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ARM R4F, r1p3 manual Error correction, Correct inline, Correct-and-retry

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Level One Memory System

8.2.5Error correction

When a correctable error is detected in data that has been read from a RAM, the processor has various ways of generating the correct data, which follow two schemes:

Correct inline

The error code bits are used to correct the data read from the RAM, and this data is used. This is the simplest way of correcting the data.

Correct-and-retry

The error code bits are used to correct the data, and this data is then written back to the RAM. The processor then repeats the read access by re-executing the instruction that caused the read, and reads the corrected data from the RAM if no more errors have occurred. This takes more clock cycles (at least nine) in the event of an error, but has the side-effect of correcting the data in the RAM so that the errors in the data cannot become worse.

Note

Because RAM errors generally occur infrequently, the extra cycles required to perform correct-and-retry do not have a significant impact on average performance.

The correction method that the processor uses depends on the individual error. The processor uses correct inline error correction when it detects a correctable error on a TCM read made by the AXI-slave interface. The processor uses correct-and-retry correction when it detects a correctable ECC error on a TCM read made by the instruction-side or data-side.

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ARM R4F, r1p3 manual Error correction, Correct inline, Correct-and-retry

Contents

Cortex-R4 and Cortex-R4F Technical Reference Manual Cortex-R4 and Cortex-R4FCopyright 2009 ARM Limited. All rights reserved Cortex-R4 and Cortex-R4F Technical Reference Manual Chapter IntroductionChapter Processor Initialization, Resets, and Clocking Chapter AC Characteristics Appendix B ECC Schemes List of Tables Adfsr and Aifsr bit functions Dirty register format, with ECC 11-12 Example interlocks 14-11 Table A-18 FPU signals Table C-1 List of Figures Cache operations C7 format for Set and Way Vector Catch Register format 11-20 Preface Feedback onProduct revision status Using this bookAbout this book Identifies the major revision of the productConventions TypographicalTiming diagrams SignalsARM publications Further readingThis section lists publications by ARM and by third parties Other publicationsFeedback on this product FeedbackARM welcomes feedback on this product and its documentation Feedback on this bookIntroduction About the processor About the architecture Debug on Components of the processorThis section describes the main components of the processor System control coprocessor on Interrupt handling onLoad/store unit Data Processing UnitFloating Point Unit Prefetch unitMemory Protection Unit Instruction and data cachesTCM interfaces AXI master interface Error correction and detection5 L2 AXI interfaces AXI slave interfaceETM interface DebugSystem performance monitoring Real-time debug facilitiesVIC port System control coprocessorInterrupt handling Low interrupt latencyReturn from exception using data from the stack ChangesAPB Debug interface ETM interface Test interface Processor has the following interfaces for external accessExternal interfaces of the processor APB Debug interfaceStandby mode Power managementRun mode Shutdown modeConfigurable options Configurable optionsAtcm FPU includeda BtcmVFP MPUB0TCMPCEN Configurable options at reset Feature Options RegisterAtcmpcen B1TCMPCENB1TCMECEN AtcmecenB0TCMECEN AtcmrmwNames of the pipeline stages and their functions are Execution pipeline stagesInstruction decode Execute stages First stage of data memory accessIss Write-back of data from the execution pipelinesRedundant core comparison Test features Documentation Product documentation, design flow, and architectureDesign flow Software configuration Build configurationConfiguration inputs Architectural informationAdvanced Microcontroller Bus Architecture protocol Product revision information Processor identificationVariant field, Debug ID Register Variant field, Main ID RegisterRevision field, Main ID Register Revision field, Debug ID RegisterProgram status registers on Programmer’s ModelRegisters on Exceptions onAbout the programmer’s model ARM state Switching stateInstruction set states Thumb stateOperating modes Data types Byte-invariant