Nios® V Processor Software Developer Handbook

ID 743810
Date 5/26/2023
Public

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8.6.2.2. Exception Dispatch with the Internal Interrupt Controller

With the IIC, the general exception funnel dispatches hardware interrupts as well as software exceptions.

The general exception funnel looks at the Machine Cause (mcause) register to determine the exception type. If the Interrupt bit is set and Exception Code field is referring to hardware interrupts, the general exception funnel transfer control to the hardware interrupt funnel. Otherwise, the general exception funnel calls the appropriate timer or software interrupt handler.

The hardware interrupt funnel looks at the hardware IRQ bits in mip register. If any hardware IRQs are asserted, the interrupt funnel calls the appropriate hardware interrupt handler.

All hardware interrupts have higher priority than timer and software interrupts.

If the Interrupt bit is not set, there are no interrupts, and the exception is a software exception. In this case, the general exception funnel calls the software exception funnel.

For more information about the Nios® V processor mcause and mip registers, refer to the The RISC-V Instruction Set Manual Volume II in RISC-V International website.