm’s compliance to the standard.
Please refer to the application note, SPRA701, A Software Modularity Strategy for
Digital Control Systems, for further information on DCS modules.
5.6.2DataModels
5.6.3ProgramModels
5.6.4RegisterConventions
TMS320C24xxGuidelines
ThissectiondescribestherulesandguidelinesthatarespecifictotheTMS320C24xxfamilyofdigital
signalprocessors(DSPs).Notethat24xxherereferstothefollowingDSPs:C240,C241,C242,C243,
andC240x.
AsperallothereXpressDSP-compliantalgorithms,C24xxeXpressDSP-compliantalgorithms(also
referredtoasDCSComponents)mustalsofullyadheretotherulesandguidelinesasdescribedwithin
thisdocumentandtheTMS320DSPAlgorithmStandardAPIReference.
TheC24xxhasjustonedatamodel,sotherearenospecialdatamemoryrequirementsforthisprocessor.
TheC24xxCcompilersupportsonlytheonestandard64Kwordreachprogrammodel,sothereareno
specialprogrammemoryrequirementsforthisprocessor.
ThissectiondescribestherulesandguidelinesthatapplytotheuseoftheTMS320C24xxon-chip
registers.Asdescribedpreviously,thereareseveraldifferentregistertypes.Notethatanyregisterthatis
notdescribedheremustnotbeaccessedbyanalgorithm;e.g.,IFR,IMR,statusandcontrolregisters
(SCSR1,SCSR2,WSGR),andperipheralcontrolregisters.Thetablebelowdescribesalloftheregisters
thatmaybeaccessedbyanalgorithm.
RegisterUseType
AR0CcompilerFramepointerPreserve(local)
AR1CcompilerStackpointerPreserve
AR2CcompilerLocalvariablepointerScratch(local)
AR2-AR5CcompilerExpressionanalysisScratch(local)
SPRU352G–June2005–RevisedFebruary2007DSP-SpecificGuidelines57
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