big-endian format Memory formatsByte-invariantbig-endian format Little-endian format Little-endian formatRegisters Register setRegister mode identifiers Mode Mode identifier General registers and program counter Program status registers N, Z, C, and V bitsQ bit IT bitsDNM bits J bitGE bits I and F bits E bitA bit Non-maskable fast interrupts onM bits PSR mode bit valuesM40 Mode Visible state registers Thumb Modification of PSR bits by MSR instructionsARM DDI 0363E Exception entry and exit summary Reset on Interrupts on Aborts onExceptions Exception entry and exit summaryTaking an exception Leaving an exceptionInterrupts ResetInterrupt request Program status registers on Non-maskable fast interrupts Fast interrupt requestNon-maskable fast interrupts Interrupt entry flowchart Interrupt controllerInterrupt entry sequence Data aborts AbortsPrefetch aborts Precise abortsImprecise aborts Aborts in Strongly Ordered and Device memoryAbort handler Supervisor call instructionUndefined instruction Breakpoint instructionException vectors Acceleration of execution environments Unaligned and mixed-endian data access support Architecture Reference ManualBig-endian instruction support Reset modes on Processor Initialization, Resets, and ClockingResets on Initialization on1 MPU InitializationCaches on TCM on 2 CRS5 TCM CachesPreloading TCMs Write to TCM directly from debugger DMA into TCMPreloading TCMs with parity or ECC Using TCMs from reset PRESETDBGn ResetsNRESET NSYSPORESETReset modes Power-on resetNormal operation Processor resetHalt operation AXI interface clocking ClockingAXI interface clocking Clock gating Clock gatingSystem Control Coprocessor About the system control coprocessor System control coprocessor functional groupsFunction Register/operation Reference to description System control coprocessor register functionsFcse PID TCM control TCM Status System control and configurationConfiguration Region System performance Performance monitoringMPU control and configuration Cache control and configurationTCM control and configuration System performance monitorSystem validation System performance monitor registersARM DDI 0363E Register allocation System control coprocessor registersRAZ Control Undefined MPU Memory Region Read/write Enable Undefined MPU Region Access Read/writeUndefined MPU Region Size Read/write NumberARM DDI 0363E Event Select Read/write Unpredictable Performance Monitor Undefined C3-c11 C12 Performance Monitor Read/writeCount Undefined RAZ,ignore C14 User Enable Read/writeUndefined C1-c15 C12 C0-c15 C13 Writes Context ID Read/write2 c0, Main ID Register 7shows the arrangement of bits in the registerMain ID Register bit functions 3 c0, Cache Type RegisterBits Field Function Cache Type Register bit functions Bits Field Function To access the Cache Type Register, read CP15 with4 c0, TCM Type Register TCM Type Register bit functions Bits Field Function5 c0, MPU Type Register To access the TCM Type Register, read CP15 withTo access the MPU Type Register, read CP15 with TCM Type Register bit functionsC0, Processor Feature Register 0, PFR0 Processor Feature Registers6 c0, Multiprocessor ID Register Processor Feature Register 0 bit functions To access the Processor Feature Register 0 read CP15 withC0, Processor Feature Register 1, PFR1 Processor Feature Register 1 bit functionsDebug Feature Register 0 bit functions To access the Processor Feature Register 1 read CP15 with8 c0, Debug Feature Register 3124 ReservedMemory Model Feature Registers To access the Debug Feature Register 0 read CP15 with9 c0, Auxiliary Feature Register C0, Memory Model Feature Register 0, MMFR0C0, Memory Model Feature Register 1, MMFR1 10 Memory Model Feature Register 0 bit functions16 Memory Model Feature Register 1 format 11 Memory Model Feature Register 1 bit functionsWFI C0, Memory Model Feature Register 2, MMFR2DMB 13 Memory Model Feature Register 3 bit functions C0, Memory Model Feature Register 3, MMFR33112 Reserved C0, Instruction Set Attributes Register 0, ISAR0 Instruction Set Attributes Registers14 Instruction Set Attributes Register 0 bit functions C0, Instruction Set Attributes Register 1, ISAR1 20 Instruction Set Attributes Register 1 formatITE C0, Instruction Set Attributes Register 2, ISAR2Indicates support for if then instructions PSR 16 Instruction Set Attributes Register 2 bit functionsIndicates support for PSR instructions 17 Instruction Set Attributes Register 3 bit functions C0, Instruction Set