Exceptions, Exception entry and exit summary | ARM r1p3, R4F

Programmer’s Model

2.8Exceptions

Exceptions are taken whenever the normal flow of a program must temporarily halt, for example, to service an interrupt from a peripheral. Before attempting to handle an exception, the processor preserves the critical parts of the current processor state so that the original program can resume when the handler routine has finished.

This section provides information of the processor exception handling:

•Exception entry and exit summary

•Reset on page 2-18

•Interrupts on page 2-18

•Aborts on page 2-22

•Supervisor call instruction on page 2-24

•Undefined instruction on page 2-25

•Breakpoint instruction on page 2-25

•Exception vectors on page 2-26.

Note

When the processor is in debug halt state, and an exception occurs, it is handled differently to normal. See Exceptions in debug state on page 11-47for more details

2.8.1Exception entry and exit summary

Table 2-4summarizes the PC value preserved in the relevant R14 on exception entry, and the recommended instruction for exiting the exception handler.

				Table 2-4 Exception entry and exit

	Exception	Recommended return instruction	Previous state		Notes
	Exception
	or entry		ARM R14_x	Thumb R14_x
	or entry


	SVCa	MOVS PC, R14_svc	IA + 4	IA + 2	Where the IA is the
					address of the SVC or
	UNDEF	Variesb	IA + 4	IA + 2	address of the SVC or
	UNDEF	Variesb	IA + 4	IA + 2	Undefined instruction.
	PABT	SUBS PC, R14_abt, #4	IA + 4	IA + 4	Where the IA is the
					address of instruction that
					had the Prefetch Abort.

FIQ	SUBS	PC,	R14_fiq,	#4	IA + 4	IA + 4

IRQ	SUBS	PC,	R14_irq,	#4	IA + 4	IA + 4

Where the IA is the address of the instruction that was not executed because the FIQ or IRQ took priority.

DABT	SUBS PC, R14_abt, #8	IA + 8	IA + 8	Where the IA is the
				address of the Load or
				Store instruction that
				generated the Data Abort.

RESET	NA	-	-	The value saved in
				R14_svc on reset is
				Unpredictable.

BKPT	SUBS PC, R14_abt, #4	IA + 4	IA + 4	Software breakpoint.

a.	Formerly SWI.

ARM DDI 0363E	Copyright © 2009 ARM Limited. All rights reserved.	2-16
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ARM r1p3, R4F manual Exceptions, Exception entry and exit summary, Reset on Interrupts on Aborts on

