Nios® V Processor Software Developer Handbook

ID 743810
Date 4/07/2025
Public
Document Table of Contents

9.3.4.1.1. Exception Cause Codes

Table 45.   Nios® V Processor Exception Cause Codes
Exception Cause Code Cause Symbol2 Possible Cause
Instruction address misaligned 0 NIOSV_INSTRUCTION_ADDRESS_MISALIGNED
  • Incorrect jump or branch
  • Corrupted instruction stream
  • Faulty loader or linker
  • Hardware issues
  • Pointer errors
  • Compiler error
Instruction access fault 1 NIOSV_INSTRUCTION_ACCESS_FAULT Unlikely to happen because Nios® V processor does not support Physical Memory Protection (PMP).
Illegal instruction 2 NIOSV_ILLEGAL_INSTRUCTION
  • Corrupted code
  • Unsupported instruction
  • Jump to incorrect address
  • Linker error
  • Memory issues
  • Assembler/Compiler error
  • Programming error
Breakpoint 3 NIOSV_BREAKPOINT
  • Debugging
  • Breakpoint instruction
  • Watchpoint or Conditional breakpoint
  • Software-Trigged breakpoint
Load address misaligned 4 NIOSV_LOAD_ADDRESS_MISALIGNED
  • Pointer misuse
  • Data structure misalignment
  • Programming error
  • Compiler/Assembler error
Load access fault 5 NIOSV_LOAD_ACCESS_FAULT Unlikely to happen because Nios® V processor does not support Physical Memory Protection (PMP).
Store/AMO address misaligned 6 NIOSV_STORE_AMO_ADDRESS_MISALIGNED
  • Pointer misuse
  • Data structure misalignment
  • Incorrect memory mapping
  • Programming error
  • Compiler/Assembler error
Store/AMO access fault 7 NIOSV_STORE_AMO_ACCESS_FAULT Unlikely to happen because Nios® V processor does not support Physical Memory Protection (PMP).
Environment call from U-mode 8 NIOSV_ENVIRONMENT_CALL_FROM_U_MODE Unlikely to happen because Nios® V processor does not support User mode.
Environment call from S-mode 9 NIOSV_ENVIRONMENT_CALL_FROM_S_MODE Unlikely to happen because Nios® V processor does not support Supervisor mode.
Reserved 10 NIOSV_RESERVED_BIT_10
Environment call from M-mode 11 NIOSV_ENVIRONMENT_CALL_FROM_M_MODE
  • Custom system calls
  • Signaling an event
Instruction page fault 12 NIOSV_INSTRUCTION_PAGE_FAULT Unlikely to happen because Nios® V processor does not support virtual memory.
Load page fault 13 NIOSV_LOAD_PAGE_FAULT Unlikely to happen because Nios® V processor does not support virtual memory.
Reserved 14 NIOSV_RESERVED_BIT_14
Store/AMO page fault 15 NIOSV_STORE_AMO_PAGE_FAULT Unlikely to happen because Nios® V processor does not support virtual memory.
Hardware error 19 NIOSV_ECC_EXCEPTION ECC error in processor’s memory blocks.
Cause unknown3 -1 NIOSV_UNDEFINED_CAUSE
Note: It is possible for an instruction-related exception to occur during execution of an ISR.
2 Cause symbols are defined in sys/alt_exceptions.h.
3 This value is passed to the instruction-related exception handler if the cause argument if the cause is not known.