Error -200251: "No DMA Channels or USB Bulk Endpoints Are Available" When Using Multiple Counters

Updated Sep 24, 2019

Reported In


  • PCI-6602
  • PXI-6602
  • PCI-6601
  • PXI-6608

Issue Details

I am doing more than three simultaneous counter input tasks on a PXI-6602 or PXI-6608, or I am doing more than one simultaneous counter input task on a PCI-6601.

After adding an additional task and running I receive error -200251 at DAQmx Start Task that states No DMA channels or USB Bulk Endpoints are available. How do I resolve this?


The PXI-6602 and PXI-6608 have three DMA channels and the PCI-6601 has one DMA channel. Any additional operations, including counter inputs, must be interrupt-based and cannot use DMA.

For instructions on configuring the particular task to use interrupts, refer to Configuring the Data Transfer Mechanism (Interrupts or DMA) in DAQmx and Traditional DAQ