Contents

Cortex-R4 and Cortex-R4F Copyright 2009 ARM Limited. All rights reserved Cortex-R4 and Cortex-R4FTechnical Reference Manual Cortex-R4 and Cortex-R4F Technical Reference Manual Chapter Introduction Chapter 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 on Product revision status Using this bookAbout this book Identifies the major revision of the product Conventions Typographical Timing diagrams Signals ARM publications Further readingThis section lists publications by ARM and by third parties Other publications Feedback on this product FeedbackARM welcomes feedback on this product and its documentation Feedback on this book Introduction 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 on Load/store unit Data Processing UnitFloating Point Unit Prefetch unit TCM interfaces Instruction and data cachesMemory Protection Unit AXI master interface Error correction and detection5 L2 AXI interfaces AXI slave interface ETM interface DebugSystem performance monitoring Real-time debug facilities VIC port System control coprocessorInterrupt handling Low interrupt latency Return from exception using data from the stack Changes APB Debug interface ETM interface Test interface Processor has the following interfaces for external accessExternal interfaces of the processor APB Debug interface Standby mode Power managementRun mode Shutdown mode Atcm Configurable optionsConfigurable options FPU includeda BtcmVFP MPU B0TCMPCEN Configurable options at reset Feature Options RegisterAtcmpcen B1TCMPCEN B1TCMECEN AtcmecenB0TCMECEN Atcmrmw Instruction decode Execution pipeline stagesNames of the pipeline stages and their functions are Execute stages First stage of data memory accessIss Write-back of data from the execution pipelines Redundant core comparison Test features Design flow Product documentation, design flow, and architectureDocumentation Software configuration Build configurationConfiguration inputs Architectural information Advanced Microcontroller Bus Architecture protocol Product revision information Processor identification Variant field, Debug ID Register Variant field, Main ID RegisterRevision field, Main ID Register Revision field, Debug ID Register Program status registers on Programmer’s ModelRegisters on Exceptions on About the programmer’s model ARM state Switching stateInstruction set states Thumb state Operating modes Data types Byte-invariant big-endian format Memory formatsByte-invariantbig-endian format Little-endian format Little-endian format Registers Register set Register mode identifiers Mode Mode identifier General registers and program counter Program status registers N, Z, C, and V bits Q bit IT bits GE bits J bitDNM bits I and F bits E bitA bit Non-maskable fast interrupts on M bits PSR mode bit valuesM40 Mode Visible state registers Thumb Modification of PSR bits by MSR instructions ARM DDI 0363E Exception entry and exit summary Reset on Interrupts on Aborts onExceptions Exception entry and exit summary Taking an exception Leaving an exception Interrupt request ResetInterrupts Non-maskable fast interrupts Fast interrupt requestProgram status registers on Non-maskable fast interrupts Interrupt entry flowchart Interrupt controller Interrupt entry sequence Data aborts AbortsPrefetch aborts Precise aborts Imprecise aborts Aborts in Strongly Ordered and Device memory Abort handler Supervisor call instruction Undefined instruction Breakpoint instruction Exception vectors Acceleration of execution environments Unaligned and mixed-endian data access support Architecture Reference Manual Big-endian instruction support Reset modes on Processor Initialization, Resets, and ClockingResets on Initialization on 1 MPU InitializationCaches on TCM on 2 CRS Preloading TCMs Caches5 TCM Preloading TCMs with parity or ECC DMA into TCMWrite to TCM directly from debugger Using TCMs from reset PRESETDBGn ResetsNRESET NSYSPORESET Reset modes Power-on reset Halt operation Processor resetNormal operation AXI interface clocking ClockingAXI interface clocking Clock gating Clock gating System Control Coprocessor About the system control coprocessor System control coprocessor functional groups Fcse PID System control coprocessor register functionsFunction Register/operation Reference to description TCM control TCM Status System control and configurationConfiguration Region System performance Performance monitoring MPU control and configuration Cache control and configuration TCM control and configuration System performance monitor System validation System performance monitor registers ARM DDI 0363E RAZ System control coprocessor registersRegister allocation Control Undefined MPU Memory Region Read/write Enable Undefined MPU Region Access Read/writeUndefined MPU Region Size Read/write Number ARM DDI 0363E Count Undefined Undefined C3-c11 C12 Performance Monitor Read/writeEvent Select Read/write Unpredictable Performance Monitor RAZ,ignore C14 User Enable Read/writeUndefined C1-c15 C12 C0-c15 C13 Writes Context ID Read/write 2 c0, Main ID Register 7shows the arrangement of bits in the register