Design of Fast Interrupt Controller for RISC-V Processor

Abstract

This work presents a Core Local Interrupt Controller (CLIC) for the RISC-V processor that achieves low-latency and efficient interrupt handling. By combining Selective Hardware Vectoring (SHV), a priority-aware arbitration tree, and a kill-ack handshake, the design services interrupts in 1–3 clock cycles, reducing latency by 50% over CLINT and 80% over PLIC. Simulation and APB configuration results validate its accuracy, flexibility, and suitability for real-time and safety-critical applications.

Introduction: For current processors to handle numerous asynchronous events with prompt CPU reaction, an interrupt controller is necessary. This study introduces a Core Local Interrupt Controller (CLIC) that uses a priority-aware arbitration tree and hardware vectoring to handle interrupts quickly and reliably. Selective Hardware Vectoring (SHV) with a kill-ack handshake allow for real-time preemption by removing software-managed handlers and servicing interrupts (IDs 32, 42, and 52) in three clock cycles. According to simulation studies, latency is reduced by 50% over CLINT and 80% over PLIC, confirming a constant three-cycle response. Functional accuracy was confirmed by APB activity during configuration, which makes the suggested CLIC perfect for latency-sensitive, real-time applications.

Objectives: The primary objective of this work is to design an efficient Core Local Interrupt Controller (CLIC) for the RISC-V processor. The proposed design is simulated and validated in Xilinx Vivado, with waveform analysis used to ensure functional accuracy. The focus is on minimizing interrupt response time by reducing the number of clock cycles required for servicing, thereby achieving lower interrupt latency and enhancing real-time performance for latency-critical applications.

Methods: The Core Local Interrupt Controller (CLIC) was designed and implemented using SystemVerilog and validated through Xilinx Vivado 2023.2 simulation. The design incorporated a priority-aware arbitration tree, hardware vectoring, and a kill-ack handshake mechanism to minimize interrupt response time and ensure real-time preemption. A dedicated testbench environment was developed to evaluate functional accuracy. Multiple interrupt sources (IDs 32, 42, and 52) with varying priorities were applied to validate arbitration accuracy and latency. Key signals, including irq_valid, irq_id, irq_level, irq_priv, and handshake signals, were monitored in waveforms to confirm proper sequencing and reliable register interactions over the APB interface.

Performance evaluation focused on measuring clock cycles from interrupt trigger to handler initiation, with comparisons against baseline controllers like CLINT and PLIC. Results consistently demonstrated reduced latency, validating the efficiency and reliability of the proposed architecture.

Results: According to simulation studies, the suggested CLIC design consistently reduces latency by about 50% over CLINT and 80% over PLIC by servicing interrupts within 1–3 clock cycles. In order to provide precise and predictable interrupt handling, waveform analysis confirmed appropriate arbitration, hardware vectoring, and dependable APB register access.

Conclusions: The proposed CLIC design significantly reduces interrupt response time and latency, demonstrating superior performance over CLINT and PLIC, making it well-suited for real-time and latency-sensitive applications.