Nios® V Processor Software Developer Handbook

ID 743810
Date 10/06/2025
Public
Document Table of Contents

9.2.2. CLINT-Vectored Mode

Different from CLINT-Direct, CLINT-Vectored enables the processor to work with a dedicated interrupt vector for every interrupt.
  • Interrupts are handled separately from hardware exceptions. Each interrupt has its own dedicated vector, tied to its ISRs. Interrupt vectors are calculated from the base address of the vector table and the interrupt cause number.
  • Hardware exceptions are handled the same as with CLINT-Direct. All exceptions are handled by an exception dispatcher residing at a single location - the base address of the vector table.
When the Nios® V processor is under CLINT-Vectored mode, it implements a simple, vectored interrupt controller. Upon receipt of a trap (interrupt or exception) request, the Nios® V processor:
  1. If it is an exception, jumps to the exception vector, which is stored in mtvec CSR.
  2. If it is an interrupt, jumps to the individual interrupt vector, which is specific for each interrupt.
  3. Allows interrupt handler to mask other interrupts.
The CLINT-Vectored carries out the role of dispatching handler (identifies the trap cause and dispatches the registered ISR). Thus, a simpler trap handling system is implemented under CLINT-Vectored. A total of 16 independent platform interrupt signals are available in CLINT-Vectored.
Table 42.  Supported Traps
Type of Traps List of Traps
Interrupt
  • Machine software interrupt
  • Machine timer interrupt
  • 16 Platform interrupt
Exception
  • Instruction address misaligned
  • Instruction access fault
  • Illegal Instruction
  • Breakpoint
  • Load address misaligned
  • Load access fault
  • Store address misaligned
  • Store access fault
  • Hardware Error