Bits Field Function 3 c0, Cache Type RegisterMain ID Register bit functions 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 Function 5 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 functions 6 c0, Multiprocessor ID Register Processor Feature RegistersC0, Processor Feature Register 0, PFR0 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 functions Debug Feature Register 0 bit functions To access the Processor Feature Register 1 read CP15 with8 c0, Debug Feature Register 3124 Reserved Memory Model Feature Registers To access the Debug Feature Register 0 read CP15 with9 c0, Auxiliary Feature Register C0, Memory Model Feature Register 0, MMFR0 C0, Memory Model Feature Register 1, MMFR1 10 Memory Model Feature Register 0 bit functions 16 Memory Model Feature Register 1 format 11 Memory Model Feature Register 1 bit functions DMB C0, Memory Model Feature Register 2, MMFR2WFI 3112 Reserved C0, Memory Model Feature Register 3, MMFR313 Memory Model Feature Register 3 bit functions 14 Instruction Set Attributes Register 0 bit functions Instruction Set Attributes RegistersC0, Instruction Set Attributes Register 0, ISAR0 C0, Instruction Set Attributes Register 1, ISAR1 20 Instruction Set Attributes Register 1 format Indicates support for if then instructions C0, Instruction Set Attributes Register 2, ISAR2ITE Indicates support for PSR instructions 16 Instruction Set Attributes Register 2 bit functionsPSR Thumb instruction sets C0, Instruction Set Attributes Register 3, ISAR317 Instruction Set Attributes Register 3 bit functions C0, Instruction Set Attributes Register 4, ISAR4 23 Instruction Set Attributes Register 4 format 18 Instruction Set Attributes Register 4 bit functions C0, Instruction Set Attributes Registers12 c0, Current Cache Size Identification Register 4KB 8KB 13 c0, Current Cache Level ID Register 3130 Reserved 14 c0, Cache Size Selection Register 15 c1, System Control Register TRE 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 enabled 24 Auxiliary Control Register bit functions Auxiliary Control RegistersC1, Auxiliary Control Register Dilsm AxiscenAxiscuen Deolp Dlfo RsdisDbwr Dnch C15, Secondary Auxiliary Control Register 25 Secondary Auxiliary Control Register bit functions OFC DoofmacsIXC UFC Primary input RMWENRAM0 defines the reset value 17 c1, Coprocessor Access RegisterPrimary input RMWENRAM1 defines the reset value Atcmecc All other encodings for these FSR bits are Reserved Fault Status and Address RegistersC5, Data Fault Status Register To use the Dfsr read or write CP15 with C5, Instruction Fault Status Register28 Data Fault Status Register bit functions 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 = Btcm C6, Instruction Fault Address Register 19 c6, MPU memory region programming registers C6, MPU Region Size and Enable Registers C6, MPU Region Base Address Registers 32 Region Size Register bit functions C6, MPU Region Access Control Registers158 Sub-region disable 33 MPU Region Access Control Register bit functions TEX UNP 34 Access data permission bit encodingC6, MPU Memory Region Number Register 35 MPU Memory Region Number Register bit functions Point of Unification PoU Cache operationsPoint of Coherency PoC Invalidate and clean operations Set and Way format 36 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 Set 21 c9, Btcm Region Register Data Synchronization Barrier operationData Memory Barrier operation 38 Functional bits of c7 for address format Bits Field 39 Btcm Region Register bit functions To access the Btcm Region Register, read or write CP15 with22 c9, Atcm Region Register 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 functions 312 Reserved 25 c13, Fcse PID Register26 c13, Context ID Register RAZ/UNP 27 c13, Thread and Process ID Registers Ccnt overflow IRQ request C15, nVAL IRQ Enable Set RegisterValidation Registers C15, nVAL FIQ Enable Set Register Ccnt overflow FIQ request Ccnt overflow reset request C15, nVAL Reset Enable Set RegisterC15, nVAL Debug Request Enable Set Register C15, nVAL IRQ Enable Clear Register Ccnt overflow debug request C15, nVAL FIQ Enable Clear Register 48 nVAL IRQ Enable Clear Register format C15, nVAL Reset Enable Clear Register 303 Reserved UNP or Sbzp C15, nVAL Debug Request Enable Clear Register 51 nVAL Debug Request Enable Clear Register format 318 Reserved C15, nVAL Cache Size Override Register50 nVAL Cache Size Override Register B0000 4kB B0001 8kB B0011 16kB B0111 32kB B1111 64kB Correctable Fault Location Register 53 Correctable Fault Location Register cache 52 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 Register Nodcache 55 Build Options 2 RegisterNoicache Atcmes Nofpu BtcmesNoie Nompu Dcachees To access the Build Options 2 Register, write CP15 withNoharderrorcach Axibusparity Prefetch Unit About the prefetch unit Branch prediction Disabling program flow prediction Incorrect predictions and correction Configuring the branch predictorBranch predictor Return stack Events and Performance Monitor Event bus interface bit functions Bit position Update ValueAbout the events Event