Two NI-DAQmx Read attributes/properties allow you to check if the PLL was unlocked during data acquisition for a task. The first is PLL.UnlockedChansExist. This attribute/property returns a Boolean true if one or more channel PLLs became unlocked during the previous acquisition. The second is PLL.UnlockedChans. This attribute/property returns an array of strings indicating which channel PLLs (if any) became unlocked.
PLL.UnlockedChansExist can only be used when the task is in a stop state but is still reserved. You can also explicitly commit, start, and then stop the task without explicitly uncommitting using the DAQmx Control Task VI.