RT Parallel FPGA Reference

[tcapuano-aps]

Hi,

Can anyone explain to be the ramifications of having multiple parallel loops all accessing the same open FPGA reference? As an example, this technique is used in the CompactRIO Project Template.

Are there any hidden mutexs on the reference? What happens if multiple loops all try and read from the same variable?

Thanks,

Tom

[Terry_ALE]

The ability to access the same FPGA VI reference is benefit. Often times we access data or FIFOs from more than one loop.

The system should be designed to not try to set values from more than one loop. 

[tcapuano-aps]

Thanks for the reply.

So, no hidden gotchas?

[Terry_ALE]

Your comment reminded me what a wise friend told me once. "you always need to know the gimmies and gotchas of any technology."

Ask about more scenarios that you are concerned about being gotchas and we'll analyze them here.

[tcapuano-aps]

Thanks Terry,

I don't have any particular concerns. I have seen plenty of code that does it, but I have never found a detailed reference going into how the reference actually works under the hood. I just don't want to accidentally run into some resource contention.

Tom

[Terry_ALE]

These are my FPGA VI reference links:

1. Open and Close of LabVIEW FPGA VI References

   1. http://zone.ni.com/reference/en-XX/help/371599M-01/lvfpgahost/open_fpga_vi_reference/

   2. http://zone.ni.com/reference/en-XX/help/371599M-01/lvfpgahost/close_vi_reference/

2. Opening a Reference to an FPGA VI, Build Specification, or Bitfile (FPGA Interface)

   1. http://zone.ni.com/reference/en-XX/help/371599M-01/lvfpgahosthelp/fpga_opening_vi_reference/

3. Open Dynamic Bitfile Reference Function

   1. http://zone.ni.com/reference/en-XX/help/371599M-01/lvfpgahost/open_dyn_bitfile_reference/

4. Multiple FPGA VI References

   1. https://zone.ni.com/reference/en-XX/help/371599P-01/lvfpgahosthelp/multiple_fpga_refs/

[tcapuano-aps]

Thanks. Primarily, reference 4 is some of the information I want.

Personally, I would like more information about the last sentence:

"The only type of access that you can always make safely using multiple FPGA VI references is reading controls and indicators."

I am looking for more information on the other not "always" cases.

Regards,

Tom

[Terry_ALE]

There are NI presentations (which I cannot find) which talk about maximum number of references and other technical details.

I would check the same help article under newer versions of LabVIEW and see if there is anything new.

Which reminds me that NI has not updated online help links since 2018.  We are always linking people to 2018 help.  This problem has been taken up with NI here: https://forums.ni.com/t5/Feedback-on-NI-Community/User-manuals-not-updated-on-NI-site/td-p/4160150.