ETMEXTOUT0 ETMEXTOUT1 But 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, F2D TCM correctable ECC error reported by load/store unit Yes TCM correctable ECC error reported by prefetch unit Yes About the PMU 1 c9, Performance Monitor Control Register Performance monitoring registersPerformance monitoring registers are described 2shows how the bit values correspond with the Pmnc Register 2 c9, Count Enable Set Register Pmnc Register bit functions Cntens Register bit functions Bits Field Function To access the Cntens Register, read or write CP15 with3 c9, Count Enable Clear Register 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 Function 5 c9, Software Increment Register To access the Flag Register, read or write CP15 with5shows how the bit values correspond with the Flag 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 Counter SEL 7 c9, Cycle Count Register8 c9, Event Selection Register To access the EVTSELx Register, read or write CP15 with EVTSELx Register bit functions Useren Register bit functions 10 c9, User Enable Register9 c9, Performance Monitor Count Registers 10 Intens Register bit functions Bits Field Function 11 c9, Interrupt Enable Set RegisterCcnt overflow interrupt enable 11 Intenc Register bit functions Bits Field Function 12 c9, Interrupt Enable Clear RegisterCcnt overflow interrupt enable bit To access the Intenc Register, read or write CP15 with Event bus interface Use of the event bus and counters Memory Protection Unit MPU faults onMPU software-accessible registers on True Default memory mapAbout the MPU Region size Memory regionsRegion base address Subregions Overlapping regions Region access permissionsRegion attributes Region Example of using regions that overlap Example of using subregions Background regions TCM regions Using memory types Memory types ARM DDI 0363E Region attributes TEX20, C, and B encodings Description Memory Type Shareable? Cacheable memory policies 1BB Following code is an example of disabling the MPU On page 7-2shows the default memory mapMPU interaction with memory system Background fault MPU faultsBackground fault Permission fault Alignment fault Permission fault MPU software-accessible registers On page 4-5shows the CP15 registers that control the MPU Level One Memory System About the L1 memory system L1 memory system block diagram Parity About the error detection and correction schemesParity Bit ECC on Bit ECC Error checking and correctionHard errors Read-Modify-Write Correct-and-retry Error correctionCorrect inline Classes of fault that can occur are Fault handlingFaults MPU faults TCM external faults External faultsCache and TCM parity and ECC errors Precise and imprecise aborts Fault status informationDebug events Abort exceptions Usage models Precise abort exceptionsImprecise abort exceptions AXI Correctable errorsTypes of aborts Conditions Source Precise Fatal ARM DDI 0363E About the TCMs TCM attributes and permissions Handling TCM parity errors on Handling TCM ECC errors on Atcm and Btcm configurationTCM internal error detection and correction TCM arbitration Handling TCM parity errorsHandling TCM ECC errors TCM port protocol External TCM errorsTCM initialization AXI slave interfaces for TCMs About the caches Store buffer Store buffer behavior Cache maintenance operationsStore buffer merging Store buffer draining Cache error detection and correction Error build options Cache parity error behavior Value Behavior Address decoder faultsHandling cache parity errors Handling cache ECC errors Cache ECC error behavior Value Behavior Errors on data cache write Errors on instruction cache readErrors on data cache read Errors on evictions Invalidate all instruction cache Clean data cache by set/way Dirty RAM on Data RAM on Cache RAM organizationTag RAM Tag RAM Cache sizes and tag RAM organization Tag RAM organization Dirty RAMData RAM Organization of a dirty RAM line Nonsequential 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 RAMs Disabling or enabling data cache Disabling or enabling error checkingDisabling or enabling instruction 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 events ARM DDI 0363E Level Two Interface About the L2 interface Attribute Value Comments AXI master interface1shows the AXI master interface attributes Outstanding write accesses with the same ID Identifiers for AXI bus accessesOutstanding write/read access on different IDs Write response Arcachem and Awcachem encodings Encoding a Meaning Eviction bufferMemory attributes Aruserm and Awuserm encodings Memory system implications for AXI accesses Linefills on AXI master interface transfersStrongly Ordered and Device transactions on Non-cacheable Ldrb Restrictions on AXI transfersStrongly Ordered and Device transactions Address20 LDR or LDM that transfers one register Ldrh from Strongly Ordered or Device memory Address30 LDM that transfers five registers LDM5, Strongly Ordered or Device memory Address40 Strb to Strongly Ordered or Device memory Address40 Strh to Strongly Ordered or Device memory Address20 First Wstrbm STR or STM of one registerSTM