Missing Methods For Memory Error When Using FPGA Host Memory Buffer

Updated Dec 1, 2017

Reported In

Hardware

  • sbRIO-9637
  • cRIO-9068
  • sbRIO-9651
  • sbRIO-9627
  • sbRIO-9607

Software

  • LabVIEW 2017 FPGA Module

Driver

  • NI CompactRIO 17.0

Issue Details

I would like to take advantage of Host Memory Buffer functionality in LabVIEW FPGA, thus I created a Memory in the LabVIEW project under the FPGA target and set implementation to DRAM in General page of Memory Properties Dialog Box.
Then, in the LabVIEW FPGA VI block diagram, I placed Write (Memory Method) and then I run the VI to launch compilation process.
However, compilation failed immediately after Generating Intermediate Files step, returning the following Code Generation Error:

Missing Method(s) for DRAM-based memory

The following method(s) are missing for Memory: Write. All DRAM-based memory items require Write, Request Data and Retrieve Data methods.

 

Solution

As the error message explains, when using DRAM-based memory items, you need to place in your LabVIEW FPGA code all three memory methods supported for this interface: Write Data, Request Data, Retrieve Data. All methods needs to be placed inside a Single Cycle Timed Loop (SCTL).
 

Additional Information

Host Memory Buffer support was released in NI CompactRIO 17.0 with initial support on the cRIO-9068, sbRIO-9607, sbRIO-9627, sbRIO-9637, sbRIO-9651 (SOM). We plan to support more targets in future releases.
 

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