Why are NI Functional Safety Module Variables Read-Only in a CompactRIO Program?

Updated Dec 11, 2023

Reported In

Hardware

  • NI-9350
  • NI-9351

Issue Details

I am using the NI-9350 or NI-9351 Functional Safety Modules. I have programmed the logic within the module and I am currently monitoring the variables from the CompactRIO program. Why am I only able to read and not write the variables that come from the Functional Safety Modules?

Solution

The Functional Safety Modules are IEC 61508 safety integrity level (SIL) 3 rated. However, a CompactRIO running user-created LabVIEW code is not SIL-3 rated. If the CompactRIO controller was able to control the NI-9350/9351 variables, this would remove the SIL-3 rating from the NI-9350/9351.

Additional Information

Note: The C Series Functional Safety Modules are no longer sold by NI.

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