of seven registers Non-cacheable reads LinefillsCache line write-back eviction 14 Ldrh from Non-cacheable Normal memory Address20 15 LDR or LDM1 from Non-cacheable Normal memory Address20 Non-cacheable or write-through writes AXI transaction splitting Normal write merging 20 AXI transaction splitting, data in two cache lines Example 9-1 Write merging ARM DDI 0363E AXI slave interface AXI slave interface for cache RAMs AXI slave control TCM parity and ECC supportCache parity and ECC support AXI slave characteristics 25 AXI slave interface attributes Enabling or disabling AXI slave accesses 26 RAM region decode AxUSERS bit One-hot RAM select Accessing RAMs using the AXI slave interfaceTCM RAM access on Cache RAM access on 27 TCM chip-select decode Btcm ports TCM RAM accessARADDRSMSB, see Table RAM selected This section contains the following Cache RAM accessMemory map when accessing the cache RAMs 31 Cache data RAM bank/address decode Inputs ARADDRS1815 Data RAM access0010 Bank 0100 1000 0001 Bank 0010 0100 1000 34 Data format, instruction cache, with ECC 35 Data format, data cache, with ECC Data bit Description Tag RAM access ARM DDI 0363E Dirty RAM access 43 Dirty register format, with ECC Data bit Description Other examples of accessing cache RAMs ARADDRS1815 = 4b1111 Power Control About power control on Power management on About power control Dormant mode Run modeStandby mode Shutdown mode Communication to the Power Management Controller Debug Debug state on Cache debug on Debug host Debug systemsDebug host Protocol converter Debug target Protocol converter Monitor debug-mode debugging About the debug unitHalting debug-mode debugging Programming the debug unit All other state information associated with the debug unit Coprocessor registers 11.3.2 CP14 access permissionsDebug register interface Coprocessor registers summary Instruction Mnemonic Description Offset Register Access Mnemonic Description Hex NumberMemory-mapped registers Debug memory-mapped registers Memory addresses for breakpoints and watchpoints APB port access permissions Power domainsEffects of resets on debug registers Privilege of memory access permission Other Debug registers External debug interface access permissions RegistersLock Other registers 6shows the CP14 debug register map Accessing debug registersDebug register descriptions 11.4.2 CP14 c0, Debug ID Register BRP Debug ID Register functionsWRP 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 Register Debug Self Address Offset Register format Debug Self Address Offset Register functions 11.4.5 CP14 c1, Debug Status and Control Register 10 Debug Status and Control Register functions Flag is set to 1 on entry to debug state ARM Execute ARM instruction enable bit= disabled, this is the reset value DTR access mode MOE Data Transfer Register Vector Catch Register Watchpoint Fault Address Register12 Watchpoint Fault Address Register functions Reserved RAZ SVC Instruction Transfer Register Bits Field Reset Description ValueDebug State Cache Control Register 14 Debug State Cache Control Register functions 315 Reserved Debug Run Control Register15 Debug Run Control Register functions Breakpoint Value Registers Breakpoint Control Registers 17 Breakpoint Control Registers functions 18 Meaning of BVR bits +0 is accessedCorresponding instruction address breakpoint BVR2220 Meaning 19 Watchpoint Value Registers functions Bits Description Watchpoint Value RegistersWatchpoint Control Registers 11 Watchpoint Control Registers format 20 Watchpoint Control Registers functions Accessed Operating System Lock Status Register Authentication 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 functions 15 Prsr format 24 Prsr functions Management registers Processor ID Registers 27 Claim Tag Set Register functions Bits Field Function Claim RegistersClaim Tag Set Register Claim Tag Clear Register Lock Access Register318 Reserved RAZ or Sbzp Claim tag clear Reset value is Lock Status Register 30 Device Type Register functions Device Type RegisterDebug Identification Registers 33 Peripheral ID Register 0 functions 32 Fields in the Peripheral Identification RegistersField Size Description Bits Value Description 36 Peripheral ID Register 3 functions 34 Peripheral ID Register 1 functions35 Peripheral ID Register 2 functions 37 Peripheral ID Register 4 functions 1021 1020Component Identification Register 1022 Debug events Software debug event Debug event priority Halting debug eventBehavior of the processor on debug events Watchpoint debug events Debug 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 are Avoiding unrecoverable states Entering debug state Debug statePrivilege on 41 Read PC value after debug state entry Behavior of the PC and Cpsr in debug state 41 Read PC value after debug state entry Debug event Writing to the Cpsr in debug state Accessing registers and memoryExecuting instructions in debug state Privilege Effects of debug events on processor registers Coprocessor instructionsEffect of debug state on non-invasive debug Exceptions in debug state Imprecise Data Aborts