Performance on LabVIEW Real-Time

NI-Serial users on LabVIEW Real-Time have control over whether secondary interrupt handling is enabled. When secondary interrupt handling is enabled, I/O is processed at a priority lower than time-critical. Using secondary interrupt handling reduces jitter for time-critical loops and makes serial hardware interrupts more deterministic. However, it may also reduce I/O performance and can increase the possibility of overflowing the RX FIFO buffer. Secondary interrupt handling is a setting at the system-wide level and is enabled by default.

To enable or disable this feature, complete the following steps:

1. Copy to your host the niserial.dbs file in the /ni-rt/system directory on the RT target.
2. In the niserial.dbs file, find the entry SecondaryInterrupts and modify it accordingly:
   • To enable secondary interrupt handling, set SecondaryInterrupts to 1.
   • To disable secondary interrupt handling, set SecondaryInterrupts to 0.
3. Download the updated niserial.dbs file to the target, overwriting the existing file in the /ni-rt/system directory.
4. Reboot your RT target.