Attributes Register 3, ISAR3Thumb instruction sets C0, Instruction Set Attributes Register 4, ISAR4 23 Instruction Set Attributes Register 4 format12 c0, Current Cache Size Identification Register C0, Instruction Set Attributes Registers18 Instruction Set Attributes Register 4 bit functions 4KB 8KB13 c0, Current Cache Level ID Register 3130 Reserved14 c0, Cache Size Selection Register 15 c1, System Control RegisterTRE 23 System Control Register bit functionsAFE Nmfi= data caching enabled Enables L1 data cache= data caching disabled. This is the reset value = strict alignment fault checking enabledC1, Auxiliary Control Register Auxiliary Control Registers24 Auxiliary Control Register bit functions Dilsm AxiscenAxiscuen DeolpDlfo RsdisDbwr DnchC15, Secondary Auxiliary Control Register 25 Secondary Auxiliary Control Register bit functions OFC DoofmacsIXC UFCPrimary input RMWENRAM0 defines the reset value 17 c1, Coprocessor Access RegisterPrimary input RMWENRAM1 defines the reset value AtcmeccC5, Data Fault Status Register Fault Status and Address RegistersAll other encodings for these FSR bits are Reserved 28 Data Fault Status Register bit functions C5, Instruction Fault Status RegisterTo use the Dfsr read or write CP15 with There are two auxiliary fault status registers To access the Ifsr read or write CP15 withC5, Auxiliary Fault Status Registers 29 Instruction Fault Status Register bit functions= Atcm C6, Data Fault Address Register30 Adfsr and Aifsr bit functions = BtcmC6, Instruction Fault Address Register 19 c6, MPU memory region programming registersC6, MPU Region Size and Enable Registers C6, MPU Region Base Address Registers158 Sub-region disable C6, MPU Region Access Control Registers32 Region Size Register bit functions 33 MPU Region Access Control Register bit functions TEXUNP 34 Access data permission bit encodingC6, MPU Memory Region Number Register 35 MPU Memory Region Number Register bit functionsPoint of Coherency PoC Cache operationsPoint of Unification PoU Invalidate and clean operations Set and Way format36 Functional bits of c7 for Set and Way 37shows the cache sizes and the resultant bit range for SetAddress format 37 Widths of the set field for L1 cache sizes Size Set21 c9, Btcm Region Register Data Synchronization Barrier operationData Memory Barrier operation 38 Functional bits of c7 for address format Bits Field22 c9, Atcm Region Register To access the Btcm Region Register, read or write CP15 with39 Btcm Region Register bit functions 24 c11, Slave Port Control Register To access the Atcm Region Register, read or write CP15 with23 c9, TCM Selection Register 40 Atcm Region Register bit functions312 Reserved 25 c13, Fcse PID Register26 c13, Context ID Register RAZ/UNP27 c13, Thread and Process ID Registers Validation Registers C15, nVAL IRQ Enable Set RegisterCcnt overflow IRQ request C15, nVAL FIQ Enable Set Register Ccnt overflow FIQ requestC15, nVAL Debug Request Enable Set Register C15, nVAL Reset Enable Set RegisterCcnt overflow reset request C15, nVAL IRQ Enable Clear Register Ccnt overflow debug requestC15, nVAL FIQ Enable Clear Register 48 nVAL IRQ Enable Clear Register formatC15, nVAL Reset Enable Clear Register 303 Reserved UNP or SbzpC15, nVAL Debug Request Enable Clear Register 51 nVAL Debug Request Enable Clear Register format318 Reserved C15, nVAL Cache Size Override Register50 nVAL Cache Size Override Register B0000 4kB B0001 8kB B0011 16kB B0111 32kB B1111 64kBCorrectable Fault Location Register 53 Correctable Fault Location Register cache52 Correctable Fault Location Register cache C15, Build Options 1 Register To access the Build Options 1 Register, write CP15 withBuild Options Registers C15, Build Options 2 RegisterNodcache 55 Build Options 2 RegisterNoicache AtcmesNofpu BtcmesNoie NompuDcachees To access the Build Options 2 Register, write CP15 withNoharderrorcach AxibusparityPrefetch Unit About the prefetch unit Branch prediction Disabling program flow predictionBranch predictor Configuring the branch predictorIncorrect predictions and correction Return stack Events and Performance Monitor Event bus interface bit functions Bit position Update ValueAbout the events EventETMEXTOUT0 ETMEXTOUT1But with different attributes Dual issue case a branch Non-cacheable access on AXI master busInstruction cache access Dual issue case B1, B2, F2 load/store, F2DTCM correctable ECC error reported by load/store unit Yes TCM correctable ECC error reported by prefetch unit YesAbout