How Many DMA Channels Does My Data Acquisition (DAQ) Device Have?

Updated Aug 8, 2018

Reported In

Hardware

  • PCI-6013
  • PCI-6014
  • PCI-6023E
  • PCI-6024E
  • PCI-6025E
  • PXI-6030E
  • PXI-6031E
  • PCI-6154
  • PXIe-6124

Issue Details

How many DMA channels does my Data Acquisition (DAQ) device have?

Solution

The number of DMA channels depends on the DAQ device.
 
  • X Series
X Series devices have 8 DMA controllers, one for each of the following measurement and acquisition blocks:
  • Analog Input
  • Analog Output
  • Counter 0
  • Counter 1
  • Counter 2
  • Counter 3
  • Digital Waveform Generation (Digital Output)
  • Digital Waveform Acquisition (Digital Input)
  • M Series
M Series devices have 6 fully-independent DMA controllers for high-performance data block transfers. Each controller has a dedicated DMA channel that is used to transfer information between the card and system RAM. One DMA controller is available for each of the following measurement and acquisition blocks:
  • Analog Input
  • Analog Output
  • Counter 0
  • Counter 1
  • Digital Waveform Generation (Digital Output)
  • Digital Waveform Acquisition (Digital Input)
  • S Series
The majority of S Series devices have 3 DMA channels; however, there are a couple of exceptions. The PCI-6154 and the PXIe-6124 have 4 and 6 DMA channels, respectively.
 
  • E Series
Most of our E Series boards have 3 DMA channels with the exception of our Low-Cost Multifunction DAQ boards, which have 1 DMA channel. PCMCIA DAQCards and USB DAQPads do not use DMA. The table below shows most E-Series boards and the number of DMA channels provided by each.
 


 

Additional Information

DMA Overview
Today’s PCs are capable of programmed I/O and interrupt data transfers. DMA transfers increase the system throughput by using dedicated hardware to transfer data directly into system memory. Using this method, the processor is not burdened with moving data and is therefore free to engage in more complex processing tasks. To reap the benefits of DMA or interrupt transfers, your DAQ device must be capable of these transfer types. For example, while PCI and FireWire devices offer both DMA and interrupt-based transfers, PCMCIA and USB devices use interrupt-based transfers. Depending on how much processing is needed during data transfer, the rate at which the data is transferred from the DAQ device to PC memory may be affected by the data transfer mechanism.

With National Instruments driver software the DMA routines to transfer waveform data across the PC bus are optimized, thus providing the ability to transfer data as fast as possible. Each DMA controller channel contains a First-In First-Out memory storage (FIFO) and independent processes for filling and emptying the FIFO. This allows the buses involved in the transfer to operate independently for maximum performance.The DMA controller supports burst transfers to and from the FIFO. DMA controllers also act as a PCI Master device, and support scatter-gather operations to and from host memory. Each DMA controller supports packing and unpacking of data through the FIFOs to connect differently sized devices. The DMA system as a whole optimizes PCI bus utilization and automatically handles unaligned memory buffers, which can be used in linear or circular fashion.

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