What happens to FPGA code when a module it expects is missing?

Question

Hi Folks,
I want to know what happens if you have FPGA code that expects a module to be present running on a system where the module is missing.
We have a RT control system that runs on a cRIO 9014 with a 9111 backplane. There are only two modules in the slots and one of these is the Prosoft Profibus module. The biggest chunk of the FPGA code is taken up with configuring and sending and receiving using this module. Specifically the communications with the module are done by the Read (Memory) and Write (Memory) structures.
We are developing code to use the Ethernet/IP libraries instead of Profibus in some cases. This means the communications moves from the FPGA to the RT. We are considering have the ability to switch be an option.
My concern is that if the FPGA has code in that references the Profibus module, then it might behave badly if the module is not present.
And so my question is if FPGA code tries to reference a module that is not present, what happens? Is it just an error? Will there be no error? What?
Thanks!

Answer 1

I am not familiar with profibus, but why not just remove the module and run it and see what happens? I'm guessing you will get an error, althougth which error I am not sure. 
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