the PMU 1 c9, Performance Monitor Control Register Performance monitoring registersPerformance monitoring registers are described 2shows how the bit values correspond with the Pmnc Register2 c9, Count Enable Set Register Pmnc Register bit functions3 c9, Count Enable Clear Register To access the Cntens Register, read or write CP15 withCntens Register bit functions Bits Field Function 4 c9, Overflow Flag Status Register To access the Cntenc Register, read or write CP15 withCycle counter enable clear Cntenc Register bit functions Bits Field Function5shows how the bit values correspond with the Flag Register To access the Flag Register, read or write CP15 with5 c9, Software Increment Register Swincr Register bit functions Bits Field Function To access the Swincr Register, read or write CP15 with6 c9, Performance Counter Selection Register 313 Reserved RAZ on reads, Sbzp on writes Increment Counter8 c9, Event Selection Register 7 c9, Cycle Count RegisterSEL To access the EVTSELx Register, read or write CP15 with EVTSELx Register bit functions9 c9, Performance Monitor Count Registers 10 c9, User Enable RegisterUseren Register bit functions Ccnt overflow interrupt enable 11 c9, Interrupt Enable Set Register10 Intens Register bit functions Bits Field Function Ccnt overflow interrupt enable bit 12 c9, Interrupt Enable Clear Register11 Intenc Register bit functions Bits Field Function To access the Intenc Register, read or write CP15 with Event bus interface Use of the event bus and countersMPU software-accessible registers on MPU faults onMemory Protection Unit About the MPU Default memory mapTrue Region size Memory regionsRegion base address SubregionsOverlapping regions Region access permissionsRegion attributes RegionExample of using regions that overlap Example of using subregionsBackground regions TCM regionsUsing memory types Memory typesARM DDI 0363E Region attributes TEX20, C, and B encodings Description Memory Type Shareable?Cacheable memory policies 1BBMPU interaction with memory system On page 7-2shows the default memory mapFollowing code is an example of disabling the MPU Background fault MPU faultsBackground fault Permission fault Alignment fault Permission faultMPU software-accessible registers On page 4-5shows the CP15 registers that control the MPULevel One Memory System About the L1 memory system L1 memory system block diagram Parity Bit ECC on About the error detection and correction schemesParity Bit ECC Error checking and correctionHard errors Read-Modify-WriteCorrect inline Error correctionCorrect-and-retry Classes of fault that can occur are Fault handlingFaults MPU faultsCache and TCM parity and ECC errors External faultsTCM external faults Precise and imprecise aborts Fault status informationDebug events Abort exceptionsImprecise abort exceptions Precise abort exceptionsUsage models Types of aborts Conditions Source Precise Fatal Correctable errorsAXI ARM DDI 0363E About the TCMs TCM attributes and permissionsTCM internal error detection and correction Atcm and Btcm configurationHandling TCM parity errors on Handling TCM ECC errors on Handling TCM ECC errors Handling TCM parity errorsTCM arbitration TCM initialization External TCM errorsTCM port protocol AXI slave interfaces for TCMs About the caches Store bufferStore buffer behavior Cache maintenance operationsStore buffer merging Store buffer drainingCache error detection and correction Error build optionsHandling cache parity errors Address decoder faultsCache parity error behavior Value Behavior Handling cache ECC errors Cache ECC error behavior Value BehaviorErrors on data cache write Errors on instruction cache readErrors on data cache read Errors on evictionsInvalidate all instruction cache Clean data cache by set/way Dirty RAM on Data RAM on Cache RAM organizationTag RAM Tag RAMCache sizes and tag RAM organization Tag RAM organization Dirty RAMData RAM Organization of a dirty RAM lineNonsequential read operation performed with one RAM access Data RAM sizes without parity or ECC implemented 13 Data cache RAM bits, with parity Description Following code is an example of enabling caches Cache interaction with memory systemDisabling or enabling all of the caches 15 Data cache data RAM sizes with ECC Cache size Data RAMsDisabling or enabling instruction cache Disabling or enabling error checkingDisabling or enabling data cache MCR p15 R0, c1 Write System Control Register Internal exclusive monitor Memory types and L1 memory system