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Using CompactRIO Scan Mode with Unsupported Backplanes

Primary Software: Driver Software>>NI-RIO
Primary Software Version: 1.0
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I have a NI 9014 controller and a NI 9101 chassis. I know that the Scan Interface Mode requires a chassis with at least a 2M Gate FPGA. Is there a way to get this working on an unsupported chassis?

Solution:
Yes, it is possible to use CompactRIO Scan Mode with an unsupported backplane with a few additional steps. To use cRIO Scan Mode with an unsupported backplane, it requires LabVIEW FPGA to compile in support for specific slots as the FPGA logic for a full Scan Mode interface will not fit on unsupported backplanes. A full Scan Mode is considered to be a full chassis with any combination of supported modules. This procedure does require LabVIEW FPGA and a compile, but no FPGA programming.
  1. Add a cRIO controller that supports Scan Interface to your project
  2. Add a the cRIO backplane to your project
  3. Right-click on the Chassis item and select New » C Series Modules
  4. Add the modules desired to the project
  5. Repeat steps 3 and 4 for addtional modules
  6. Right-click on the Chassis item and select New » FPGA Target
  7. Right-click on the FPGA target and select New » VI
  8. Save and compile the blank FPGA VI 
When you compile this blank FPGA VI, it will pull in the required FPGA logic to support CompactRIO Scan Mode in the slots that have modules under the chassis item.   If your FPGA VI fails to compile due to overmapping, the chassis and module configuration you are using will not work.  Remove one of the modules and compile the FPGA VI again.

Next, open and run the FPGA VI using the Open FPGA Interface function before your read/write to any I/O variables so the FPGA application and scan logic is deployed to the cRIO.

Note: This only applies to smaller cRIO backplanes that do not support the full scan mode (9101, 9072, etc).  sbRIO does not support scan mode in any way.



Related Links:
Developer Zone Tutorial: Using NI CompactRIO Scan Mode with NI LabVIEW Software
Developer Zone Tutorial: The RIO Scan Interface Under the Hood 
Developer Zone Tutorial: C Series Modules Supported by CompactRIO Scan Mode

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Report Date: 11/13/2008
Last Updated: 01/29/2010
Document ID: 4RCFASLX

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