NI Scan Engine Faults

Targets with the NI Scan Engine installed use faults to address asynchronous error conditions. LabVIEW distinguishes three fault levels: minor, major, and unrecoverable. LabVIEW logs all faults in the NI Distributed System Manager.

Note  Some I/O hardware drivers implement fault handling behavior in response to major faults. Refer to the specific hardware documentation for information about fault handling behavior.

Examples of minor faults include startup errors, which can occur when the controller is unable to apply its saved configuration on startup. If LabVIEW detects that the scan engine has run late, LabVIEW triggers major fault −66460. If LabVIEW detects ten consecutive late scan iterations, LabVIEW triggers major fault −66461 and the NI Scan Engine stops running. Unrecoverable faults can occur due to a hardware failure or software crash. In the event of an unrecoverable fault, reboot the controller and contact National Instruments.

Viewing and Clearing Faults

Use the NI Distributed System Manager to view and clear faults. You also can use the Get Fault List VI and the Clear Fault VI to view and clear faults programmatically.

System Faults

LabVIEW defines a set of common faults and you can log additional faults based on LabVIEW error clusters. Fault codes are grouped together by type, as shown in the following table.

Fault Type	Range of Fault Codes
I/O Scan Driver Errors	−66000 through −66099
I/O Variables	−66200 through −66299
NI Scan Engine VIs	−66300 through −66399
NI Scan Engine	−66400 through −66499
User Fault	Any LabVIEW error code

User Faults

You can use the Set Fault VI to trigger minor or major user-defined faults based on LabVIEW error codes. LabVIEW reserves a memory pool large enough to log up to 100 unique fault codes. If you exceed 100 unique fault codes, LabVIEW triggers minor fault −66420 and discontinues logging additional faults. However, even if the maximum number of user faults has been reached, a major or unrecoverable fault can still trigger hardware drivers to initiate fault handling behavior.

Note  Refer to the specific hardware documentation for information about fault handling behavior.