behavior Instruction-cache error events Error detection eventsTCM error events Data-cache error eventsARM DDI 0363E Level Two Interface About the L2 interface 1shows the AXI master interface attributes AXI master interfaceAttribute Value Comments Outstanding write accesses with the same ID Identifiers for AXI bus accessesOutstanding write/read access on different IDs Write responseArcachem and Awcachem encodings Encoding a Meaning Eviction bufferMemory attributes Aruserm and Awuserm encodingsMemory system implications for AXI accesses Strongly Ordered and Device transactions on AXI master interface transfersLinefills on Non-cacheable Ldrb Restrictions on AXI transfersStrongly Ordered and Device transactions Address20LDR or LDM that transfers one register Ldrh from Strongly Ordered or Device memory Address30LDM that transfers five registers LDM5, Strongly Ordered or Device memory Address40Strb to Strongly Ordered or Device memory Address40 Strh to Strongly Ordered or Device memory Address20STM of seven registers STR or STM of one registerFirst Wstrbm Cache line write-back eviction LinefillsNon-cacheable reads 14 Ldrh from Non-cacheable Normal memory Address20 15 LDR or LDM1 from Non-cacheable Normal memory Address20Non-cacheable or write-through writes AXI transaction splitting Normal write merging 20 AXI transaction splitting, data in two cache linesExample 9-1 Write merging ARM DDI 0363E AXI slave interface AXI slave interface for cache RAMsCache parity and ECC support TCM parity and ECC supportAXI slave control AXI slave characteristics 25 AXI slave interface attributesEnabling or disabling AXI slave accesses TCM RAM access on Cache RAM access on Accessing RAMs using the AXI slave interface26 RAM region decode AxUSERS bit One-hot RAM select 27 TCM chip-select decode Btcm ports TCM RAM accessARADDRSMSB, see Table RAM selectedMemory map when accessing the cache RAMs Cache RAM accessThis section contains the following 31 Cache data RAM bank/address decode Inputs ARADDRS1815 Data RAM access0010 Bank 0100 1000 0001 Bank 0010 0100 100034 Data format, instruction cache, with ECC 35 Data format, data cache, with ECC Data bit DescriptionTag RAM access ARM DDI 0363E Dirty RAM access 43 Dirty register format, with ECC Data bit DescriptionOther examples of accessing cache RAMs ARADDRS1815 = 4b1111Power Control About power control on Power management onAbout power control Dormant mode Run modeStandby mode Shutdown modeCommunication to the Power Management Controller Debug Debug state on Cache debug onDebug host Debug systemsDebug host Protocol converter Debug target Protocol converterMonitor debug-mode debugging About the debug unitHalting debug-mode debugging Programming the debug unitAll other state information associated with the debug unit Coprocessor registers 11.3.2 CP14 access permissionsDebug register interface Coprocessor registers summaryInstruction Mnemonic Description Offset Register Access Mnemonic Description Hex NumberMemory-mapped registers Debug memory-mapped registersMemory addresses for breakpoints and watchpoints APB port access permissions Power domainsEffects of resets on debug registers Privilege of memory access permissionOther Debug registers External debug interface access permissions RegistersLock Other registers6shows the CP14 debug register map Accessing debug registersDebug register descriptions 11.4.2 CP14 c0, Debug ID RegisterWRP Debug ID Register functionsBRP To use the Debug ROM Address Register, read CP14 c0 with To use the Debug ID Register, read CP14 c0 with11.4.3 CP14 c0, Debug ROM Address Register 11.4.4 CP14 c0, Debug Self Address Offset RegisterDebug Self Address Offset Register format Debug Self Address Offset Register functions11.4.5 CP14 c1, Debug Status and Control Register 10 Debug Status and Control Register functionsFlag is set to 1 on entry to debug state = disabled, this is the reset value Execute ARM instruction enable bitARM DTR access mode MOEData Transfer Register Vector Catch Register Watchpoint Fault Address Register12 Watchpoint Fault Address Register functions Reserved RAZSVC Instruction Transfer Register Bits Field Reset Description ValueDebug State Cache Control Register 14 Debug State Cache Control Register functions15 Debug Run Control Register functions Debug Run Control Register315 Reserved Breakpoint Value Registers Breakpoint Control Registers17 Breakpoint Control Registers functions 18 Meaning of BVR bits +0 is accessedCorresponding instruction