Nios® V Embedded Processor Design Handbook

ID 726952
Date 12/09/2025
Public
Document Table of Contents

4.2.3. Signal Tap Logic Analyzer with Nios® V Processor Signal Tap Plugin

The Signal Tap logic analyzer, available in the Quartus® Prime software, captures and displays the real-time signal behaviour in an Altera FPGA design. Use the Signal Tap logic analyzer to probe and debug the behaviour of internal signals during normal device operation, without requiring extra I/O pins or external lab equipment.

The Nios® V Processor Signal Tap plugin is a debugging extension for the Signal Tap Logic Analyzer. It allows you to capture the opcodes executed by a Nios® V embedded processor. It works by creating debug nodes inside the Nios® V processor, enabling you to trigger on and capture instruction trace data that the Nios® V processor core executes. You can specify an instruction-trace trigger, which activates the Signal Tap logic analyzer when the processor reaches a specific address, symbol name, or your own Signal Tap trigger conditions.

Take note of the following Nios® V Processor Signal Tap plug-in characteristics:
  • It supports all variants of the Nios® V processor core.
  • Each plug-in instantiation is associated with a specific Nios® V processor.
  • It can operate with other Nios® V Processor SignalTap plug-in and other Signal Tap instances.
  • It automatically correlates the processor trace with a specified software image.

The Signal Tap logic analyzer can aid Nios® V processor debugging by detecting software-related problems, such as an interrupt service routine that does not properly clear the interrupt signal.