on entry and exit from debug state Precise Data abortImprecise Data Abort Leaving debug state Sets the DSCR1 core restarted flag to Cache pollution in debug state Cache debugThis section describes cache debug. It consists Cache coherency in debug state This section describes the miscellaneous debug signals APB signalsMiscellaneous debug signals External debug interface 42 Authentication signal restrictions Dbgen a Authentication signalsChanging the authentication signals Non-invasive debug permitted Issue an Instruction Synchronization Barrier ISB instruction Using the debug functionality Example 11-1 Executing an ARM instruction through the ITR Rules for accessing the DCC Debug communications channel Example 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 end Programming simple breakpoints and the byte address select Programming breakpoints and watchpointsThis section describes the following operations Example 11-6 Polling the DCC host end Setting a simple aligned watchpoint Example 11-7 Setting a simple breakpoint Setting a simple unaligned watchpoint Example 11-8 Setting a simple aligned watchpoint Single-stepping Example 11-9 Setting a simple unaligned watchpoint45shows some examples Not required Example 11-11 Entering debug state Debug state entryExample 11-10 Single-stepping off an instruction Debug state exit Example 11-12 Leaving debug state Reading and writing registers through the DCC Accessing registers and memory in debug stateThis section describes the following Example 11-13 Reading an ARM register Reading 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 Cpsr Example 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 Cpsr Example 11-20 Reading a block of bytes of memory Example 11-21 Reading a word of memory Example 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/write Fast memory read/write Example 11-25 Reading a block of words of memory Accessing coprocessor registers Example 11-27 Reading a coprocessor register 11-70 Emulating power down Debugging systems with energy management capabilities 11-72 FPU Programmer’s Model About the VFPv3-D16 architecture About the FPU programmer’s modelFPU functionality General-purpose registers FPU views of the register bank 1shows the VFP system registers in the Cortex-R4F FPU System registersVFPv3 architecture describes the following system registers 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 VFPv2 DNM Floating-Point Status and Control Register, FpscrFpscr Register bit functions Rmode IDE RAZ Floating-Point Exception Register, FpexcLEN DNM IXE RAZ UFE OFE DZE IOE IDC DEX Media and VFP Feature Registers, MVFR0 and MVFR1Floating-Point Exception Register bit functions MVFR0 Register bit functions MVFR1 Register bit functions Full denormal arithmetic supported for VFP Flush-to-zero mode Full-compliance mode Flush-to-zero mode Default NaN modeFull-compliance mode Default NaN mode Ieee 754 standard implementation choices Compliance with the Ieee 754 standardComplete implementation of the Ieee 754 standard NaN handling QNaN and SNaN handling ComparisonsUnderflow CDP Exceptions Integration Test Registers About Integration Test Registers Software access using APB Programming and reading Integration Test Registers Itmiscout Register ItctrlItetmif Itmiscin 1110 Processor integration testing1312 Using the Integration Test Registers Performing integration testing Itetmif Register ETM interface Itetmif Register bit assignments Bits Name Function Itmiscout Register bit assignments Bits Name Function Itmiscout Register Miscellaneous OutputsItmiscin Register Miscellaneous Inputs Dbgrestart Integration Mode Control Register ItctrlBits Name Function Etmextout RAZ/SBZP Bits Access Reset value Name Function7shows the fields of the Itctrl Register Intmode Cycle Timings and Interlock Behavior Multiplies on Divide on Branches on Dual issue on About cycle timings and interlock behavior Instruction execution overview Conditional instructions Following sequence where R1 is a Late Reg takes two cyclesFlag-setting instructions Definition of terms Assembler 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 R1 Cycle counts if destination is the PC Data processing instructionsCycle counts if destination is not PC Register controlled shifts Example interlocksShifter QADD, QDADD, QSUB, and Qdsub instructions Media data-processing SEL Result of the USAD8 instruction Sum of Absolute Differences SADInstruction sequence Behavior USAD8 instruction Multiplies Umlals 14-13 Divide Example instruction Cycles Memory Comments Branches10 Branch instruction cycle timing behavior All MRS instructions Mode changingProcessor state updating instructions All MSR instructions to the Spsr Single load and store instructions 13shows the cycle timing behavior for loads to the PC Example instruction Cycles Memory Result Comments Latency Base register update13 Cycle timing behavior for loads to the PC 14-19 Register offset, then 3-issue cycles Load and Store Double instructions Load and Store Multiple instructions Write-back Return stack prediction Load