When use scan mode and FPGA simultaneously, why does the FIFO Read can not be used?

Question

Hello, I am using compactRIO-9025 to do a project and trying to use scan mode and FPGA simultaneously ( Hybrid mode). I have already build a project as the following tutorial.
http://digital.ni.com/public.nsf/allkb/0DB7FEF37C26AF85862575C400531690 and I have NI 9205, NI 9023 in Scan mode and NI 9871 in FPGA mode in the same project.
In the FPGA Target of the project,  I add a FIFO and tried to use it to log in data from NI 9871. I wired the module I/O node to FIFO Write in the target vi. However, when I  droped the invoke method to the block diagram of the host vi and right clicked it, there is no FIFO Read can be choose. Could you please help me to solve this problem?
Thank you very much!!

Answer 1

I am not aware that using the Scan Engine is blocking any access to a transfer FIFO. But please reread this from your quoted KB:
Secondly, the number of DMA FIFO's that can be used in the FPGA code will be reduced, since the scan engine uses two DMA FIFO's. Most FPGAs have 3 DMA FIFO's, so there will only be one DMA channel left to use in the FPGA code.
This means, you have only a single DMA FIFO left which is either Target to Host or Host to Target.
Make sure that you configured the FIFO to be the correct direction for your needs...
hope this helps,
Norbert
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.