Configuring the NI 9401 for Simultaneous Input/Output

Updated Nov 15, 2017

Reported In

Hardware

  • NI-9401
  • sbRIO-9401

Issue Details

I know that the NI 9401 has eight digital lines. Can this module be used for counter inputs, digital inputs and digital outputs simultaneously or concurrently? Can it work bidirectionally?

Solution

The 9401 can be configured for directional line measurements by nibble (a nibble is the name given to a group of 4 channels). Each group of four channels (channels 0-3 and channels 4-7) must be configured to either input or output.  All channels may be input, all may be output, or one nibble may be input with the other nibble set to output. The channels cannot be configured individually.

Using The NI-9401 in a cDAQ Chassis

When used in a CompactDAQ 9172 chassis, you can use counter inputs with a nibble set to input, and counter outputs with a nibble set to output.

Using The NI-9401 in a cRIO Chassis

When using the NI 9401 in a CompactRIO chassis, the way to configure the module for input or output is as follows:
  • The initial input/output configurations can be configured from the module properties dialog box. To get to module properties, right click on the module in the Project Explorer and click Properties.
  • You can also change the direction of the lines programmatically using I/O method nodes. You can create a method by going in the Functions Palette and selecting Programming » FPGA I/O » I/O Method. Once you place the method, right-click it and go to Select Item » Mod(x). Now click on Method and select Select Line Direction.

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