address breakpoint BVR2220 MeaningWatchpoint Control Registers Watchpoint Value Registers19 Watchpoint Value Registers functions Bits Description 11 Watchpoint Control Registers format 20 Watchpoint Control Registers functionsAccessed Operating System Lock Status RegisterAuthentication Status Register 21 OS Lock Status Register functions= Dbgnopwrdwn is LOW. This is the reset value Device Power-down and Reset Control RegisterDevice Power-down and Reset Status Register 23 Prcr functions15 Prsr format 24 Prsr functionsManagement registers Processor ID RegistersClaim Tag Set Register Claim Registers27 Claim Tag Set Register functions Bits Field Function Claim Tag Clear Register Lock Access Register318 Reserved RAZ or Sbzp Claim tag clear Reset value is Lock Status RegisterDebug Identification Registers Device Type Register30 Device Type Register functions 33 Peripheral ID Register 0 functions 32 Fields in the Peripheral Identification RegistersField Size Description Bits Value Description36 Peripheral ID Register 3 functions 34 Peripheral ID Register 1 functions35 Peripheral ID Register 2 functions 37 Peripheral ID Register 4 functions1021 1020Component Identification Register 1022Debug events Software debug eventDebug event priority Halting debug eventBehavior of the processor on debug events Watchpoint debug eventsDebug exception Effect of debug exceptions on CP15 registers and Wfar 40shows the values in the link register after exceptionsFollowing sections describe Four CP15 registers that record abort information areAvoiding unrecoverable states Entering debug state Debug statePrivilege on 41 Read PC value after debug state entryBehavior of the PC and Cpsr in debug state 41 Read PC value after debug state entry Debug eventWriting to the Cpsr in debug state Accessing registers and memoryExecuting instructions in debug state PrivilegeEffects of debug events on processor registers Coprocessor instructionsEffect of debug state on non-invasive debug Exceptions in debug stateImprecise Data Aborts on entry and exit from debug state Precise Data abortImprecise Data Abort Leaving debug stateSets the DSCR1 core restarted flag to Cache pollution in debug state Cache debugThis section describes cache debug. It consists Cache coherency in debug stateThis section describes the miscellaneous debug signals APB signalsMiscellaneous debug signals External debug interface42 Authentication signal restrictions Dbgen a Authentication signalsChanging the authentication signals Non-invasive debug permittedIssue an Instruction Synchronization Barrier ISB instruction Using the debug functionality Example 11-1 Executing an ARM instruction through the ITRRules for accessing the DCC Debug communications channelExample 11-5shows the code for host-to-target data transfer Software access to the DCCDebugger access to the DCC Example 11-4 Target to host data transfer host endProgramming simple breakpoints and the byte address select Programming breakpoints and watchpointsThis section describes the following operations Example 11-6 Polling the DCC host endSetting a simple aligned watchpoint Example 11-7 Setting a simple breakpointSetting a simple unaligned watchpoint Example 11-8 Setting a simple aligned watchpointSingle-stepping Example 11-9 Setting a simple unaligned watchpoint45shows some examples Not requiredExample 11-10 Single-stepping off an instruction Debug state entryExample 11-11 Entering debug state Debug state exit Example 11-12 Leaving debug stateReading and writing registers through the DCC Accessing registers and memory in debug stateThis section describes the following Example 11-13 Reading an ARM registerReading the Cpsr in debug state Reading the PC in debug stateExample 11-15shows the code to read the PC Example 11-16shows the code for reading the CpsrExample 11-18shows the code for reading a byte of memory Example 11-19 Checking for an abort after memory accessReading memory Example 11-17 Writing the CpsrExample 11-20 Reading a block of bytes of memory Example 11-21 Reading a word of memoryExample 11-24 Writing registers in stall mode Example 11-22 Changing the DTR access modeExample 11-23 Reading registers in stall mode Fast register read/writeFast memory read/write Example 11-25 Reading a block of words of memoryAccessing coprocessor registers Example 11-27 Reading a coprocessor register11-70 Emulating power down Debugging systems with energy management capabilities11-72 FPU Programmer’s Model FPU functionality