FlexRIO Runtime Error –304404: Wait for IO Ready.vi Fails Due to Incorrect IO Ready Signal Naming

Updated Jan 16, 2026

Issue Details

When running an FPGA application using a FlexRIO module and custom socketed CLIP, users may encounter the runtime error –304404 from Wait for IO Ready.vi. This article describes the conditions that cause this error, expected behavior, and known workarounds. In reported cases, the issue was caused by an incorrectly named FlexRIO IO Ready signal in the FPGA project’s CLIP integration.

When this error occurs:

  • The FPGA VI runs, but host‑FPGA interaction halts where Wait for IO Ready.vi is called.
  • No additional FlexRIO module communication occurs.
  • The error is repeatable and occurs immediately at runtime.

This error is most commonly seen in:

  • FlexRIO applications that use custom socketed CLIP
  • Projects migrated between versions or modified manually
  • Bitfiles where module‑ready handshake signals were renamed or removed

 

Solution

  1. Restore or Correct the IO Ready Signal Name (Recommended)Ensure that the socketed CLIP includes a top‑level indicator named exactly:

    flexrio.module.io ready 0 

    • If multiple modules exist, the index must match the module instance. After restoring the name:
    • Rebuild the FPGA bitfile
    • Deploy again
    • Rerun the host VI, Validate CLIP Integration

  2. Check in the LabVIEW project:

    • The CLIP XML file includes the IO Ready signal
    • The signal appears under the FlexRIO device
    • Signal names have not been manually modified

Related Links

Wait for IO Ready - NI

Component-Level Intellectual Property (CLIP) - NI

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