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fpga compilation error

Hi all


I am developing the labview code for my application and I have faced the following problem:


I have a PXI system with 2 fpga cards (7854R and 7851R) for adquiring 13 fast analog signals. I finished the work related to the 7854R and everything was working OK. Now I am working in the 7851R, whose code is much simpler than the one in the 7854R. However, I cannot compile the I got a error, that can be checked in the report attached. This VI can be compiled without problems when it is included in a new empty project, so I assume there is no problem in the VI itself. I have tried to set smaller FIFO and Data Buffers for this FPGA, but cannot compile either. 


Could you give some advice to find what is really happening here? 


Thanks in advance,



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HI all


I have created an empty project where I have included both FPGA's, and the compilation of the 7851R also fails. When I check the target memory under the sub-menu "target/utilities/target information" I can see the following information:


Total Memory: 3380724 K

Free Memory: -917614 K


Could that be the source of the problem?


Thanks in advance





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Hi all 


After some testing, I have realized that the problem is located in the number of BLOCK RAMs used in the device.


The FPGA card only is able to handle maximun 4 16-bit signals, which needs 31 block rams. Firstly I was putting 8 signals, so there is no place for all that information in the FPGA 7851R. It is possible to use the 8 signals if the data buffer is changed to 8-bit type.


My question is now how important will be the reduction in resolution (precision) if I move to 8-bit data buffer. The data corresponds to 4 injector pressure sensors and 4 injector current measurements.



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Hi Pablo,


A comparison on numerical data types can be found here.



EDIT: My reply below was written to your post ‎2014-03-07 10:41 AM:


You are correct, it looks like the program you are synthesizing is to large for the FPGA. Could you please verify by deploying a smaller program?


One of the last entries in the error log states that 

"ERROR:Map:237 - The design is too large to fit the device. Please check the
Design Summary section to see which resource requirement for your design
exceeds the resources available in the device."


There are some more information about the FPGA in the NI PXI-7851R Data Sheet, I have extracted the most relevant information for you below:

NI 7841R/7851R

FPGA type

  Virtex-5 LX30

Number of flip-flops


Number of 6-input LUTs


Number of DSP48 slices (25 × 18 multipliers)


Embedded block RAM


1,152 kbits


You can always check the different Reports in the Compilation Status window for resource utlization information on your current project.


Best regards,

Robert P-F
Applications Engineer
National Instruments
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