About the FPU programmer’s modelAbout the VFPv3-D16 architecture General-purpose registers FPU views of the register bankVFPv3 architecture describes the following system registers System registers1shows the VFP system registers in the Cortex-R4F FPU Mvfr registers are privileged access only All hardware ID information is privileged access onlyFpsid is privileged access only This is a change in VFPv3 compared to VFPv2DNM Floating-Point Status and Control Register, FpscrFpscr Register bit functions RmodeIDE RAZ Floating-Point Exception Register, FpexcLEN DNM IXE RAZ UFE OFE DZE IOE IDCDEX Media and VFP Feature Registers, MVFR0 and MVFR1Floating-Point Exception Register bit functions MVFR0 Register bit functionsMVFR1 Register bit functions Full denormal arithmetic supported for VFPFlush-to-zero mode Full-compliance mode Flush-to-zero mode Default NaN modeFull-compliance mode Default NaN modeIeee 754 standard implementation choices Compliance with the Ieee 754 standardComplete implementation of the Ieee 754 standard NaN handlingQNaN and SNaN handling ComparisonsUnderflow CDPExceptions Integration Test Registers About Integration Test Registers Software access using APB Programming and reading Integration Test RegistersItmiscout Register ItctrlItetmif Itmiscin1312 Processor integration testing1110 Using the Integration Test Registers Performing integration testingItetmif Register ETM interface Itetmif Register bit assignments Bits Name FunctionItmiscin Register Miscellaneous Inputs Itmiscout Register Miscellaneous OutputsItmiscout Register bit assignments Bits Name Function Dbgrestart Integration Mode Control Register ItctrlBits Name Function EtmextoutRAZ/SBZP Bits Access Reset value Name Function7shows the fields of the Itctrl Register IntmodeCycle Timings and Interlock Behavior Multiplies on Divide on Branches onDual issue on About cycle timings and interlock behavior Instruction execution overviewConditional instructions Following sequence where R1 is a Late Reg takes two cyclesFlag-setting instructions Definition of termsAssembler language syntax Takes two cycles because there are no register dependencies Register interlock examplesInstruction Behavior Sequence Takes three cycles because of the result latency of R1Cycle counts if destination is not PC Data processing instructionsCycle counts if destination is the PC Shifter Example interlocksRegister controlled shifts QADD, QDADD, QSUB, and Qdsub instructions Media data-processing SELResult of the USAD8 instruction Sum of Absolute Differences SADInstruction sequence Behavior USAD8 instructionMultiplies Umlals14-13 Divide 10 Branch instruction cycle timing behavior BranchesExample instruction Cycles Memory Comments All MRS instructions Mode changingProcessor state updating instructions All MSR instructions to the SpsrSingle load and store instructions 13shows the cycle timing behavior for loads to the PC13 Cycle timing behavior for loads to the PC Base register updateExample instruction Cycles Memory Result Comments Latency 14-19 Register offset, then 3-issue cycles Load and Store Double instructionsLoad and Store Multiple instructions Write-backReturn stack prediction Load Multiples, where the PC is in the register listCorrect condition prediction and correct Correct condition prediction and incorrect14-23 RFE and SRS instructions Synchronization instructions ClrexCoprocessor instructions Some instructions such as cache operations take more cyclesSVC formerly SWI Prefetch Abort Undefined InstructionMiscellaneous instructions Blocking and serializing Floating-point register transfer instructionsSerializing Not aligned Floating-point load/store instructionsBit aligned address 2,22,3 4,5Floating-point single-precision data processing instructions Floating-point double-precision data processing instructions Dual issue rules Permitted combinations on Dual issueDual issue rules Permitted combinations Dual issue First instruction Second instruction Case28 Permitted instruction combinations Multiply-accumulate instructionso Case F2stbAny single-precision CDPi, excluding Case F2DbAC Characteristics Processor timing on Processor timing parameters onProcessor timing Clock uncertainty 10% Processor timing parametersInput port timing parameters Clock uncertainty 50%4shows the input timing parameters for the AXI master port 3shows the timing parameters for the interrupt input portsClock uncertainty 60% 5shows the input timing parameters for the AXI slave port