Errors -201399 or -201105 When Using C Series Serial Digital Modules

Updated Jul 29, 2026

Reported In

Hardware

  • Digital I/O Device

Issue Details

  • When I try to run multiple tasks on my NI-9403 or another C Series digital module, I receive the following error:
    Error -201105: Resource requested by this task has already been reserved by a different task with conflicting settings. Unreserve any other tasks using this device, or change their settings to be compatible with this task.
  • When I start a task that contains multiple C Series digital modules, I receive Error -201399.

Solution

C Series digital modules are categorized based on how they communicate with the chassis backplane:
  • Serial modules transfer input or output data serially between the chassis backplane and the module.
  • Parallel modules transfer input or output data in parallel between the chassis backplane and the module.
An individual hardware-timed task can contain only one module type. Do not mix serial and parallel modules within the same hardware-timed task.
 
Serial modules support buffered tasks in a single direction, either input or output, beginning with NI-DAQmx 9.3. Because data is transferred serially, serial modules cannot route timing or trigger signals.
 
To prevent Error -201105 and Error -201399, follow these guidelines:
  • Do not use serial and parallel modules together in the same hardware-timed acquisition task.
  • Do not use serial modules as trigger sources.
  • Do not run a static task and a timed task simultaneously on the same serial module.
  • Do not use hardware timing in both input and output directions simultaneously on a bidirectional serial module.
  • Ensure your application does not run conflicting hardware-timed and software-timed tasks on the same serial module.
Following these restrictions prevents resource reservation conflicts and task configuration errors.

Additional Information

Parallel modules can perform clocked digital tasks and have access to chassis PFI lines for routing timing and triggering signals. Serial modules do not support this capability because of their communication architecture.