Multiples, where the PC is in the register listCorrect condition prediction and correct Correct condition prediction and incorrect 14-23 RFE and SRS instructions Synchronization instructions Clrex Coprocessor instructions Some instructions such as cache operations take more cycles SVC formerly SWI Prefetch Abort Undefined Instruction Miscellaneous instructions Serializing Floating-point register transfer instructionsBlocking and serializing Not aligned Floating-point load/store instructionsBit aligned address 2,2 2,3 4,5 Floating-point single-precision data processing instructions Floating-point double-precision data processing instructions Dual issue rules Dual issueDual issue rules Permitted combinations on 28 Permitted instruction combinations Dual issue First instruction Second instruction CasePermitted combinations Multiply-accumulate instructionso Case F2stbAny single-precision CDPi, excluding Case F2Db AC Characteristics Processor timing on Processor timing parameters on Processor timing Clock uncertainty 10% Processor timing parametersInput port timing parameters Clock uncertainty 50% Clock uncertainty 60% 3shows the timing parameters for the interrupt input ports4shows the input timing parameters for the AXI master port 5shows the input timing parameters for the AXI slave port Rreadys 6shows the input timing parameters for the debug input ports 7shows the input timing parameters for the ETM input ports Clock uncertainty 40% 8shows the timing parameters for the test input portsClock uncertainty 65% Output ports timing parameters 11shows the timing parameters for the interrupt output ports 13shows 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 Fpidc 15-13 Processor Signal Descriptions FPU signals on page A-23 From any clock About the processor signal descriptionsAny Signal Direction Clocking Description Global signalsTable A-1 Global signals Table A-2 Configuration signals Configuration signalsTable A-2shows the processor configuration signals Information Tie LOW for even parity Tie High for odd parity RMWENRAM10b Interrupt signals, including VIC interface signals AXI master port L2 interface signalsTable A-4 AXI master port signals for the L2 interface 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 bus Table 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 port Protection information, privileged/normal access. ARPROT0 Protection information, privileged/normal access. AWPROT0AXI specification One to 16. a four bit binary value minus one determines Standard AXI specification AXI slave port error detection signalsATCM, one hot. AWUSERS30 signal is not part Table A-7 AXI slave port error detection signals Table A-9shows the B0TCM port signals TCM interface signalsTable A-8shows the Atcm port signals = DMA Table A-10shows the B1TCM port signalsTable A-10 B1TCM port signals Write data for B1TCM data RAM B1TCM RAM access is sequentialAddress for B1TCM data RAM Write parity or ECC code for B1TCM Table A-11 Dual core interface signals Dual core interface signalsTable A-11shows the dual redundant core interface signals Table A-12 Debug interface signals Debug interface signalsTable A-13shows the debug miscellaneous 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 valid Table A-14 ETM interface signals ETM interface signalsTable A-14shows the ETM interface signals Table A-15 Test signals Test signalsTable A-15shows the test signals Mbist signals Table A-16shows the Mbist signals Validation signals Table A-17shows the validation signals FPU signals Table A-18 FPU signals ECC Schemes ECC scheme selection guidelines on page B-2 ECC scheme selection guidelines Clarified byte-invariant big-endian format NCPUHALT removed from timing diagram Added sectionsRevisions Clarified little-endian format Table C-1 Differences between issue B and issue C Change Location Table C-2 Differences between issue C and issue D No technical changes See also Data Abort, External Abort and Prefetch Abort GlossaryAbort, and an internal or External Abort Base register write-back That are divisible by four and two respectively See also Advanced High-performance BusSee Advanced High-performance Bus See Advanced Microcontroller Bus Architecture Active write transaction Active read transactionActive transfer Completed transfer Write ID capability Read ID widthRead issuing capability Write ID width See also Burst See also Beat See also Word-invariant Accesses are expected to be word-alignedAccessed in parallel during a cache look-up Bus See 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 zeros See Cold reset Serviced while normal program execution is suspendedSee also Halt mode Result of attempting to access invalid instruction memory See Should Be Zero Or equal to 1 and is not restricted to being a power of twoSee Should Be One See Boundary scan chain Destination precision See Debug test access portIncrement of +2 User trap handler is executed Processor-specific. a victim is also known as a cast out Expected behavior for an unaligned accessBit for the exception is set A processor Cache terminology diagram