Hi Stu E,
Error codes can be found in the following location for the 5640R instrument driver and NI-RIO:
C:\Program Files\National Instruments\Shared\Errors\English
However when using LabVIEW FPGA to program the 5641R/40R the error code is more likely to come from NI-RIO or LV-FPGA. I am unaware of any overriding documentation outlineing the error codes for each prodcut. Is this needed for a specific task? Perhaps more information on what you are trying to accomplish would help clarify the need for this information.
JaceD
Signal Sources Product Support Engineer
National Instruments