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Determining the Number of DMA Channels for an NI FPGA Target

Updated Aug 1, 2023

Reported In

Hardware

CompactRIO Controller
CompactRIO Single-Board Controller

Software

LabVIEW FPGA Module

Issue Details

I would like to use Direct Memory Access (DMA) to transfer data from my FPGA target to my host (or vice versa), but I am not sure how many DMA Channels or FIFOs are on my FPGA target. How can I find out how many are available?

Solution

The table below provides a summary of the number of DMA Channels available on NI FPGA hardware.
Note: The selection of the DMA channel is done automatically in LabVIEW 8.6 FPGA Module and later.

Model Number	DMA FIFO Channels
FlexRIO 797x	32
cRIO-904x cRIO-903x cRIO-906x NI 9147 NI 9149 PCIe-1473 FlexRIO 796x myRIO PXIe-782xR PXIe-784xR PXIe-785xR sbRIO-9607 sbRIO-9627 sbRIO-9637 sbRIO-9651 USRP-294xR	16
cRIO-9075 cRIO-9076 sbRIO-9605 sbRIO-9606 sbRIO-9623 sbRIO-9626 sbRIO-9633 sbRIO-9636 NI 9146	5
PCI-5641 IF-RIO PCI-5640R IF-RIO	4
PXI-795x Most Other RIO Targets*	3

Note: This might not be a complete list. You can find the number of DMA channels in the specifications of each device.
Note: With version 2021 of LabVIEW, NI decided to reserve one DMA channel of some PXIe cards (R Series, FlexRIO) for other usages like HMB. Therefore, you can use one DMA channel less than specified in the specification sheet.

Additional Information

With the release of LabVIEW FPGA Module 2011, the number of DMA Channels is now accessible to the user via LabVIEW as well. From the Project Explorer you can discover DMA information about your FPGA targets including CompactRIO, R Series, and FlexRIO. Complete the following steps to access this information:

Open your FPGA Project

Right-click on the FPGA Target and select Properties

In the General tab scroll down until you can read the information about Number of DMA Channels

Note: Remember that when you use the FPGA in Scan Mode or Hybrid Mode, two of the DMA channels are reserved for the Scan Engine.

These steps can be followed even if you do not have access to the physical hardware. You can create a project and add your FPGA target to project as New targets or devices instead of Existing targets or devices.

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