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5.3.4RegisterConventions
5.3.5StatusRegister
TMS320C6xxxRulesandGuidelines
Inaddition,noalgorithmmayeverdirectlymanipulatethecachecontrolregisters.Itisimportanttorealize
thateXpressDSP-compliantalgorithmsmaybeplacedinon-chipprogrammemorybythesystem
developer.Theruleabovesimplystatesthatalgorithmsmustnotrequireplacementinon-chipmemory.
ThissectiondescribestherulesandguidelinesthatapplytotheuseoftheTMS320C6xxxon-chip
registers.Asdescribedabove,thereareseveraldifferentregistertypes.Notethatanyregisterthatisnot
describedheremustnotbeaccessedbyanalgorithm.
Thetablebelowdescribesalloftheregistersthatmaybeaccessedbyanalgorithm.
RegisterUseType
AMR=0AddressmoderegisterInit(local)
A0-A9GeneralpurposeScratch(local)
A10-A14GeneralpurposePreserve(local)
A15FramepointerPreserve(local)
A16-A31C64xgeneralpurposeScratch(local)
B0-B9GeneralpurposeScratch(local)
B10-B13GeneralpurposePreserve(local)
B14DatapagepointerPreserve(local)
B15StackpointerPreserve(local)
B16-B31C64xgeneralpurposeScratch(local)
CSRControlandstatusregisterPreserve
ICRInterruptclearregisterNotaccessible(global)
IERInterruptenableregisterRead-only(global)
IFRInterruptflagregisterRead-only(global)
IRP
(1)
InterruptreturnpointerScratch(global)
ISRInterruptsetregisterNotaccessible(global)
ISTPInterruptservicetablepointerRead-only(global)
NRPNon-maskableInterruptreturnpointerRead-only(global)
PCE1ProgramcounterRead-only(local)
FADCRC67xxfloatingpointcontrolregisterPreserve(local)
FAUCRC67xxfloatingpointcontrolregisterPreserve(local)
FMCRC67xxfloatingpointcontrolregisterPreserve(local)
(1)
IRPmaybeusedasascratch-padregisterifinterruptsaredisabled.
TheC6xxxcontainsastatusregister,CSR.Thisstatusregisterisfurtherdividedintoseveraldistinct
fields.Althougheachfieldisoftenthoughtofasaseparateregister,itisnotpossibletoaccessthese
fieldsindividually.Forexample,inordertosetonefielditisnecessarytosetallfieldsinthesamestatus
register.Therefore,itisnecessarytotreatthestatusregisterswithspecialcare;ifanyfieldofastatus
registerisoftypePreserveorRead-only,theentireregistermustbetreatedasaPreserveregister,for
example.
CSRFieldUseType
SATSaturationbitScratch(local)
CPUIDIdentifiesCPURead-only(global)
RevIdIdentifiesCPUrevisionRead-only(global)
GIEGlobalinterruptenablebitRead-only(global)
PGIEPreviousGIEvalue.Read-only(global)
48DSP-SpecificGuidelinesSPRU352G–June2005–RevisedFebruary2007
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