Rreadys6shows the input timing parameters for the debug input ports 7shows the input timing parameters for the ETM input portsClock uncertainty 65% 8shows the timing parameters for the test input portsClock uncertainty 40% Output ports timing parameters 11shows the timing parameters for the interrupt output ports13shows the timing parameters for the AXI slave output ports Write response channel Clock uncertainty 60%BRESPS10 16shows the timing parameters for the test output ports Clock uncertainty 45%18shows the timing parameters for the FPU output signals Fpidc15-13 Processor Signal Descriptions FPU signals on page A-23Any About the processor signal descriptionsFrom any clock Table A-1 Global signals Global signalsSignal Direction Clocking Description Table A-2 Configuration signals Configuration signalsTable A-2shows the processor configuration signals InformationTie LOW for even parity Tie High for odd parityRMWENRAM10b Interrupt signals, including VIC interface signals Table A-4 AXI master port signals for the L2 interface L2 interface signalsAXI master port Identification tag for the read address group of signals Identification tag for the write data group of signalsIdentification tag for the write response signal Protection signals provide addition information about a busTable A-6 AXI slave port signals for the L2 interface AXI master port error detection signalsTable A-5 AXI master port error detection signals AXI slave portProtection information, privileged/normal access. ARPROT0 Protection information, privileged/normal access. AWPROT0AXI specification One to 16. a four bit binary value minus one determinesStandard AXI specification AXI slave port error detection signalsATCM, one hot. AWUSERS30 signal is not part Table A-7 AXI slave port error detection signalsTable A-8shows the Atcm port signals TCM interface signalsTable A-9shows the B0TCM port signals Table A-10 B1TCM port signals Table A-10shows the B1TCM port signals= DMA Write data for B1TCM data RAM B1TCM RAM access is sequentialAddress for B1TCM data RAM Write parity or ECC code for B1TCMTable A-11shows the dual redundant core interface signals Dual core interface signalsTable A-11 Dual core interface signals Table A-13shows the debug miscellaneous signals Debug interface signalsTable A-12 Debug interface signals Input Tie-off Debug self-address offset Table A-13 Debug miscellaneous signalsInput Tie-off Debug ROM physical address valid Input Tie-off Debug self-address offset validTable A-14shows the ETM interface signals ETM interface signalsTable A-14 ETM interface signals Table A-15shows the test signals Test signalsTable A-15 Test signals Mbist signals Table A-16shows the Mbist signalsValidation signals Table A-17shows the validation signalsFPU signals Table A-18 FPU signalsECC Schemes ECC scheme selection guidelines on page B-2ECC scheme selection guidelines Clarified byte-invariant big-endian format NCPUHALT removed from timing diagram Added sectionsRevisions Clarified little-endian formatTable C-1 Differences between issue B and issue C Change LocationTable C-2 Differences between issue C and issue D No technical changesSee also Data Abort, External Abort and Prefetch Abort GlossaryAbort, and an internal or External Abort Base register write-backThat are divisible by four and two respectively See also Advanced High-performance BusSee Advanced High-performance Bus See Advanced Microcontroller Bus ArchitectureActive write transaction Active read transactionActive transfer Completed transferWrite ID capability Read ID widthRead issuing capability Write ID widthSee also Burst See also BeatSee also Word-invariant Accesses are expected to be word-alignedAccessed in parallel during a cache look-up BusSee also Dirty See also Clean See Embedded Trace Macrocell Option chosen does not affect software compatibility An instruction that is architecturally UndefinedBy individual implementations Precision and the fraction is all zerosSee Cold reset Serviced while normal program execution is suspendedSee also Halt mode Result of attempting to access invalid instruction memorySee Should Be Zero Or equal to 1 and is not restricted to being a power of twoSee Should Be One See Boundary scan chainDestination precision See Debug test access portIncrement of +2 User trap handler is executedProcessor-specific. a victim is also known as a cast out Expected behavior for an unaligned accessBit for the exception is set A processorCache terminology diagram